Like other infectious diseases, malignant catarrh pursues a longer or shorter course in accordance with the severity of the attack. In acute cases death is said to take place three to seven days after the appearance of symptoms. Recovery, if it occurs, may take three or four weeks. According to statistics, from 50 to 90 per cent of the affected animals die.

If animals which have died of this disease are examined, in addition to the changes of the mucous membrane of mouth and nasal cavities referred to above, shallow ulcers in these situations will be found occasionally. These necrotic processes may pass beneath the mucous membrane and even involve the underlying bony structure. In severe cases membranous (croupous) deposits are found in the throat. Similar deposits have been found upon the mucous membrane of the fourth stomach and intestine, which is always inflamed. There is more or less inflammation of the membranes of the brain, kidneys, and liver, and some fatty degeneration of the voluntary muscles. In countries where rinderpest occasionally appears it may be difficult to distinguish between it and malignant catarrh, owing to a general similarity of the symptoms. The principal points to be observed in differentiating between the two are the very slight transmissibility of the latter as compared with the intense contagiousness of the former, and the tendency of malignant catarrh to run a more chronic course than rinderpest, which usually results fatally in a very few days. Only a trained veterinarian who takes into consideration all the different symptoms and lesions of both diseases should decide in such cases.

Treatment.—There is no specific treatment for this affection. Copious blood letting in the earliest stages has been highly recommended, however, as this has a tendency to deplete the system and lessen the exudation of inflammatory products. Antiseptic washes, such as 4 per cent boric-acid solution to the eyes and Dobell's solution applied to the nose and mouth with ice poultices over the crest of the head and frontal region, have also proved efficacious. Calomel should also be given in 1-dram doses twice a day for three days, and in severe cases, involving the respiratory tract, a powder containing ferrous sulphate, quinin, and subnitrate of bismuth, given twice a day, will be found beneficial. At the same time it must be remembered that much greater success is to be looked for in the preventive treatment. This consists in the removal of the healthy from the infected animals (not vice versa) and thorough cleaning and disinfecting of the contaminated stables. If the floors are low and damp, they should be raised and made dry. If this can not be done, place a layer of cement under the stable floor to prevent water from entering from below. The stable should be well ventilated and the soil in the pastures thoroughly drained. If this is carefully carried out, the contagion should be destroyed and the danger of the reappearance of the disease in a great measure lessened.

MALIGNANT EDEMA.

Malignant edema, also termed gangrenous septicemia, is an acute, inflammatory disease of domestic and wild animals, resulting from the introduction of a specific organism into the deep connective tissues of a susceptible animal and proving fatal in many instances within 24 to 48 hours. The disease may be inoculated from one animal to another, but only by inserting the virus deeply below the skin. It is infrequently met with in cattle, but may follow operating wounds, as roweling, castration, and phlebotomy, which have become infected with septic matter, soil, or unclean instruments. In the pathological laboratory of the Bureau of Animal Industry the organism has also been obtained from the infected muscles of a calf that was supposed to have died of blackleg, and, as a result, all blackleg virus is thoroughly tested before it is made into blackleg vaccine in order to exclude the malignant-edema organism. The essential cause of malignant edema is a long, slender, motile, spore-bearing bacillus, resembling the bacillus of blackleg, and which can develop only in the absence of the atmosphere. Unlike the bacilli of anthrax and blackleg, which are confined to certain districts, this organism is widely distributed and found in ordinary garden soil, foul water, and in the normal intestinal tract of the herbivora. It may be brought to the surface of the soil by growing plants, rains, winds, or burrowing insects and rodents. In animals that have succumbed to the disease the germ is confined to the seat of infection, but a few hours after death it may migrate through the blood channels to other parts of the body. The bacillus may attack man, horses, asses, goats, sheep, pigs, cats, dogs, and poultry. Adult cattle, although refractory to experimental inoculation, suffer from natural infection, while calves are susceptible to both these methods of exposure. (Kitt.) The introduction of the bacillus into abrasions of the skin and superficial sores rarely does any harm, because the germ is quickly destroyed by contact with air. If, however, the organisms are inserted deeply into the subcutaneous tissues of susceptible animals, they quickly develop, producing a soluble poison, which is the fatal agent.

In lamb-shearing season, or after docking or castration, the mortality is higher among these animals because of wounds inflicted at such times. The application of antiseptics to wounds thus made will reduce the percentage of deaths to a minimum.

Symptoms.—Usually the first symptoms are overlooked. In the early stages the animal appears listless, disinclined to move about, and lies down in shady and quiet places. If forced to move about, the hind legs are drawn forward with a peculiar, stiff, dragging movement, and there may be slight muscular trembling over all the body, which becomes more intense as the disease progresses. When driven, the animal shows signs of fatigue, ultimately dropping to the ground completely exhausted. Breathing becomes fast and painful, with frequent spasmodic jerks.

The pulse is quick and weak and the temperature is 106 deg. to 107 deg. F. An edematous, doughy, and painful swelling appears at the point of infection. This tumefaction spreads more and more, and crackles on pressure. In case of an open wound, a fetid liquid and frothy discharge is observed. The center of the swelling may appear soft and jellylike, while the margin is tense, hot, and painful. The symptoms increase rapidly, resulting in coma and death.

Lesions.—After death the fat and subcutaneous tissues surrounding the infected area are infiltrated with a yellow gelatinous material containing an orange-colored foam, due to the presence of gas bubbles.

The muscles at this point are friable, spongy, and of a uniform brownish tint, dissociated by gas and with a blood-tinged exudate. This gangrenous tissue, when present before death, can be removed without pain to the animal. The intestines are generally normal, but, together with the peritoneum, they may be inflamed, and the lungs are usually the seat of an edema. The spleen, liver, and kidneys retain their normal appearance, in marked contrast with anthrax.

Differential diagnosis.—Unlike blackleg, this disease never appears as an epizootic but in isolated cases. It may also be differentiated from the former by the history of a recent parturition or surgical operation, by the presence of an external injury at the site of the swelling accompanied with a fetid liquid discharge, and the gangrenous appearance of the tumefaction. Man is susceptible to malignant edema, but not to blackleg. Malignant edema may also be easily differentiated from anthrax in that the blood and spleen are normal in appearance, while in the latter disease the blood is dark and of a tarlike consistency, and the spleen appears swollen, injected, and softened. The local tumor in malignant edema contains gas bubbles, which are absent in anthrax swellings. Inoculation experiments of guinea pigs, rabbits, and chickens will also disclose the differences among the above-mentioned three diseases, since all these species are killed by the germ of malignant edema, only the first two species by the anthrax bacillus, while the guinea pig alone will succumb to the blackleg infection.

Treatment.—Treatment is chiefly surgical and consists in laying the infected areas wide open by free incision, followed by a liberal application of a 30 per cent solution of hydrogen dioxid and subsequently a 5 per cent solution of carbolic acid. Usually the disease when observed has advanced to such an extent that medicinal interference is without avail. Preventive treatment is by far the most desirable, and consists, essentially, in a thorough disinfection of all accidental and surgical wounds, the cleansing of the skin, and the exclusion of soil, filth, and bacteria during surgical operations of any nature. Sheds, barns, and stables should receive a thorough application of quicklime or crude carbolic acid wash after all rubbish has been removed and burned. All dead animals should be burned or deeply buried and covered well with quicklime.

SOUTHERN CATTLE FEVER (TEXAS FEVER, TICK FEVER).

[Pls. XLIV-XLIX.]

This disease, which is more commonly known as Texas fever, and sometimes as splenetic fever, is a specific fever communicated by cattle which have recently been moved northward from the infected district; it is also contracted by cattle taken into the infected district from other parts of the world. It is characterized by the peculiarity among animal diseases that the animals which disseminate the infection are apparently in good health, while those which sicken and die from it do not, as a rule, infect others.

It is accompanied with high fever, greatly enlarged spleen, destruction of the red blood corpuscles, escape of the coloring matter of the blood through the kidneys, giving the urine a deep-red color, with a yellowness of the mucous membranes and fat, which is seen more especially in fat cattle, by a rapid loss of strength, and with fatal results in a large proportion of cases.

This disease has various names in different sections of the country where it frequently appears. It is often called Spanish fever, acclimation fever, red water, black water, distemper, murrain, dry murrain, yellow murrain, bloody murrain, Australian tick fever, and tristeza of South America.

The earliest accounts we have of this disease date back to 1814, when it was stated by Dr. James Mease, before the Philadelphia Society for Promoting Agriculture, that the cattle from a certain district in South Carolina so certainly disease all others with which they mix in their progress to the North that they are prohibited by the people of Virginia from passing through the State; that these cattle infect others while they themselves are in perfect health, and that cattle from Europe or the interior taken to the vicinity of the sea are attacked by a disease that generally proves fatal. Similar observations have been made in regard to a district in the southern part of the United States.

The northern limits of this area are changed yearly as a result of the dissemination or eradication of the cattle tick along the border, but the infected area has gradually decreased, owing to the successful endeavors pushed forward to eliminate the ticks.

It was the frequent and severe losses following the driving of cattle from the infected district in Texas into and across the Western States and Territories which led to the disease being denominated Texas fever. It is now known, however, that the infection is not peculiar to Texas or even to the United States, but that it also exists in southern Europe, Central and South America, Australia, South Africa, and the West Indies.

When cattle from other sections of the country are taken into the infected district they contract this disease usually during the first summer, and if they are adult animals, particularly milch cows or fat cattle, nearly all die. Calves are much more likely to survive. The disease is one from which immunity is acquired, and therefore calves which recover are not again attacked, as a rule, even after they become adult.

