CHOKING.—This is a common accident in cattle and horses. The object that causes the choke may be lodged in the pharynx or oesophagus. Certain individuals are more prone to choke while feeding than others. This is because of their habit of eating greedily, and swallowing hastily without properly mixing the bolus with the saliva. For this reason, choking occurs when the animal is eating dry feed. Cattle frequently become choked on pieces of such food as roots and apples that are too large to readily pass down the oesophagus. Sharp objects taken in with the food sometimes become lodged in the oesophagus or pharynx.

The symptoms differ in complete and partial choke. In the latter, the symptoms are not very characteristic. The animal may stop feeding, but shows very little evidence of suffering pain. It may be able to swallow a little water. On attempting to drink, a part of the water may be returned through the nose, the same as in complete choke. Ineffectual efforts to swallow, salivation, coughing, hurried respiration, and an anxious expression of the face occur in complete choke. Bloating may complicate this accident in ruminants. After partial choke has persisted for a day or two, the animal appears dejected or distressed. Pressure on the trachea by hard objects may cause difficult respiration.

Mechanical pneumonia sometimes occurs. This is due to the food and water that the animal may attempt to swallow, being returned to the pharynx and passed into the air passages and lungs.

The treatment is as follows: Animals that have choked should not be given access to feed of any kind. Any attempt to take food or drink water may result in pneumonia. It may be necessary to drench the animal with a very small quantity of water for the purpose of diagnosis. The most common form of choke in horses is that due to accumulation of dry food in the oesophagus. The administration of a drug that stimulates the secretion of saliva is a very successful method of relieving this form of choke. Pilocarpine is the drug commonly used. Cheap whips should not be introduced into the oesophagus for the purpose of dislodging the foreign body. There is always danger of the whip becoming broken off, and the broken part lodging in the oesophagus. Neither should such rigid objects as a broom or rake handle be introduced, because of the danger from serious injury to the walls of the pharynx and oesophagus. The flexible probang, which is usually made of spiral wire covered with leather, is a very useful instrument to relieve choke when in the hands of an experienced operator. If the object causing the choke is situated in the neck portion of the oesophagus, it may sometimes be moved forward, or toward the stomach by pressure with the fingers.

CASTRATION.—The castration of the male is a common operation in domestic animals. The purpose of the operation is to render the animal more useful for work or meat production.

The age at which the operation is performed varies in the different species. The colt is usually castrated when he is one year old, and the calf, pig and lamb when a few weeks or a few months of age. It is not advisable to castrate the young at weaning time. The operation and the weaning together may temporarily check the growth of the animal. Colts that are undeveloped and in poor flesh, or affected with colt distemper, should be allowed to recover before they are operated on. In all animals, it is advisable to wait until after they have recovered from disease and become thrifty and strong.

The spring, early summer and fall are the most suitable seasons for castrating the young. It may be practised during the hot or cold months of the year with little danger from wound infection or other complications, providing the necessary after-attention can be given.

The preparation of the animal for the operation by withholding all feed for about twelve hours is very advisable. If this is practised, the stomach and intestines are not distended with feed, and the young are cleaner, easier to handle and suffer less from castration. Clean quarters and surroundings are very necessary to the success of the operation.

The instruments required are sharp knives, preferably a heavy scalpel and a probe-pointed bistoury, an emasculator for large and mature animals, and surgeon's needles and suture material. Ropes and casting harness are frequently used for confining and casting the large and mature animals. Two clean pans or pails filled with a two per cent water solution of liquor cresolis compositus, or an equally reliable disinfectant, should be provided for cleaning the scrotum and neighboring parts and the instruments. Pieces of absorbent cotton or oakum may be used in washing and cleaning the scrotum. The instruments should be sterilized in boiling water before using.

If a number of pigs or lambs are to be castrated, it is best to confine them in a small, clean, well-bedded pen. This enables the attendant to catch them quickly and without unnecessary excitement or exercise. They should be taken to an adjoining pen to be castrated. The scrotum should be washed with the disinfectant, and the testicles pressed tightly against the scrotal wall. An incision parallel with the middle line or raphe and a little to one side is made through the skin and the coverings of the testicle, and the testicle pressed out through the incision. The testicle and cords are then pulled well out and the cord broken off with a quick jerk and twist, or scraped off with a knife. The latter method is to be preferred in large lambs if the operator does not have an emasculator. The incision in the scrotum should be extended from its base to the lowest part, in order to secure perfect drainage.