When the infection is disseminated beyond the permanently infected district, the roads, pastures, pens, and other inclosures are dangerous for susceptible animals until freezing weather. The infection then disappears, and cattle may be driven over the grounds or kept in the inclosures the succeeding summer and the disease will not reappear. There are some exceptions to this rule in the section just north of the boundary line of the infected district. In this locality the infection sometimes resists the winters, especially if they are mild.

In regard to the manner in which the disease is communicated, experience shows that this does not occur by animals coming near or in contact with one another. It is an indirect infection. The cattle from the infected district first infect the pastures, roads, pens, cars, etc., whence the susceptible cattle obtain the virus secondhand. Usually animals do not contract the disease when separated from infected pastures by a fence. If, however, there is any drainage or washing by rains across the line of fence this rule does not hold good.

The investigations made by the Bureau of Animal Industry demonstrate that the ticks which adhere to cattle from the infected district are the only known means of conveying the infection to susceptible cattle. The infection is not spread by the saliva, the urine, or the manure of cattle from the infected district. In studying the causation and prevention of this disease, attention must therefore be largely given to the tick, and it now seems apparent that if cattle could be freed from this parasite when leaving the infected district they would not be able to spread the malady. The discovery of the connection of the ticks with the production of the disease has played a very important part in determining the methods that should be adopted in preventing its spread. It established an essential point and indicated many lines of investigation which have yielded and are still likely to yield very important results.

Nature of the disease.—Texas fever is caused by an organism which lives within the red blood corpuscles and breaks them up. It is therefore simply a blood disease. The organism does not belong to the bacteria but to the protozoa. It is not, in other words, a microscopic plant, but it belongs to the lowest forms of the animal kingdom. This very minute organism multiplies very rapidly in the body of the infected animal, and in acute cases causes an enormous destruction of red corpuscles in a few days. How it gets into the red corpuscle it is not possible to state, but it appears that it enters as an exceedingly minute body, probably endowed with motion, and only after it has succeeded in entering the corpuscle does it begin to enlarge. Plate XLV, figure 4, illustrates an early stage of this blood parasite. The red corpuscle contains a very minute, roundish body which is stained blue to bring it into view. The body is, as a rule, situated near the edge of the corpuscle. Figure 5 illustrates an older stage in the growth of the parasite, in fact the largest which has thus far been detected. It will be noticed that there are usually two bodies in a corpuscle. These bodies are in general pear-shaped. The narrow ends are always toward each other when two are present in the same corpuscle. If we bear in mind that the average diameter of the red blood corpuscles of cattle is from 1/4000 to 1/5000 inch, the size of the contained parasite may be at once appreciated by a glance at the figures referred to.

The various disease processes which go on in Texas fever, and which we may observe by examining the organs after death, all result from the destruction of the red corpuscles; this destruction may be extremely rapid or slow. When it is rapid we have the acute, usually fatal, type of Texas fever, which is always witnessed in the height of the Texas-fever season, that is, during the latter weeks of August and the early weeks of September. When the destruction of corpuscles is slower, a mild, usually nonfatal, type of the disease is called forth, which is only witnessed late in autumn or more rarely in July and the early part of August. Cases of the mild type occurring thus early usually become acute later and terminate fatally.

The acute disease is fatal in most cases, and the fatality is due not so much to the loss of blood corpuscles as to the difficulty which the organs have in getting rid of the waste products arising from this wholesale destruction. How great this may be a simple calculation will serve to illustrate. In a steer weighing 1,000 pounds, the blood in its body weighs about 50 pounds, if we assume that the blood represents one-twentieth of the weight of the body, which is a rather low estimate. According to experimental determination at the bureau station, which consists in counting the number of blood corpuscles in a given quantity of blood from day to day in such an animal, the corpuscles contained in from 5 to 10 pounds of blood may be destroyed within 24 hours. The remains of these corpuscles and the coloring matter in them must be either converted into bile or excreted unchanged. The result of this effort on the part of the liver causes extensive disease of this organ. The bile secreted by the liver cells contains so much solid material that it stagnates in the finest bile canals and chokes these up completely. This in turn interferes with the nutrition of the liver cells and they undergo fatty degeneration and perish. The functions of the liver are thereby completely suspended and death is the result. This enormous destruction of corpuscles takes place to a large extent in the kidneys, where a great number of corpuscles containing the parasites are always found in acute cases. This accounts largely for the blood-colored urine, or red water, which is such a characteristic feature of Texas fever. The corpuscles themselves are not found in the urine; it is the red coloring matter, or hemoglobin, which leaves them when they break up and pass into the urine.

Symptoms.—After a period of exposure to infected soil, which may vary from 13 to 90 days, and which will be more fully discussed under the subject of cattle ticks as bearers of the Texas-fever parasite, the disease first shows itself in dullness, loss of appetite, and a tendency to leave the herd and stand or lie down alone. A few days before these symptoms appear the presence of a high fever may be detected by the clinical thermometer. The temperature rises from a normal of 101 deg. to 103 deg. F. to 106 deg. and 107 deg. F. There seems to be little or no change in temperature until recovery or death ensues. The period of high temperature or fever varies considerably. As it indicates the intensity of the disease process going on within, the higher it is the more rapid the fatal end. When it does not rise above 104 deg. F. the disease is milder and more prolonged.

The bowels are mostly constipated during the fever; toward the end the feces may become softer and rather deeply tinged with bile. The urine shows nothing abnormal during the course of the disease until near the fatal termination, when it may be deeply stained with the coloring matter of the blood. (Hemoglobinuria; see Pl. XLV, fig. 3.) Although this symptom is occasionally observed in animals which recover, yet it may generally be regarded as an indication of approaching death. The pulse and respiration are usually much more rapid than during health.

Other symptoms in addition to those mentioned have been described by observers, but they do not seem to be constant, and only those described above are nearly always present. As the end approaches emaciation becomes very marked, the blood is very thin and watery, and the closing of any wound of the skin by clots is retarded. The animal manifests increasing stupor and may lie down much of the time. Signs of delirium have been observed in some cases. Death occurs most frequently in the night.

The duration of the disease is very variable. Death may ensue in from three days to several weeks after the beginning of the fever. Those that recover ultimately do so very slowly, owing to the great poverty of the blood in red corpuscles. The flesh is regained but very gradually, and the animal may be subjected to a second, though mild, attack later on in the autumn, which pushes the full recovery onward to the beginning of winter.

In the mild type of the disease, which occurs in October and November, symptoms of disease are well-nigh absent. There is little if any fever, and if it were not for loss of flesh and more or less dullness the disease may pass unnoticed, as it undoubtedly does in a majority of cases. If, however, the blood corpuscles are counted from time to time a gradually diminishing number will be found, and after several weeks only about one-fifth or one-sixth of the normal number are present. It is indeed surprising how little impression upon the animal this very impoverished condition of the blood appears to make. It is probable, however, that if two animals kept under the same conditions, one healthy and the other at the end of one of these mild attacks, are weighed, the difference would be plainly shown.

Pathological changes observable after death.—In the preceding pages some of these have already been referred to in describing the nature of the disease. It is very important at times to determine whether a certain disease is Texas fever or some other disease, like anthrax, for example. This fact can, as a rule, be determined at once by a thorough microscopic examination of the blood. The necessary apparatus and the requisite qualifications for this task leave this method entirely in the hands of experts. There are, however, a considerable number of changes caused by this disease which may be detected by the naked eye when the body has been opened. Put together they make a mistake quite impossible. The presence of small ticks on the skin of the escutcheon, the thighs, and the udder is a very important sign in herds north of the Texas-fever line, as it indicates that they have been brought in some manner from the South and have carried the disease with them, as will be explained later. Another very important sign is the thin, watery condition of the blood, either just before death or when the fever has been present for four or five days. A little incision into the skin will enable any one to determine this point. Frequently the skin is so poor in blood that it may require several incisions to draw a drop or more.

The changes in the internal organs, as found on post-mortem examinations, are briefly as follows: The spleen, or milt, is much larger than in healthy animals. It may weigh three or four times as much. When it is incised the contents or pulp is blackish (see Pl. XLIV, fig. 1), and may even well out as a disintegrated mass. The markings of the healthy spleen (fig. 2) are all effaced by the enormous number of blood corpuscles which have collected in it, and to which the enlargement is attributable. Next to the spleen the liver will arouse our attention. (See Pl. XLV, fig. 2.) It is larger than in the healthy state, has lost its natural brownish color (fig. 1), and now has on the surface a paler, yellowish hue. When it is incised this yellowish tinge, or mahogany color, as it has been called by some, is still more prominent. This is owing to the large quantity of bile in the finest bile capillaries, and as these are not uniformly filled with it the cut surface has a more or less mottled appearance. This bile injection causes in many cases a fatty degeneration of the liver cells, which makes the organ appear still lighter in color.

In all cases the gall bladder should be examined. This is distended with bile, which holds in suspension a large number of yellow flakes, so that when it is poured into a tall bottle to settle fully one-half or more of the column of fluid will be occupied by a layer of flakes. If mucus is present at the same time, the bile may become so viscid that when it is poured from one glass to another it forms long bands. The bile in health is a limpid fluid, containing no solid particles.

If the animal during life has not been observed to pass urine colored with blood or red water, the bladder should be opened. This quite invariably, in acute cases, contains urine which varies in color from a deep port wine to a light claret. In many cases the color is so dense that light will not pass through even a thin layer. (Pl. XLV, fig. 3.) The kidneys are always found congested in the acute attack. The disease exerts but little effect on the stomach and intestines beyond more or less reddening of the mucous membrane; hence an examination of them may be safely omitted. The lungs are, as a rule, not diseased. The heart usually shows patches of blood extravasation on the inside (left ventricle) and less markedly on the outer surface.

We have observed jaundice of the various tissues but very rarely. It has been observed by some quite regularly, however.