Young calves may be castrated in the standing position or when cast and held on the side. The method of operating is the same as recommended for pigs and lambs.

The castration of the colt may be performed in either the standing position or when cast. The method of operating is the same as practised in the smaller animals with the exception of cutting off the cord. The emasculator is used here. This instrument crushes the stump of the cord and prevents haemorrhage from the cut ends of the blood-vessels. Careful aseptic precautions must be observed in operating on colts, as they are very susceptible to wound infection and peritonitis.

The blood-vessels of the testicular cord are larger in the adult animals, and the danger from haemorrhage is greater than in the young. For this reason, it is advisable to use an emasculator in castrating all mature animals.

Complications Following Castration.—The haemorrhage from the wound and stump of cord is usually unimportant in the young animals. Serious haemorrhage from the vessels of the cord sometimes occur in the adult, and a persistent haemorrhage results when a subcutaneous vein is cut in making the incision in the scrotum. This complication is not usually serious, and can be prevented and controlled by observing proper precautions in cutting off the cord, or by picking up the cut ends of the vessel and ligating it. Packing the scrotal sack with sterile gauze or absorbent cotton, and closing the incision with sutures may be practised for the purpose of stopping this form of haemorrhage. The packing should be removed in about twelve hours.

The infection of the wound always follows castration. If the incision is small and the operation is followed by swelling of the neighboring tissues, the clotted blood, wound secretions and pus become penned up in the scrotal sack. Local blood poisoning or peritonitis follows. This is not an uncommon complication. It can be prevented by aseptic precautions in operating, and insuring good drainage by extending the incision to the lowest part of the scrotal sac. The scrotal sac always contracts down and becomes more or less swollen within a day or two following castration. We must keep this in mind when enlarging the opening, and be sure and make it plenty large to permit the escape of the infectious matter. In castrating sheep, all wool in the region of the scrotal sac should be clipped off, as this interferes with drainage from the wound.

Exercise following castration is almost as essential as clean quarters. Lack of exercise leads to oedematous swelling in the region of the scrotum, and the lips of the incision may become adhered if the animal is at rest. Colts and all mature animals that are confined in close quarters should be examined within forty-eight hours following the operation, and the condition of the wound noted. If closed, the hands should be cleaned and disinfected, and the adhesion broken down with the fingers. It is best to exercise horses daily.

It is unsafe to expose castrated animals to cold, damp, chilly weather. The shock and soreness resulting from the operation render the animal highly susceptible to pleurisy and pneumonia. This is especially true of young colts.

Inguinal hernia or "rupture" may complicate the operation. This form of hernia is quite frequently met with in pigs, and only occasionally in the other animals. This complication is usually overcome by practising what is commonly termed the covered operation. The pig is usually held or hung up by the hind legs. A larger animal is placed on its back. The hernia is reduced by manipulating the mass of intestines with the fingers, so that they drop back into the abdominal cavity. The part is carefully cleaned and disinfected and an incision made through the scrotal wall, and the thin covering or serous sac in which the testicle is lodged is exposed. The testicle with the cord and covering is drawn well out of the scrotum and held by an attendant. The operator then passes a needle carrying a strong silk thread through the cord and covering, below the point where he intends severing it. The needle is removed and the cord and covering ligated at this point. The cord is then cut off about one-half an inch from the ligature, and the incision in the scrotum made plenty large in order to insure drainage.

It is very essential to the success of this operation that the animal be dieted for twelve or eighteen hours before attempting to operate. The after-treatment consists in giving the animal separate quarters and feeding a light diet.

Enlarged or scirrhous cords follow infection of the wound, usually with spores of a certain fungus (Botryomyces). This complication more often follows castration of cattle and pigs than of colts. Wrong methods of operating, such as leaving the stump of the cord too long and insufficient drainage for the pus and wound secretions, are the factors that favor this complication. Scirrhous cords or fibrous tumors should be dissected out and removed before they have become large and begun breaking down.

CASTRATION OF RIDGELING OR CRYPTORCHID ANIMALS.—In the ridgeling animal one or both of the testicles have not descended into the scrotal sac, and are usually lodged in the inguinal canal or abdominal cavity. If the testicle is lodged in the inguinal canal the animal is termed a "flanker." In yearling colts the testicular cord is sometimes short, and the testicle is situated high up in the scrotum and inguinal canal. In examining a supposed cryptorchid colt, he should be twitched. This may cause the testicle to descend into the scrotum.