During the hot season about 90 per cent of the susceptible mature animals from a noninfected district die, but later, in the cool weather, the disease assumes a milder type, with a consequent decrease in the number of deaths.

The cattle tick, Margaropus annulatus, as the carrier of Texas fever. (Pls. XLVI, XLVII, and XLVIII.)—The cattle tick is, as its name indicates, a parasite of cattle in the southern part of the United States. It belongs to the group of Arthropoda and to the genus Margaropus (or Boophilus), which is included in the order Acarina. Its life history is quite simple and easily traced from one generation to another. It is essentially a parasite, attaching itself to the skin (Pl. XLVIII) and drawing the blood of its host. It is unable to come to maturity and reproduce its kind unless it becomes attached to the skin of cattle, whence it may obtain its food.

The eggs laid on the ground after the female has dropped from the host begin to develop at once. When the embryo is fully formed within the shell it ruptures this and gains its freedom. The time required from the laying of the eggs to their hatching varies considerably, according to the temperature. In the laboratory in the heat of midsummer this was accomplished in about 13 days. In the late fall, under the same conditions, it required from four to six weeks. The larva after emerging from the egg is very minute, six-legged, and is just visible to the naked eye. (Pl. XLVI, fig. 3.) If these larvae are kept on a layer of moist sand or earth in a covered dish, they may remain alive for months, but there is no appreciable increase in size. So soon, however, as they are placed upon cattle growth begins.

On pastures these little creatures soon find their way on to cattle. They attach themselves by preference to the tender skin on the escutcheon, the inside of the thighs, and on the base of the udder. Yet when they are very numerous they may be found in small numbers on various parts of the body, such as the neck, the chest, and the ears. (Pl. XLVIII and Pl. XLIX, fig. 1.)

The changes which they undergo during their parasitic existence were first studied by Dr. Cooper Curtice, of the Bureau of Animal Industry, in 1889. The young tick molts within a week, and the second or nymphal stage of the parasite's life is thus ushered in. After this change it has four pairs of legs. Within another week another molt takes place by which the tick passes from the nymphal to the sexual, or adult, stage. Impregnation now takes place, and, with the development of the ova in the body, the tick takes an increased quantity of blood, so that in a few days it becomes very much larger. That the rapid growth is due to the blood taken in may be easily proved by crushing one. The intestine is distended with a thick, tarry mass composed of partly digested blood. When the female has reached a certain stage of maturity she drops to the ground and begins to lay a large number of eggs, which hatch in the time given above.

The life of the cattle tick is thus spent largely on cattle, and although the young, or larvae may live for a long time on the ground in the summer season, they can not mature except as parasites on cattle and horses. We have purposely omitted various details of the life history, including that of the male, as they are not necessary to an understanding of our present subject—Texas fever. How this is transmitted we will proceed to consider. Before the enforcement of the Federal quarantine southern cattle sent north during the spring and summer months carried on their bodies large numbers of the cattle ticks, which, when matured, would drop off and lay their eggs in the northern pastures. After hatching, the young ticks would soon get upon any northern cattle which happened to be on the pasture. So soon as they attached themselves to the skin they inoculated the cattle, and Texas fever would break out a week or more thereafter. For many years there had been a growing suspicion that the cattle tick was in some way concerned in the spread of Texas fever, and the facts which supported this supposition finally became so numerous and convincing that a series of experiments was inaugurated by the Bureau of Animal Industry which served to show that the tick is abundantly able to carry the disease to a herd of healthy cattle, and, in fact, is probably the only agent concerned in the transmission of the disease from southern cattle to susceptible northern animals.

Injurious effects of cattle ticks.—Unfortunately many cattle owners who have always been accustomed to see both ticks and ticky cattle on their farms are not inclined to attach much importance to these parasites, and, as a rule, through lack of appreciation of their damaging effects, placidly consider them as of little consequence. That ticks may be detrimental to their hosts in several ways has probably not suggested itself to these stockmen, who are most vitally affected, and it therefore seems necessary to emphasize the fact that, in addition to their relation to Texas fever, they may also be injurious to cattle as external parasites. While the power of transmitting Texas fever is undoubtedly the most dangerous property possessed by the cattle tick and is the principal cause for adopting stringent measures looking to its complete eradication, nevertheless there still remain other good reasons for the accomplishment of this achievement. These secondary objections to the presence of ticks on cattle consists in the physical harm they do to the host aside from the production of the specific disease of Texas fever. True, a few parasites may remain on cattle indefinitely without causing any noticeable effect, but it is not uncommon to notice bovine animals on pastures with their hides heavily infested with these pests. In such cases it can readily be seen that the continuous sucking of blood causes more or less impoverishment of the circulation. The animal must therefore be fed more in order to meet the demands of the parasites in addition to the ordinary needs of the host. If the ticks are removed from the body, the bites inflicted are often distinguished by small, inflamed or reddened areas somewhat swollen, with perforations of the skin which may allow the entrance of various kinds of disease germs, and showing that more or less irritation of the hide is produced by these parasites. This condition, together with the loss of blood, frequently induces an irritable state and evidence of uneasiness commonly known as "tick worry," which results in the loss of energy and other derangements of the animal's health. It may in some cases, especially in hot weather, become so pronounced that the animal will lose flesh in spite of good pasturing, thereby reducing the vitality and rendering it more susceptible to the inroads of disease. Moreover, if the infestation of ticks is not controlled, the cattle may be so reduced in condition that growth is retarded, and, in the case of young animals, they may never become fully developed, but remain thin, weak, and stunted—a condition that has been termed "tick poverty"—and easily succumb to other diseases as a result of lowered vitality. In milch cows this debilitating influence of the numerous ticks is shown in a greatly reduced milk supply. This should not appear strange when it is considered that some animals harbor several thousand of the bloodsucking parasites. If these parasites are crushed, it will be found that their intestines are completely filled with a dark, thick mass of blood abstracted from the animal host and containing nutriment that should go to the formation of milk, flesh, and the laying on of fat. In some rare cases the large number of bites on a limited area of skin may be followed by infection with pus-producing organisms, giving rise to small abscesses which may terminate in ulcers. The discharge from these sores, or in some cases the mere oozing of blood serum through the incision made by the mouth parts of the ticks, keeps the hair moist and matted together, and the laying and hatching of fly eggs in these areas give rise to infestation with destructive maggots, causing ulcers and other complications that require medical treatment. These statements regarding the secondary injurious effects of cattle ticks also apply to those ticks which have been previously spoken of as harmless so far as Texas fever is concerned, and, in fact, to all external parasites. Therefore, it is just as important to eradicate the cattle ticks for reasons other than those associated with Texas fever as it is to exterminate lice, fleas, and other vermin. Furthermore, cattle ticks, aside from the losses sustained by their purely parasitic effects, are the greatest menace to the profitable raising and feeding of cattle in the South, because they are an obstacle to cattle traffic between the infected and noninfected districts.

Loss occasioned by cattle ticks.—The economic aspect of the tick problem is unquestionably of the greatest practical interest, since the fundamental importance of all the other questions which surround it depends upon the actual money value involved. A careful and conservative estimate made in 1916 placed the annual loss caused by the ticks in the United States at $40,000,000, and indicated that the ticks also lowered the assets of the South by an additional $33,000,000. The principal items in these losses are set forth below.

It is well known that those animals coming from an infected district and sold in the "southern pens" of northern stockyards bring about one-half a cent less per pound than the quoted market price. The handicap that is placed on the southern cattle raiser as a result of this decrease in value of his stock will average at this figure $3 per head, allowing an individual weight of 600 pounds for all classes of animals. This decreased value reacts and fixes the valuation of all cattle which remain in the infected territory, thereby reducing the assets of the cattle industry of that section. In addition there is a very great loss from the decrease in flesh and lack of development of southern cattle occasioned by the parasitic life of the ticks from without and by the blood-destroying and enervating properties of the protozoan parasites from within.

The presence of the tick among the cattle of the South not only lessens the value of the cattle on the hoof but causes the gradings of hides that have been infested with ticks as No. 4 quality. The same hide, if free from tick marks, would grade No. 2. The difference in price between these two grades of hides is 3 cents a pound. As the hide of a southern steer weighs about 42 pounds, the presence of the tick in the hide causes a loss in the hide alone of more than $1.26 a hide. It has been shown that the cost of tick eradication is only about 50 cents a head, so that if the counties make a systematic campaign to eradicate the tick, the increase in value of the hide alone would pay for the cost of tick eradication and leave the farmer a net profit of about 76 cents a hide.

The shrinkage in the milk production of cattle harboring many ticks will average 1 quart a day, which in the aggregate is a heavy loss. The damage resulting to the southern purchaser of northern purebred or high-grade cattle is another item of no small moment. About 10 per cent of all such cattle taken into the South die of Texas fever, even after they are immunized by blood inoculations, and about 60 per cent of them succumb to Texas fever when not so treated. As they are usually very expensive animals and of a highly valued strain of blood, the loss in certain cases is excessive and in others almost irreparable, owing to the possible extinction of some particular type especially selected for the improvement of the herd.

Another instance in which it is difficult to figure the injury done by the ticks is in the case of death of nonimmune cattle in the tick-free pastures of the South. Such animals are as susceptible to Texas fever as nonimmune northern cattle, and inasmuch as there is in many States only one out of every four farms infested with ticks, the cattle on the remaining farms will in many cases contract Texas fever when exposed to the fever tick. These losses can scarcely be computed, as the death rate depends so much on the season of the year when exposure occurs and on the age of the animal affected. However, the deaths among such cattle are considerable, although this fact is little appreciated or understood by many outside the infected area.

On rare occasions a small outbreak of Texas fever occurs north of the quarantine line as a result of improperly disinfected cars, of unscrupulous dealers breaking the quarantine regulations, or of some accidental condition. Such damage, however, is slight, but should be considered in summing up the loss occasioned by the fever tick.

The advertisement which a breeder obtains and the sales which are made by having his stock in the show ring are usually lost to the cattle raiser in the infected area who aspires to display his animals in the North, as they are barred from most of these exhibitions. On the other hand, the southern farmer is not given an opportunity to see and be stimulated by the fine specimens of northern cattle which might be shown at southern stock exhibits, for the reason that the danger of contracting Texas fever is too patent to warrant such exposure. A heavy expense is incurred by the Government and the States in enforcing the regulations that apply to the quarantine line.

Another loss which is indirectly sustained by the southern cattle industry through increased freight rates is the cost, to the railroad companies, of cleaning and disinfecting the cars that carry cattle and in providing separate pens for them at various places.

These statements are sufficient to indicate that the loss to the quarantined section from the cattle tick is something enormous. Such a series of encumbrances as those recorded could be carried by the cattle industry of no other section of the country than the South, whose excellent pastures, rich soil, and salubrious climate are the only reasons for its ability to overcome such obstacles in meeting the competition of the West; and it is the inherent capacity of the South for greatly increasing its herds and enlarging its pasture lands that makes the actual loss even secondary to the potential loss from restrictions necessitated by the presence of the cattle tick. This potential loss may be described as the difference between the value of the cattle industry of the South to-day and the extent to which this industry would be increased if farmers and ranchmen were assured that their lands and cattle would not become infested with fever ticks. Could this assurance be given, the beneficial effects would extend over the entire country, because the market of the northern breeder would thereby become greatly extended.

These appalling losses and annual sacrifices of the cattle raisers of the infected district can be entirely effaced, and this at a small proportionate cost; for, with enthusiastic stockmen, satisfactory State legislation, sufficient money, and a corps of trained inspectors, the cattle tick may be exterminated, and every dollar expended in this work will be returned many times during each succeeding year.

The so-called period of incubation.—After the young ticks have attached themselves to cattle the fever appears about 10 days thereafter in midsummer. When the weather is cool, as in autumn, this period may be a little longer. The actual period of incubation may be shorter, for if blood from a case of Texas fever is injected into the blood vessels of healthy cattle the fever may appear within five days. When cattle graze upon pastures over which southern cattle have passed, the time when the disease appears varies within wide limits. When the animals have been put upon pastures immediately after southern cattle have infected them with ticks, it may take from 30 to 60 days, or even longer, before the disease appears. This will be readily understood when we recall the life history of ticks. The southern cattle leave only matured ticks which have dropped from them. These must lay their eggs and the latter must be hatched before any ticks can get upon native cattle. The shortest period is thus not less than 30 days if we include 10 days for the period of incubation after the young ticks have attached themselves to native cattle. When the infection of pastures with ticks has taken place early in the season, or when it is cold, the period is much longer, because it takes longer for the eggs to hatch.

If native cattle are placed upon pastures which have been infected with ticks some time before, the disease will appear so much sooner, because the young ticks may be already hatched and attack the cattle at once. It will be evident, therefore, that the length of time between the exposure of native cattle on infected fields and the appearance of the disease depends on the date of original infection, and on the weather, whether cold or hot. When native cattle are placed upon fields on which young ticks are already present, they will show the fever in 13 to 15 days if the season is hot.

The fever appears before the ticks have matured. In fact, they are still small enough to be overlooked. In any case very careful search should be made for them in those places which they prefer—the thighs, escutcheon, and udder. After the acute stage of the fever has passed the ticks begin to swell up and show very plainly. (Pl. XLVI, figs. 6 and 7.)

Prevention.—It is generally accepted that if southern cattle are entirely free from that species of tick known as Margaropus annulatus they can be allowed to mingle with the most susceptible animals without danger. Furthermore, it has been learned from the study of the life history of the cattle tick and by observation that this tick infests pastures only transiently, never permanently, and will not mature except upon cattle or equines, that its extermination is possible, and that the disease it causes may be prevented. Therefore the various methods with these results in view should be directed toward the destruction of ticks on cattle as well as their eradication from the pastures.

METHODS OF ERADICATING THE TICKS.[7]

In undertaking measures for eradicating the tick it is evident that the pest may be attacked in two locations, namely, on the pasture and on the cattle.

In freeing pastures the method followed may be either a direct or an indirect one. The former consists in excluding all cattle, horses, and mules from pastures until all the ticks have died from starvation. The latter consists in permitting the cattle and other animals to continue on the infested pasture and treating them at regular intervals with agents destructive to ticks and thus preventing engorged females from dropping and reinfesting the pasture. The larvae on the pasture, or those which hatch from eggs laid by females already there, will all eventually meet death. Such of these as get upon the cattle from time to time will be destroyed by the treatment, while those which fail to find a host will starve in the pasture.

Animals may be freed of ticks in two ways. They may be treated with an agent that will destroy all the ticks present, or they may be rotated at proper intervals on tick-free fields until all the ticks have dropped. The method most generally used is dipping the cattle in a solution of arsenic. The pasture-rotation method is not only more complicated, but the necessary tick-free fields are seldom available.

DIPPING.

The dipping vat is the best and cheapest means of applying the tick-destroying solution. The great advantage of dipping over spraying and applying remedies by hand lies in the fact that thoroughness of the treatment is practically assured.

When eradication is undertaken, all the cattle, and also the horses and mules if they harbor ticks, are treated regularly every two weeks during the part of the year that the temperature is favorable to treatment, until the ticks have disappeared. The purpose of the treatment is to destroy all ticks that get on the animals before they have had a chance to mature and drop, thus preventing them from reinfesting the pasture, farm, or range. If the treatment used were absolutely effective in destroying each and every tick on the animals treated there would be no renewal of the infestation after the treatment is begun. The cattle would act simply as collectors of ticks which would be destroyed regularly by the treatment applied every two weeks. It is probable, however, that in most instances, either because of the lack of efficiency of the dip or imperfect application, or because of failure to dip all cattle systematically, some ticks escape treatment and reproduce, thus prolonging the time that otherwise would be required for eradication.

If ticks apparently disappear from the cattle after they have been under treatment for some time, the dipping should not be discontinued until a number of careful inspections show that the cattle are free of ticks. If ticks continue on cattle until cold weather and then finally disappear it should be borne in mind that in all probability eradication has not been accomplished and that there may be engorged females, unhatched eggs, and inactive seed ticks on the farm or range, and that even if the cattle should remain free of ticks during the winter they may become reinfested the following spring. In any case in which ticks disappear from the cattle and treatment is discontinued, the cattle should be watched very carefully for ticks until ample time has elapsed to leave no doubt that eradication has been accomplished.

As a general rule it has been found that if dipping is begun in March and systematically and thoroughly done, all cattle being dipped every 14 days until November, complete eradication will be secured. In dipping, each animal should be completely covered by the dip. To prevent any animals from going through the vat without becoming wet all over, a man, provided with a forked stick, should be stationed at the middle of the vat to shove under those that have not been completely submerged.

Dipping is the only really satisfactory method of treating animals for ticks. In cases of emergency, however, or where there are not cattle enough within a radius of several miles to warrant the construction of a vat in which all the cattle of the community may be dipped, spraying may be advisable. In spraying animals the work should be done with great thoroughness and every portion of the body treated. An animal can not be sprayed properly unless it is tied or otherwise held, nor can good results be obtained unless the hair and skin are thoroughly wetted.

Preparation and use of arsenical dips.[8]—After experimenting for many years to discover a practical method for dipping cattle to destroy ticks without injury to the cattle, the Bureau of Animal Industry has developed a very satisfactory arsenical dip. Two formulas are given for homemade dips, one known as the "S-B" (self-boiled) and the other as the boiled dip. The former is the one usually employed.

The S-B dip.—The formula calls for two stock solutions, arsenic stock and tar stock, which must not be mixed except in the diluted dipping bath.

Arsenic stock requires the following materials ready to hand before starting: Pounds. Caustic soda 4 White arsenic 10 Sal-soda crystals 10

There should be also some means for heating the solution in case, as sometimes happens because of impure materials, lack of skill, or some unforeseen circumstance, the heat created by mixing the materials should be insufficient to dissolve all the arsenic.

In a 5-gallon kettle or metal[9] pail place the 4 pounds of caustic soda, add 1 gallon of cold water, and stir with a stick until the caustic soda is practically all dissolved. Without delay begin adding the white arsenic, in portions of a pound or two at a time, as fast as it can be dissolved without causing the solution to boil, stirring all the time. If the liquid begins to boil, stop stirring and let it cool slightly before adding more arsenic. The secret of success is to work the arsenic in fast enough to keep the solution very hot—nearly but not quite at the boiling point. The result should be a clear solution, except for dirt. If the liquid persistently remains muddy or milky, it may be because the operation has been conducted so fast that much water has been boiled out and sodium arsenite is beginning to crystallize, so add another gallon of water and stir. If the solution does not then clear up, the caustic soda must have been very low grade, and the undissolved substance must be arsenic. In that case, put the kettle over the fire, heat nearly, but not quite, to boiling, and stir. As soon as the solution of arsenic is complete, dilute to about 4 gallons, add the sodium carbonate, and stir until dissolved.

Cautions.—It is necessary to avoid splashing. Hence never work hurriedly; stir deliberately and regularly; do not dump in the arsenic and sal soda, but carefully slide them in from a grocer's scoop held close to the side of the pail and to the surface of the liquid. Perform the whole operation in a well-ventilated place and avoid inhaling steam.