The castration of a true cryptorchid requires a special operation. When properly performed and the animal given special after-care, the operation is not followed by any serious complications. An abnormally large, diseased testicle is sometimes met with that cannot be removed in the usual way, and which complicates and increases the difficulty of operating.

CAPONIZING.—The castration or caponizing of the male chicken is commonly practised in certain localities. This operation changes the disposition of the cockerel. He becomes more quiet and sluggish, never crows, the head is small, the comb and wattles cease growing and the hackle and saddle feathers become well developed. A capon always develops more uniformly and is larger than the cockerel.

The best time to caponize the cockerel is when he weighs between two or three pounds. If older and heavier, the testicle becomes so large that it is very difficult to remove, and the danger from tearing the spermatic artery and a fatal haemorrhage resulting is greater.

There are several kinds of caponizing instruments. They may be purchased in sets. Each set should contain an instrument for removing the testicle; a knife for making the incision through the abdominal wall; a sharp hook for tearing through the thin membrane; spring spreader for holding the lips of the incision apart; a blunt probe for keeping the intestines out of the way of the operator; and a pair of tweezers for removing clots of blood. The different instruments for removing the testicles are a spoon-like scoop, spoon forceps and cannula. The spoon-like scoop is preferred by most operators.

The cockerel is confined for the operation by passing a strong noose of cord around both legs, and a second noose around the wings close to the body, that have weights fastened to them. The cords pass through holes or loops in a barrel or board that is used for an operating table. This holds the cockerel firmly and prevents his struggling.

The bird should be prepared for the operation by withholding all feed and water for a period of twenty-four hours or longer, for the purpose of emptying out the intestine. The operator must have a strong light, in order to work quickly and safely. Direct sunlight or electric light should be used.

The instruments should be placed in a two per cent water solution of carbolic acid. A second vessel containing a two per cent water solution of liquor cresolis compound for cleaning the skin is necessary. Absorbent cotton should be used for washing the wound.

The general method of operating is as follows: The incision is made between the last two ribs and in front of the thigh. The feathers over this region should be removed, and the skin pulled to one side before making the incision. An incision about one and one-half inches in length is made through the skin and muscles, and the spreader inserted. The sharp hook is then inserted and the thin serous membrane over the intestine is torn through. The testicles are situated in the superior portion of the abdominal cavity or under the back. On pushing the intestines to one side, both testicles, which are about the size of a bean and yellowish in color, can be seen. The lower one should be removed first. After removing both testicles, blood clots, feathers, or any foreign body that may have gotten into the wound should be picked up with the tweezers before removing the spreaders and allowing the wound to close. No special after-treatment is required.

The most common complication is rupture of the spermatic artery. This occurs at the time the testicle is torn loose and may be due to careless methods, or operating on cockerels that are too large. If all of the testicle is not removed from the abdominal cavity, the bird is termed a "slip." Sometimes air puffs form after the operation. These should be punctured with a sharp knife.

OVARIOTOMY, "SPAYING."—The removal of the ovaries, or ovariotomy, is practised for the purpose of rendering the female more useful for meat production, prolonging the period of lactation, overcoming vicious habits and preventing oestrum or heat. The operation is commonly performed in the heifer and bitch, occasionally in the mare, and at present rarely in the sow.

Heifers are usually spayed between the ages of eight and twelve months; the bitch and sow when a few months old, or before the periods of heat have begun. The mare is spayed when mature. It is possible to spay the female at any age, but the ages mentioned are the most convenient. Pregnant animals should not be operated on. The season of the year makes little difference in the results, providing the animal can be kept under close observation and given the necessary care and treatment. The spring of the year, just before turning the herd on pasture, is the best season to spay heifers.

All animals should be prepared for the operation by withholding all feed for at least twenty-four hours before they are operated on, and it may be advisable to give them a physic. It is easier to operate when the intestinal tract is comparatively empty, and the death rate is lower than when the animal is not properly prepared for the operation.

The method of operating is not the same in the different species. In young heifers and sows, the flank operation is preferred, and in mares and cows, the vaginal operation. The median line operation is practised in bitches. A spaying emasculator, or ecraseur, are the special instruments need for removing the ovaries.