After the solution has become cold add water to make it to exactly 5 gallons,[10] mix well, let settle, and draw off into containers which can be tightly corked or otherwise closed. Jugs or demijohns are best, but tin cans will serve if occasionally inspected for leaks which may occur after a time through the action of the solution upon the solder of the can.

Tar stock is prepared thus: In a large metal pail dissolve three-fourths of a pound of caustic soda in 1 quart of water, add 1 gallon of pine tar, and stir thoroughly with a wooden paddle until the mixture, which at first looks streaked and muddy, brightens to a uniform, thick fluid somewhat resembling molasses. Test it by letting about a teaspoonful drip from the paddle into a glass of water (a glass fruit jar or a wide-mouth bottle will do) and stirring thoroughly with a sliver of wood. It should mix perfectly with the water. Globules of tar which can be seen by looking at the glass from underneath and which can not be blended with the water by repeated stirring indicate that more caustic-soda solution is needed. In that case make up more caustic-soda solution of the same strength and add it, not more than a pint at a time, with thorough stirring, until the desired effect is produced.

If an appropriate glass vessel for making the test is not at hand, take a little of the mixture between the fingers, then dip the fingers under water and try to rub off the tar. It should leave the fingers perfectly clean after a little rubbing with water. If an oily coating remains, more caustic-soda solution is needed. Such an extra addition of caustic soda will be required only in case of a very low-grade chemical or a very highly acid tar. The tar stock should be kept in closed containers, such as a pail with a friction top.

The quantity of S-B arsenic stock or of tar stock made in one operation can be varied as desired, provided the above-given proportions of the ingredients are adhered to. But one should attempt to work the S-B formula on a larger scale only after skill and experience have been acquired.

The boiled dip is less convenient than the S-B dip, but the final composition and effect of dipping baths prepared from the two are the same.

To make a 500-gallon bath provide:

Sal-soda crystals 24 pounds. White arsenic 8 pounds. Pine tar 1 gallon.

Put 25 gallons of water into a kettle or tank of from 40 to 50 gallons' capacity, heat to boiling, and add the sal soda. When this has dissolved add the white arsenic, then boil and stir for 15 minutes or longer, until the white arsenic has entirely disappeared. If intended for immediate use cool to 140 deg. F. (by addition of cold water if desired), then pour in the pine tar in a thin stream while constantly and vigorously stirring the solution. Immediately empty the liquid into the dipping vat, which has already been three-fourths filled with water, and stir thoroughly.

All the utensils must be free from greasy or oily matter which would coat the arsenic and hinder its solution. The operation of boiling requires constant attention to avoid loss by foaming. Hard water may be used, but in that case considerable undissolved material, which, however, does not contain any arsenic, may be left after boiling.

For a stock solution to be kept on hand and used when needed add no tar, but after the solution has become cold make it up to 25 gallons, stir well, let settle, and draw off into containers which can be well closed. In this case the tar stock previously described is also required.

Diluting the dip.—First run water into the vat about three-fourths up to the dipping line, at which its capacity must be known. If tar stock is to be used the necessary amount will be one-third of a gallon for every 100 gallons of vat capacity. Measure it out, mix it with 2 or 3 times its volume of water and pour it along the surface of the water in the vat, stirring a little.

Every 100 gallons of standard-strength bath calls for 1-3/5 pounds white arsenic, which quantity is contained in four-fifths of a gallon of S-B stock or in 5 gallons of boiled stock. From these figures the quantity of arsenic or stock needed to charge the vat may be calculated. Or one may base the calculation on the following facts:

One pound of white arsenic will make 62-1/2 gallons of bath. One gallon of S-B stock will make 125 gallons of bath. One gallon of boiled arsenic stock will make 20 gallons of bath.

All solutions of arsenic are considerably heavier than water and if carelessly put into the vat they may plunge to the bottom and be difficult to mix. Therefore always pour the arsenic stock or a proprietary dip in a thin stream evenly along the vat except at the shallow exit end. Another precaution to be taken in handling proprietary dips is never to mix them first with small quantities of water, which may "break" them. Pour them directly into the water in the vat.

Finally, add water up to the dipping line and stir well. An excellent way to stir is by a pail tied to a rope. Sink it at the entrance end of the vat and haul it along the bottom to the exit. Then raise it, throw it back to the entrance end, and haul through again, repeating as many times as necessary but always hauling through in the same direction.

The standard-strength bath prepared as above contains practically 0.19 per cent arsenious oxid when fresh. After use oxidation may set in and weaken it, but it will not need to be strengthened so long as it tests not less than 0.175 per cent arsenious oxid.

To make up small quantities for spraying, to each 5 gallons of water measured out add first 2 fluid ounces (4 tablespoonfuls) of tar stock, and then 5-1/8 fluid ounces of S-B stock or 2-1/8 pints of boiled arsenic stock.

The standard strength of bath should be adhered to so far as possible because its effectiveness against ticks will effect eradication in the least time and with fewest dippings. But if time is not pressing it is sometimes best to begin with a lower strength, say 0.14 or 0.15 per cent, and gradually work up to full strength as the cattle become accustomed to the treatment. This is certainly a wise method for the individual cattle owner who is outside the area of cooperative work and who lacks aid and advice from experts. Weather conditions also need to be considered. Hot or moist weather is more trying to the cattle than cool or dry weather. The longer the time needed for the cattle to dry off after dipping, which of course primarily depends on the proportion of moisture in the air, the more liable they are to show blistering or other injury through the continued absorption of arsenic by the skin. The combination of heat and moisture is particularly bad, and under such conditions it may be desirable, unless other conditions prohibit, to use the bath somewhat weaker than standard strength. The following table shows the quantities of arsenic and stock solutions contained in 100 gallons of bath of different strengths, so that the quantities necessary to charge a vat of any size at any strength can be found by simple multiplication.

Composition of dipping baths.

+ -+ + Actual Per 100 gallons of bath. arsenious + + oxid. White S-B Boiled arsenic. stock. stock. + -+ + -+ -+ Per cent. Pounds. Gallons. Gallons. 0.05 0.42 0.21 1.3 .06 .50 .25 1.6 .07 .58 .29 1.8 .08 .66 .33 2.1 .09 .75 .38 2.3 .10 .83 .42 2.6 .11 .91 .46 2.8 .12 1.00 .50 3.1 .13 1.08 .54 3.4 .14 1.16 .58 3.6 .15 1.25 .63 3.9 .16 1.33 .67 4.2 .17 1.41 .71 4.4 .18 1.49 .75 4.7 .19 1.58 .79 4.9 .20 1.66 .83 ... .21 1.74 .87 ... .22 1.83 .92 ... .23 1.91 .96 ... .24 2.00 1.00 ... + -+ + -+ -+

As dipping goes on the bath naturally needs replenishing, and its strength probably needs correction from time to time. Full directions on these points may be found in Farmers' Bulletin 1057.

Prepared dips.—Proprietary arsenical cattle dips appear now to have passed the experimental stage and to have become established as reliable and useful products. At any rate this can be said of the brands which have received permission for use in official dipping in place of the homemade dip. The formulas and standard samples of all such brands are in possession of the Bureau of Animal Industry and the manufacturers are required to guarantee that their products as placed on the market will be kept up to standard and that all requirements of the bureau will be observed. Like the homemade dip they all contain sodium arsenite as the active tick-killing agent. They do not all contain pine tar, because that substance is difficult to blend into a highly concentrated product, but they all contain some other substance or mixture of substances of such character and in such quantity as field trials have proved will produce the same effects.

They are not regarded as any more effective or any milder on the cattle than properly prepared homemade dips. None the less they are undoubtedly safer for general use because they offer decidedly fewer opportunities for making mistakes in the quantities used or in the operations gone through and also fewer chances for accidental poisoning or other injury from the handling of powerful chemicals. Whether their higher cost is sufficiently outweighed by these considerations is necessarily a matter for individual decision.

Precautions in the use of arsenic and arsenical dips.—The fact that arsenic is a violent poison is what renders it valuable, for the fever tick is hard to kill. But, like a keen-edged tool, it may be decidedly dangerous if ignorantly or carelessly handled. Three possibilities of danger must be kept constantly in mind; danger to oneself, danger to other persons, danger to animals.

The dry, powdered white arsenic should be kept in a tightly covered pail, plainly labeled. Paper bags are unsafe because they easily burst, and arsenic so scattered about looks harmless enough. In weighing or otherwise handling the arsenic avoid raising dust or breathing it in, if raised, and keep it off the skin and clothing. In mixing or boiling stock solutions work only in a well-ventilated place, and on the windward side of the kettle so that steam arising from it will not be inhaled.

The stock solutions are in some respects more dangerous than the original substance because the arsenic in them is already in solution and can act very quickly. If any gets on the skin or clothing it must be washed off without delay. Cattle must be kept away from such solutions or from anything that has been in contact with them, for cattle craving salt have been poisoned by licking the outside of leaky barrels and by licking the earth around dipping vats where a little concentrate had been carelessly spilled in charging the vat. All such poisoned earth must be removed, buried, and replaced by fresh.

The diluted bath is naturally much less dangerous, but no chances can be taken with it. No puddles from which animals may drink should be allowed to accumulate. The persons who do the dipping should not allow the skin or clothing to be wet by the dip any more or any longer than absolutely necessary. When spraying, the operator should see to it that neither he nor the animals inhale any of the spray.

When a vat is to be emptied the approved practice is to run the waste bath into a pit properly guarded by a fence, where it will gradually seep away under the surface and do no harm, provided only that seepage can not be carried to a well, stream, or spring from which any person or domestic animal may drink.

The symptoms of arsenical poisoning are rather variable and also depend on the size of the dose and the method of administration. If an animal sickens or dies shortly after dipping it by no means follows that arsenical poisoning or any other effect of the dipping is the cause. Very few cattle relative to the total number dipped have suffered undoubted arsenical poisoning and in most of the cases the cause could be traced to somebody's error or carelessness.

In regard to arsenical poisoning of human beings there is a standard antidote, which may be obtained at any drug store with directions for use. It should be kept on hand for emergencies. If the antidote is not at hand the poison must be removed from the stomach by encouraging repeated vomiting, and soothing drinks such as milk, white of eggs and water, or flour and water must be freely given meanwhile. A suspected case of arsenical poisoning must have the attention of a physician at the earliest possible moment, as sometimes the poison works very quickly.

Crude petroleum.—Various kinds of crude petroleum and emulsions of it have been used with more or less success in destroying ticks, but on account of the difficulty of obtaining suitable grades of oil and the liability of injury to cattle, their use has been practically abandoned.

Method of dipping.—The method usually adopted in dipping cattle is to construct a narrow swimming tank with a chute at one end for the entrance of the cattle, and a sloping exit at the other end when the cattle emerge after passing through the vat. (See Pl. XLIX, fig. 2.) A drip chute, or floor, is connected with the exit, where the excess of dip is allowed to drip off the animals and to drain into the vat. Plans and specifications for installing dipping plants may be obtained from the Bureau of Animal Industry, Department of Agriculture, Washington, D. C.

TREATMENT.

When Texas fever has broken out, all animals, the sick as well as the healthy, should at once be removed to a noninfected pasture. While this may not cut short the disease, it may save the lives of some by removing them from the possibility of attack by more young ticks. Removal from infected pastures likewise prevents a second attack, in October or early in November, which is caused by another generation of ticks. Sick native cattle infect with a new generation of ticks the pasture to which they are removed, but these usually appear so late that they have but little opportunity to do any damage; hence, sick natives do not, as a rule, cause visible disease in other natives.

It is of importance to remove all ticks, so far as this is possible, from sick animals, since they abstract a considerable quantity of blood and thereby retard the final recovery.

Medical treatment of the sick has generally been unsatisfactory, although in chronic cases and those occurring late in the fall beneficial results have followed. If the animal is constipated, a drench containing 1 pound of Epsom salt dissolved in 1 quart of water should be administered, followed by sulphate of quinin in doses of 30 to 90 grains, according to the size of the animal, four times a day until the system is well saturated with it. Tincture of digitalis one-half ounce and alcohol 2 ounces may be combined with the quinin, according to indications of individual cases. An iron tonic containing reduced iron 2 ounces, powdered gentian 4 ounces, powdered nux vomica 2 ounces, powdered rhubarb 2 ounces, and potassium nitrate 6 ounces will be found beneficial in the convalescent stage when the fever has run its course. This tonic should be given in heaping teaspoonful doses three times a day in the feed. Good nursing is essential in treating these cases, and the animal should be given a nutritious, laxative diet with plenty of clean and cool drinking water and allowed to rest in a quiet place. If the stable or pasture is infested with ticks, the animal should be placed in a tick-free inclosure to prevent additional infestation with these parasites and the introduction of fresh infection into the blood. Furthermore, all ticks that can be seen should be removed from the sick cattle, as they keep weakening the animal by withdrawing a considerable quantity of blood, and thereby retard recovery.

QUARANTINE REGULATIONS.

The sanitary regulations issued by the Department of Agriculture for the control of cattle shipments from the infected districts have for their initial purpose the prevention of the transportation of ticks from infected regions to those that are not infected, either upon cattle or in stock cars or other conveyer. They are based upon the fact that Texas fever is carried north only by the cattle tick, and the exclusion of this parasite from the noninfected territory has in every instance been found a certain method of excluding Texas fever. The regulations governing the movement of cattle from below the quarantine line are made yearly by the Secretary of Agriculture, and they define the boundary of infected districts. The infected area as now determined is shown in maps issued periodically.

In consequence of the enforcement of these quarantine regulations, Texas fever has been practically prevented in the noninfected districts for several years, and little or no hardship has been caused to stockmen handling cattle from the infected areas. Prior to the adoption of these regulations the tick-infested district was rapidly extending northward, but since the quarantine line was established and rational regulations enforced it has gradually been moved farther south. This problem of still further reducing the infested area is of the greatest importance to the cattlemen of the South—in fact, to those on both sides of the line—and one which is receiving special consideration by this department as well as by many of the interested States.

TICK ERADICATION.

Systematic cooperative work by the Federal Government and the affected States for the eradication of the cattle ticks which transmit Texas fever was begun in the summer of 1906 under authority given by Congress in the appropriation act for the Department of Agriculture. The first Federal appropriation for the fiscal year ended June 30, 1907, was $82,500, and for the fiscal year 1908 an appropriation of $150,000 was made, then for several years $250,000, and this has been increased to $660,000 for 1922. Funds have also been provided by States and counties.

The original infected area amounted to 728,543 square miles. Of this territory there has been released from quarantine as a result of the work above mentioned 523,837 square miles (up to July 1, 1922). In other words, 72 per cent of the area has been freed from ticks in 16 years.

Great improvement has resulted from this work in the released territory. More cattle are being raised, and a better grade of breeding stock is being introduced; calves grow faster, and cattle put on flesh more rapidly during the grazing season and go into the winter in better condition because of the absence of the ticks; they can be marketed without quarantine restrictions, and higher prices are being obtained; dairy cows give a larger yield of milk; and values of farm lands are enhanced.

The difference between the prices realized for cattle from the tick-infested region and the prices of cattle of similar grades from above the quarantine line has ranged from $2.25 to $5 a head at the principal northern live-stock markets, without taking into account the improvement in quality and weight of cattle because of the eradication of the ticks. It can easily be seen that the extermination of the ticks means a large total annual increase in the prices obtained for southern cattle sold in northern markets. In addition to this, the increase in prices of cattle sold locally in the South would represent a large sum. This local increase has been found to amount to from $3 to $15 a head in territory freed from ticks. An agricultural official of one of the Southern States has reported that calves in the tick-free area bring double the prices that can be obtained for similar calves in the tick-infested region.

Heretofore it has been impracticable to improve the quality of southern cattle by introducing fine breeding animals from other sections, because such animals were liable to contract Texas fever and die unless protected by inoculation. Furthermore, it is impossible for animals to attain good growth and to thrive when they are heavily infested with ticks. With the eradication of the ticks, however, the southern farmers are enabled to introduce good breeding animals and to improve the grade of their stock.

There is no longer any doubt that it is entirely practicable to exterminate the ticks throughout the entire region, and the accomplishment of this result will be of tremendous economic advantage not only to the South but to the whole country. The rate of progress depends mainly on two factors— the amounts appropriated by the Federal and State Governments, and the cooperation of the people.

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SOUTHERN CATTLE FEVER (TEXAS FEVER, TICK FEVER). DESCRIPTION OF PLATES.

PLATE XLIV. Normal spleen and spleen affected by Texas fever.

Fig. 1. Spleen of an acute, fatal case of Texas fever. The narrow end of the spleen is here represented.

Fig. 2. Spleen of healthy steer. Though the latter animal weighed one-half more than the former, the weight of the diseased spleen (6-7/8 pounds) was nearly three times that of the healthy spleen (2-3/8 pounds).

PLATE XLV. Texas fever.

Fig. 1. The cut surface of a healthy liver taken from a steer slaughtered for beef.

Fig. 2. The cut surface of the liver in Texas fever.

Fig. 3. Appearance of the urine in an acute, fatal case of Texas fever.

Fig. 4. Red corpuscles, magnified 1,000 diameters, containing the parasite of Texas fever. This appears as a blue point a near the edge of the corpuscle. The blood was taken from a skin incision. The case was nonfatal and occurred late in the fall.

Fig. 5. Red corpuscles from the blood of an acute, fatal case, 20 hours before death. The Texas-fever microbes a are shown as pear-shaped bodies, stained with methylene blue, within the red corpuscles. The larger body on the right b is a white blood corpuscle, also stained with methylene blue. (Magnified 1,000 diameters.)

PLATE XLVI. The cattle tick (Margaropus annulatus), the carrier of Texas fever.

Fig. 1. A series of ticks, natural size, from the smallest, just hatched from the egg, to the mature female, ready to drop off and lay eggs.

Fig. 2. Eggs, magnified 5 times.

Fig. 3. The young tick just hatched (magnified 40 times).

Fig. 4. The male after the last molt (magnified 10 times).

Fig. 5. The female after the last molt (magnified 10 times).

Fig. 6. A portion of the skin of the udder, showing the small ticks. From a fatal case of Texas fever produced by placing young ticks on the animal. (Natural size.)

Fig. 7. A portion of the ear of the same animal, showing same full-grown ticks ready to drop off. (Natural size.)

PLATE XLVII. The cattle tick (Margaropus annulatus).

Fig. 1. Dorsal view of male. (Greatly enlarged. Original.)

Fig. 2. Ventral view of male. (Greatly enlarged. Original.)

Fig. 3. Dorsal view of replete female. (Greatly enlarged. Original.)

Fig. 4. Ventral view of same.

PLATE XLVIII. Portion of a steer's hide, showing the Texas-fever tick (Margaropus annulatus). (Natural size. Original.)

PLATE XLIX. Fig. 1. Tick-infested steer.

Fig. 2. Dipping cattle to kill ticks.

PLATE L. Facsimile of poster used to show the difference between cattle of similar breeding raised on a tick-free farm in one case and on a ticky farm in the other.

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CHRONIC BACTERIAL DYSENTERY.

Chronic bacterial dysentery is a chronic infectious disease of bovines caused by an acid-fast bacillus simulating the tubercle bacillus and characterized by marked diarrhea, anemia, and emaciation, terminating in death.