The animal must be properly confined for the operation. Heifers are usually held in the standing position by fastening the head securely, and crowding the left side of the animal against a solid board partition, or side of a chute. If the vaginal operation is performed, the mare or cow may be confined in stocks. The bitch is usually anesthetized and placed on her back on a table that is inclined, so that the hind parts are elevated.

Ovariotomy cannot be successfully performed by an untrained and inexperienced operator. The necessary precautions against the infection of the part must be observed, in order to promote the healing of the wound and prevent peritonitis. The seat of the operation should be carefully cleaned and disinfected.

Following the operation the animal should be fed a spare diet for a few days. This is a very necessary part of the care of the bitch. The general condition of the animal should be noted daily until there is no further danger from wound infection. Healing is usually completed in from seven to twelve days. The sutures should then be removed, and if stitch abscesses occur, the part should be washed with a disinfectant.

QUESTIONS

1. What is the purpose of dehorning cattle? Give different methods of removing the horns.

2. Give the causes and treatment of choking.

3. What is the purpose of castration and ovariotomy?

4. At what age is it best to practise castration and ovariotomy?

5. In what way should an animal be prepared for castration? Give a description of the method of castration in the different animals.

6. What special care should be given following castration?

7. What are some of the complications that may follow castration?



PART V.—PARASITIC DISEASES



CHAPTER XXIV

PARASITIC INSECTS AND MITES

Parasitic insects are common causes of skin diseases in domestic animals. The diseased conditions of the skin, and the irritation that they may cause the animal, depend on the life history and habits of the parasite. Species that are unable to live independently of a host and are permanent parasites are usually the most injurious to the animal. This is especially true of parasites that are capable of puncturing the skin or burrowing into it. Temporary parasites may cause fatal forms of disease. This is true of the larva? of the sheep bot-fly, which develop in the sinuses of the head, causing severe inflammation of these parts, nervous symptoms and death. The character of the symptoms of a parasitic disease depends on the habits of the parasite, and the tissue or organ, that it may attack.

The parasitic flies belong to the order Diptera, and the families Muscidae and OEstridae. Fleas belong to the sub-order Pulicidae. The order Hemiptera includes the lice, and the most important families are Pediculidae and Ricinidae. Mites and ticks belong to the order Acarina. The most important parasites belonging to this order are the Sarcoptidae and Ixodidae.

OESTRIDAE.—The three common bot-flies are the Gastrophilus equi, Hypoderma lineata and OEstrus ovis. These flies are important because of the parasitic habits of their larva. They inhabit the stomach and intestines of horses (Fig. 62); the subcutaneous tissue and skin of cattle; and the sinuses of the head and nasal cavities of sheep.

The common bot-fly of the horse (G. equi) has a heavy, hairy body. Its color is brown, with dark and yellowish spots. The female fly can be seen during the warm weather, hovering around the horse, and darting toward the animal for the purpose of depositing the egg. The color of the egg is yellow, and it adheres firmly to the hair. It hatches in from two to four weeks, and the larva reaches the mouth through the animal licking the part. From the mouth, it passes to the stomach, where it attaches itself to the gastric mucous membrane (Fig. 62). Here it remains until fully developed, when it becomes detached and is passed out with the fasces. The third stage is passed in the ground. This takes place in the spring and early summer and lasts for several weeks, when it finally emerges a mature fly.



The bot-fly of the ox (H. lineata) is dark in color and about the size of a honey-bee. On warm days, the female may be seen depositing eggs on the body of the animal, especially in the region of the heels. This seems to greatly annoy the animal, and it is not uncommon for cattle to become stampeded. The egg reaches the mouth through the animal licking the part. The saliva dissolves the shell of the egg and the larva is freed. It then migrates from the gullet, wanders about in the tissue until finally it may reach a point beneath the skin of the back. Here the larva matures and forms the well-known swelling or warble. In the spring of the year it works out through the skin. The next stage is spent in the ground. The pupa state lasts several weeks, when the mature fly issues forth.

The bot-fly of sheep (O. ovis) resembles an overgrown house-fly. Its general color is brown, and it is apparently lazy, flying about very little. This bot-fly makes its appearance when the warm weather begins, and deposits live larvae in the nostrils of sheep. This act is greatly feared by the animals, as shown by their crowding together and holding the head down. The larva works up the nasal cavities and reaches the sinuses of the head, where it becomes attached to the lining mucous membrane. In the spring, when fully developed, it passes out through the nasal cavities and nostrils, drops to the ground, buries itself, and in from four to six weeks develops into the mature fly.