This disease was observed in the United States for the first time by Pearson in Pennsylvania cattle, and later by Mohler in Virginia cattle, and in an imported heifer from the island of Jersey at the Athenia quarantine station of the Bureau of Animal Industry.

Pearson proposed the name chronic bacterial dysentery for this affection, and it has also been termed Johne's disease, chronic bacterial enteritis, chronic hypertrophic enteritis, and chronic bovine pseudotuberculous enteritis by various European investigators. The disease was first studied in 1895 by Johne and Frothingham in Dresden, but they were inclined to attribute to the avian tubercle bacillus the cause of the peculiar lesions of enteritis which they observed. In 1904 Markus reported this disease in Holland, and subsequently it was observed in Belgium, Switzerland, Denmark, and Great Britain.

Cause.—The bacillus, which has been invariably demonstrated in the intestinal lesions and mesenteric lymph glands in this disease, is a rod about 2 to 3 microns long and 0.5 micron wide. It stains more or less irregularly, like the tubercle bacillus, and moreover the similarity goes further, in that the organism is also strongly acid-fast, which facts led Johne and Frothingham to surmise that the disease was caused by avian tubercle bacilli. However, it has now been plainly demonstrated that the bacillus of chronic bacterial dysentery is readily distinguished from the latter organisms, for while it resembles the tubercle bacillus in form and staining qualities, no one has succeeded in growing it in culture media or in reproducing the disease by injecting experiment animals.

Symptoms.—Probably the first symptom noticed is that the animal is losing condition despite the fact that its appetite is good and the food nourishing. This is soon followed by a diarrhea which, while moderate at first, soon becomes excessive and may be either irregular or persistent, the feces being of the consistency of molasses and passed frequently. In the meantime the hair becomes dry and harsh and the animal falls off considerably in weight. The temperature, however, remains about normal. The appetite does not seem to be greatly impaired until the last few weeks of life, but nevertheless emaciation continues, the animal becomes more and more anemic, great muscular weakness and exhaustion are manifested, and death follows, apparently as the result of the persistent diarrhea and great emaciation. The disease may continue for four or five weeks or may last for a year, or even longer, before death intervenes.

Lesions.—The lesions observed on post-mortem are remarkably slight and are out of all proportion to the severity of the symptoms manifested. The disease appears to start in the small intestines, especially in the lower portion, where the lesions are usually the most marked, but it also involves the large intestines, including the rectum. The mucous membrane may alone be affected, although usually in the long-standing cases the submucosa is also invaded and the entire intestinal wall is then much thicker than normal and the tissue infiltrated with an inflammatory exudate. The mucous membrane or inside lining membrane is markedly wrinkled or corrugated, showing large, coarse folds with more or less reddening or hemorrhagic patches or spots on the summits of the ridges, especially noticeable in the large intestines. The mesenteric lymph glands are usually somewhat enlarged and appear watery on section. The other organs do not appear to be affected except from the anemia present in the later stages of the disease.

Differential diagnosis.—The principal disease with which bacterial dysentery may be confused is tuberculosis, but the application of the tuberculin test will readily diagnose the latter disease, while no reaction will be noted in case the injected animal is suffering with the former affection. The disease may also be mistaken for the parasitic affections resulting from stomach worms (verminous gastritis) and intestinal parasites, especially uncinariasis, but a microscopic examination of the feces is necessary in order to establish definitely the diagnosis.

Treatment.—As with all other forms of infectious disease, it is advisable to separate immediately the diseased and suspected cattle from the healthy animals. The feces passed by the former animals should be placed on cultivated soil where healthy cattle will not be exposed to them, as the bacilli producing the disease are readily found in such manure. The stalls, stables, and barnyards should also be thoroughly disinfected, as has been described under "Tuberculosis," in this chapter, special attention being given to those places which have been soiled by feces. The administration of medicines has thus far been quite unsatisfactory, although treatment should be directed toward disinfecting the intestines with intestinal antiseptics, such as tannopin in 1 dram doses twice daily, and strengthening the animal by the use of stimulants such as strychnin in half-grain doses given twice daily hypodermically. Salol, turpentine, or subnitrate of bismuth in a starch or wheat-flour gruel may also give temporary relief, but the diarrhea is likely to reappear and cause the death of the animal. In all cases the feed must be carefully selected to assure good quality, and should consist preferably of nutritious dry feed.

NAGANA.

Nagana, also called tsetse-fly disease, is an infectious fever occurring chiefly in horses and cattle, characterized by alternating paroxysms and intermissions and produced by a specific flagellate protozoan (Trypanosoma brucei) in the blood. It is probably transmitted from animal to animal solely by the bites of the tsetse fly. This insect is something like a large house fly, and when it settles on a diseased animal, sucks the blood and infects its proboscis, it is enabled on biting a second animal to infect the latter by direct inoculation. This disease is found throughout a large portion of central and southern Africa, along the low-lying and swampy valleys. It has never occurred in the United States, nor is it known to be present in the Philippines, but its relation to surra and the possibility of its appearance in one of our island dependencies are the reasons for including a few remarks at this time.

Symptoms.—The chief symptoms in addition to the fever, which is usually about 104 deg. to 105 deg. F., are the muscular wasting, progressive anemia, and loss of power, together with the edema most marked about the head, legs, abdomen, and genital organs. The urine is yellow and turbid, and occasionally contains albumin and blood. There is paralysis of one or both of the hind legs, difficult urination and defecation, labored breathing, discharge from the eyes and nose, extreme thirst, and gradual extension of paralysis to other parts of the body. The disease runs a chronic course, lasting from three to six weeks in horses, and from one to six months in cattle. Besides these animals, the mule, ass, buffalo, antelope, hyena, camel, and dog contract the disease naturally, and sheep, goats, cats, and small laboratory animals succumb to artificial inoculation.

Lesions.—The spleen and lymphatic glands are enlarged. There are sero-fibrinous exudates in the body cavities, the liver is enlarged and engorged, heart flabby, and a catarrhal condition is present in the respiratory passages. Pathological changes occur in the spinal cord. The finding of the trypanosoma by microscopic examination of the blood will be conclusive evidence for diagnosis.

Treatment.—Treatment has not proved satisfactory. Quinin, arsenic, methylene blue, and other drugs have been used, but without success. Endeavors thus far made to produce immunity from this disease have likewise been unavailing.

CATTLE FARCY.

This is a chronic disease of cattle occurring in France and the island of Guadeloupe, West Indies. It is characterized by caseating nodular swellings, first of the skin and afterwards of the superficial lymphatic vessels and glands, finally proving fatal within a year by extension to the viscera. The swellings rupture and discharge a purulent yellowish fluid, which contains the causative organism. This affection, called farcin du boeuf by the French, resembles cutaneous glanders or farcy of horses, but is caused by an entirely different organism, the streptothrix of Nocard. Moreover, cattle are immune from glanders, and for this reason the name, unfortunately applied to this disease, should not lead to any confusion with the cutaneous glanders or farcy of horses. Although the disease has been described as occurring only in Guadeloupe and France, the possibility of its occurrence in American possessions warrants its mention in this chapter.

Treatment.—Treatment consists in making incisions into the swellings and syringing them out with 2 per cent compound cresol solution. The cavities may then be packed with cotton, soaked in 5 per cent zinc-chlorid solution. The swollen lymphatics may also be bathed or covered with cloths wrung out in this solution.

OTHER INFECTIOUS DISEASES.

The following are also infectious diseases of cattle, a discussion of which will be found in previous chapters: Page. Contagious abortion 167 White scour of calves 261 Infectious ophthalmia (pink eye) 345

FOOTNOTES:

[4] These membranes comprise the smooth, very delicate, glistening lining of the large body cavities. In the thorax the serous membrane (pleura) covers the ribs and diaphragm as well as the whole lung surface. In the abdomen a similar membrane (peritoneum) lines the interior of the cavity and covers the bowels, liver, spleen, etc.

[5] Hogs are subject to actinomycosis.

[6] The distribution of Government blackleg vaccine was discontinued July 1, 1922.

[7] Only a general outline of methods of eradication will be given here. For detailed information, including directions for the construction of dipping vats and for the preparation of dips, the reader is referred to Farmers' Bulletin 1057, which may be obtained free upon application to the Department of Agriculture, Washington, D. C.

[8] For fuller information see Farmers' Bulletin 1057, from which the directions here given are mainly derived.

[9] The chemicals employed have no effect upon iron. They will, however, actively corrode zinc, tin, or solder; hence a soldered pail must be watched for leaks and is far inferior to a seamless pail, stamped from a single sheet of iron. A tinned pail is preferred to a galvanized one, but a plain iron seamless pail or an iron kettle should be obtained if possible.

[10] Best done by previously determining by measurement the depth of 5 gallons of water in the kettle. Set the kettle exactly level and mark the depth on a stick held vertically on the center of the bottom.



ANIMAL PARASITES OF CATTLE.

By B. H. RANSOM, Ph. D.,

Chief of Zoological Division, Bureau of Animal Industry.

The animal parasites of cattle comprise more than a hundred different species, belonging to various groups of the animal kingdom. Fortunately not all these parasites occur in this country—many are uncommon, and many are comparatively harmless. Some forms, however, occur frequently, and some are of distinct importance to the American stockman on account of the damage for which they are responsible. It is these parasites particularly which will be referred to in the present article, and although some forms are discussed which are rare or apparently of little economic importance, most of the minor and unusual parasites and species not found in this country have been omitted from consideration.

FLIES.[11]

Of the various species of flies which infest cattle some are injurious on account of the annoyance, pain, and loss of blood due to their bites, and sometimes also on account of diseases or parasites which are thus transmitted from the blood of diseased animals to that of healthy cattle, while others, which in the winged adult state do not bite, are injurious because they live parasitic on cattle during their larval stages.

Remedies for flies.[12]—Most remedies used for protecting cattle from the attacks of flies have to be applied frequently, and few, if any, will keep flies away for more than a day or two following their application. The numerous proprietary fly repellents to be found on the market are usually more expensive, and often less efficacious than homemade mixtures.

At the Minnesota experiment station rancid lard 1 pound and kerosene one-half pint, mixed thoroughly until a creamy mass forms, was found to give excellent results as a fly repellent, lasting for two or three days, when rubbed not too thickly with a cloth or with the bare hand over the backs of cows. Mixtures of cottonseed oil and pine tar containing from 10 to 50 per cent of the latter substance were found by investigations in the Bureau of Animal Industry to have a marked repellent action against flies when applied lightly every day. A too free application of tar mixtures and other preparations containing phenols is liable to cause poisoning; hence care should be observed in this regard.

Jensen (1909) recommends the following formula, which is said to protect cows for a week:

Common laundry soap 1 pound. Water 4 gallons. Crude petroleum 1 gallon. Powdered naphthalin 4 ounces.

Cut the soap into thin shavings and dissolve in water by the aid of heat; dissolve the naphthalin in the crude oil, mix the two solutions, put them into an old dasher churn, and mix thoroughly for 15 minutes. The mixture should be applied once or twice a week with a brush. It must be stirred well before being used.

THE STABLE FLY (STOMOXYS CALCITRANS).[13]

This fly very closely resembles the house fly, but, unlike the latter, it is a biting fly. It is common about stables and often enters dwellings, especially in cloudy weather. According to Noe, it is the agent of transmission of a parasitic roundworm of cattle (Setaria labiato-papillosa, see p. 529). This fly has been shown capable of transmitting anthrax from diseased to healthy animals, and under some conditions it may transmit surra, a disease caused by a blood parasite which affects horses, cattle, and other livestock.

The annoyance suffered by cattle and horses from stable flies is much lessened if the stables are darkened.

The screening of doors and windows, however, is preferable, as ventilation is not interfered with as it is in darkening stables. For milk cows coverings made from burlap (double thickness), including trouserlike coverings for the legs, may be used when the flies are very numerous and troublesome. One of the fly repellents mentioned above may be applied to cattle to protect them from stable flies. The Hodge flytrap fitted to the windows of dairy barns is a useful means of destroying stable flies. The United States Bureau of Entomology has found that a mixture of fish oil (1 gallon), oil of pine tar (2 ounces), oil of pennyroyal (2 ounces), and kerosene (1/2 pint) is fairly effective for a short time when applied lightly, but thoroughly, to the portions of animals not covered with blankets. The risk of poisoning with tar mixtures as already mentioned should be borne in mind in using this remedy. Care should be taken to apply it lightly.

The stable fly breeds in moist accumulations of straw, chaff, cow or horse manure, and various fermenting vegetable substances. The debris collecting in and under outdoor feed troughs, and the remains of straw stacks are favorable breeding places for the stable fly. Under the most favorable conditions about three weeks are required for development from the egg to the adult stage.

The proper care of straw and the proper disposal of stable manure are very necessary in the control of stable flies. Straw stacks should be carefully built so as to shed rain, and loose straw or chaff should be scattered or burned. Straw not required for winter feed should be promptly disposed of by burning or scattering and plowing it under. Stable manure should be hauled out and scattered at regular intervals, preferably every three days, and the vicinity of stables should be kept free from accumulations of straw and hay that may become wet and serve as breeding places for the stable fly.

THE HORNFLY (LYPEROSIA IRRITANS).[14]

This fly, now found nearly everywhere in the United States, was introduced into this country from Europe about the year 1885. Hornflies have the habit of clustering about the base of the horn (fig. 2), whence the name by which they are popularly known. They do not damage the horn, and congregate there only to rest.

In view of the general practice of dehorning cattle, the name hornfly is less distinctive than it once was. Moreover, hornflies rest on other parts of the body as well as the horns.

When resting, their wings are held down close to the body (fig. 1); when feeding, their wings are held out nearly at right angles, ready for flight. They puncture the skin and suck blood, usually attacking the upper parts of the body, particularly those which are out of reach of the animal's head or tail. Unlike most flies, they remain on the animal more or less constantly, day and night. Owing probably to the irritation and annoyance caused by these flies, cattle often do not thrive as they should during seasons when the flies are numerous. The hornfly has also been charged with transmitting diseases, such as anthrax.











FIG. 2.—DIPPING CATTLE TO KILL TICKS.]



The fly lays its eggs in freshly dropped cow manure. They hatch in about 24 hours, and the larvae or maggots in four or five days develop to the pupal stage, which lasts a week or 10 days. From the pupal stage the mature fly emerges. The entire process of development from the deposition of the egg to the appearance of the mature fly therefore may be completed in two weeks, or even in a shorter time. To protect cattle from attacks of the hornfly they may be treated with one of the remedies mentioned above (p. 502). Dipping cattle in a vat provided with splashboards set at the proper angle destroys most of the hornflies present on the animals. Unless the splashboards are used all but a few of the flies succeed in escaping as the cattle plunge into the bath and later return to them. Scattering the droppings of cattle with a shovel, or with brush dragged over pastures, in order to insure the rapid drying of the manure and consequent destruction of the larvae, is, when practicable, an efficient means of reducing the number of these flies.





BUFFALO GNATS.

These small flies, also known as black flies, are about one-eighth of an inch long and have a characteristic "humped" back (fig. 3). They breed in running water and appear in swarms during spring and summer, often in enormous numbers, causing great annoyance to stock and human beings, on account of their bites and their entrance into the eyes, nose, mouth, and other openings of the body. Their bites appear to be poisonous, and in seasons especially favorable to the gnats heavy losses of horses and cattle often occur.

Buffalo gnats are more troublesome in bright, sunny weather than when it is cloudy, and animals which have not shed their winter coats suffer more from their attacks than those with smooth coats. Cattle kept in darkened stables are not molested. The application of one of the fly repellents already mentioned (p. 502) may help to protect animals from buffalo gnats. The burning of smudges is also a useful means of protecting stock from the attacks of these flies.



SCREW WORMS.[15]

Screw worms (fig. 4) are the maggots of a fly (Chrysomyia macellaria), so called from their fancied resemblance to a screw. The adult fly (fig. 5) is about one-third of an inch long, with a bluish-green body, red eyes, and with three dark longitudinal stripes on the back (thorax). Attracted by odors of decay, it deposits its eggs, 300 to 400 at a time, in cuts, sores, castration wounds, etc. The crushing of a tick on the skin commonly results in screw-worm infection at that point. The eggs hatch in a few hours and the larvae or maggots, or so-called screw worms, begin to burrow into the flesh and continue burrowing and feeding from three to six days, after which they leave the wound and crawl into the earth, there transforming into the quiescent pupal stage. This stage is completed in three to fourteen days. The mature flies then emerge from the pupal envelope and are soon ready for egg laying. From two to three weeks are therefore required for the entire life cycle, although under certain conditions it is possible for the fly to undergo its full development in as short a time as seven days, and on the other hand as long as a month is often required.

Besides cattle, the screw-worm fly attacks sheep, horses, dogs, and man. In the case of hogs it is generally the ears which are affected. The fly also breeds in dead animals, and all carcasses should therefore be buried deeply or burned. The complete destruction of all dead animals by burning has been found by the Bureau of Entomology to be by far the best method of controlling screw worms.

Treatment for screw worms.—For proper treatment an animal suffering from screw worms should be caught and thrown. Chloroform is then poured into the wound, taking care that it penetrates thoroughly into all the burrows of the screw worm, if necessary using a slender stick or a small bunch of twisted hay as a probe. The animal should be held for several minutes in order to insure the continued action of chloroform. Instead of chloroform, gasoline may be used, and carbon tetrachlorid is said by some authorities to give good results. Finally, the dead or dying maggots may be removed with forceps, the wound washed with a weak carbolic or cresylic acid solution, and painted with pine tar to reduce the chances of further attack by flies. Finally the wound should be dressed with a carbolic or cresylic ointment to promote healing and thus prevent further infection, or the wound may be painted with pine tar. Dipping in the arsenical dips used for destroying cattle ticks is a convenient method of treatment if many animals are involved.





GRUBS, WARBLES, BOTS.

Ox warbles are whitish or, when full grown, dark-colored grubs or maggots that develop from the eggs deposited on the hairs of cattle by certain flies known as warble flies. In the United States there are two species of ox-warble flies, technically known as Hypoderma lineatum and Hypoderma bovis. These flies somewhat resemble bees in their general appearance, but like all flies have only two wings.

The first named, H. lineatum, is commonly called the heel fly and is more generally distributed over the United States than the other species. The tail has a distinctive reddish-orange color and the legs are rough and hairy. This fly commonly deposits its eggs about the coronet, whence the name of heel fly, and on the fetlocks, knees, and hocks. When cattle are resting, eggs are deposited along the line of contact of the body with the soil. Cattle are frequently indifferent to the activity of this fly in depositing its eggs. Commonly 8 to 10 eggs, sometimes as many as 14, are attached to a single hair.

In the United States the other warble fly, H. bovis, has been found only in the North (New England, New York, Pennsylvania, Maryland, Michigan, Iowa, Missouri, and Washington) and has not yet been found in the Southern States. The tail is orange-yellow, lighter in color than that of the other species, and the legs have but few hairs. This fly commonly deposits its eggs on the outside of the hind quarters and above the fetlocks when the animals are moving, or lower down if they are quiet. Cattle are usually much disturbed by the activity of this fly and not infrequently appear terror stricken. The eggs are attached singly, one egg to a hair near its base.