SYMPTOMS OF BOT-FLY DISEASES.—The larvae of the bot-fly of the horse do not cause characteristic symptoms of disease. Work horses that are groomed daily are not hosts for a large number of "bots," but young and old horses that are kept in a pasture or lot and seldom groomed may become unthrifty and "pot bellied," or show symptoms of indigestion.

Cattle suffer much pain from the development of the larva of the H. lineata. During the spring of the year, the pain resulting from the presence of the larvae beneath the skin and the penetration of the skin is manifested by excitement and running about. Besides the loss in milk and beef production, there is a heavy yearly loss from the damage to hides.

The parasitic life of the bot-fly of sheep results in a severe catarrhal inflammation of the mucous membrane lining the sinuses of the head, and a discharge of a heavy, pus-like material from the nostrils. The irritation produced by the larvae may be so serious at times as to result in nervous symptoms and death.

TREATMENT OF BOT-FLY DISEASES.—The treatment of the different bot-fly diseases is largely preventive. This consists in either the destruction of the eggs or the larvae.

The different methods of destroying the eggs of the bot-fly of the horse are clipping the hair from the part, scraping off the eggs with a sharp knife, or destroying them by washing the part infested with eggs with a two or three per cent water solution of carbolic acid. This should be practised every two weeks during the period when the female deposits the eggs.

Housing the cattle, or applying water solutions of certain preparations to the skin that may keep the female from depositing eggs, may be practised for the prevention of the ox-warble. The most practical method of ridding cattle of this pest is to destroy the larvae. This can be done by examining each animal and locating the swelling or warble and injecting a few drops of kerosene into the opening in the skin. A better method is to enlarge the opening in the skin with a sharp knife, squeeze out the grub and destroy it. This should be practised in late winter and early spring.

The application of pine tar to the nostrils of sheep is the most practical method of preventing "grub in the head." This should be practised every few days during the summer months. A very good preventive measure is plenty of shade for the flock. Valuable animals may be treated by trephining into the head sinus and removing the "grub."

LICE.—The sucking lice belong to the genus Hoematopinus, and the biting lice of mammals belong to the genus Trichodectes. Different species of sucking and biting lice occur on the different species of farm animals. Poultry act as hosts for many different species of biting lice belonging to the following genuses: Lipiurus, Goniodes, Goniocotes and Menopon.

The common sucking lice occurring on animals are the large-headed horse louse, H. macrocephalus; the long-nosed ox louse, H. tenuirostris; the large-bellied ox louse, H. curysternus; the H. stenopses of sheep; H. suis of swine; and the H. piliferus of the dog.

The common biting lice (Fig. 63) that are found on domestic animals are the T. pilosus and T. pubescens of solipeds, T. scalaris of the ox, T. spoerocephalus of sheep and goats, T. latus and T. subrostratus of the dog and cat. Menopon palidum, Lipiurus variabilis and Gonoides dissimilis are the common lice found on poultry.



SYMPTOMS OF LICE.—The symptoms of lousiness depend on the variety of lice present, the degree to which the animal is infested with them, its physical condition and the care that it receives. Lice multiply more rapidly and cause greater loss during the winter months than they do in the summer, when the animals are not housed and the opportunity for infection from the surroundings is not so great. The sucking louse (Fig. 64) is the most injurious and irritating. The irritation and loss of blood that the animal may suffer when badly infested by this parasite may result in marked unthriftiness. Young and old animals that are not well cared for suffer most. The biting louse may bite through the superficial layer of the skin, and cause the animal to bite and rub the part. This irritation to the skin prevents the animal from becoming rested, and after a time seriously interferes with its thriftiness.

Horses and mules show a staring, dirty, rough coat. The mane and tail may become broken and matted. The animal rubs against the stall, fences and trees, and bites the skin in its efforts to relieve the irritation. On examining the coat, nits are found adhering to the hair (Fig. 65). We should examine the parts of the skin covered by the long hair for the sucking lice; and the withers, abdomen and limbs for the biting lice.



The symptoms of lousiness in cattle are about the same as occur in horses. Licking and rubbing the skin are prominent symptoms in cattle, and the coat becomes dirty and rough. The licked part is matted and curled. The lice may be discovered by parting the hair along the back and rump.

The biting louse of sheep causes the fleece to become matted and tufts of wool are pulled out. This is brought about by the sheep rubbing and nibbling the fleece, and the lice cutting through the wool. The loss due to the damage to the fleece is usually greater than that resulting from unthriftiness.

The hog-louse is the largest specie known. As well as the largest, it is the most common of all lice found on domestic animals. The favorite points of attack are the under surface of the body, the neck and the inside of the thighs. The irritation and itching are severe, and the hog rubs and scratches the skin. Young hogs suffer most from this parasite, and their thriftiness is greatly interfered with.

The long-haired breeds of dogs suffer more from lice than the short-haired breeds. The almost constant scratching and biting of the skin result in its becoming badly irritated and scabby. The symptoms differ little from irritation to the skin caused by fleas, but the presence of biting or sucking lice enables the person making the examination to determine the cause of the irritation.

Lice are the most common parasites of poultry. It is uncommon to meet with a flock of fowls that are not hosts for one or more of the many different varieties of bird lice. Restlessness, picking, scratching, flapping the wings, abandoning the nest and loss of condition are common symptoms. Young birds suffer most from lice. This is especially true of young chickens, death frequently resulting. Old fowls may show little inconvenience unless badly infested. The finding of the lice with the head imbedded in the skin or on the feathers enables the person making the examination to positively diagnose the case. The head, back, region of the vent and beneath the wings are the parts that should be carefully examined for lice.

TREATMENT OF LOUSINESS.—The preventive treatment is very important. This consists in carefully examining all animals or birds that have been purchased recently, and if found to harbor lice, excluding them from the herd or flock until after they have been properly treated.

It is impossible to rid animals of lice if the quarters are thoroughly cleaned and disinfected. This is necessary in order to destroy lice that have become scattered about by the lousy animals, and prevent the reinfection of the treated animals. The best method to use in cleaning the quarters is to remove all litter and manure from the stable or houses and their immediate surroundings. It should be burned, or hauled to a field or lot where other animals cannot come in contact with it for a few months. The walls, floors and partitions should be sprayed with a three per cent water solution of liquor cresolis compositus. Lime may be scattered about the buildings, yards and runs. The most satisfactory method of destroying lice on the bodies of animals is by washing or dipping in a water solution or mixture of some reliable disinfectant or oil.

Running hogs through a dipping tank that contains a one or two per cent water solution of liquor cresolis compositus, or a coal tar disinfectant, or that has from three-fourths to one and one-half inches of oil on top of the water, is the most satisfactory method of destroying the hog louse. Because of the thinness of the hog's coat and the danger from irritating the skin when strong solutions of a disinfectant are used, most swine breeders prefer crude oil as a remedy for lousiness in hogs. Crude oil may be applied to the bodies of hogs with a swab. If this method is practised instead of dipping, it is advisable to crowd the hogs into a small pen, and apply the oil in front and between the thighs and back of the arms. This may be practised during the cold weather when it is impossible to dip the animals.

Horses may be washed with a one or two per cent water solution of liquor cresolis compositus, or a coal tar disinfectant. If the weather is cold, it is advisable to pick a sunny day, and blanket the animal after rubbing it as dry as possible in order to prevent chilling and catching cold.

Cattle may be treated in the same manner as horses. Mercurial ointment rubbed in small amounts on the skin back of the horns and ears, where the animal cannot lick it, is a common remedy. The absorption of a small amount of this drug does the animal no harm, but a larger quantity may salivate it.

Sheep are treated by dipping in a water solution of a reliable coal tar disinfectant. This should not be practised during cold weather, as the fleece does not dry out. Insect powder may be dusted into the fleece when it is impossible to dip the animal.

A very satisfactory treatment for lousiness in dogs and cats is to wash them with carbolized soap. We should wait a few minutes before rinsing off the soapy lather and drying the coat.

A number of different remedies are used for the treatment of lousiness in poultry. Dust baths and insect powder are recommended. Ointments are commonly used. One part sulfur and four parts vaseline, or lard, may be made into an ointment and applied to the head, neck, under the wings and around the vent. Mercurial ointment may be applied to the margin of the vent. Neither of them should be used for destroying lice on young chicks. Mercurial ointment should be used very carefully because of its poisonous effect. Lard may be used for destroying lice on young chicks. Crude petroleum may be sprayed among the feathers by a hand-sprayer, while the fowls are suspended by the feet.



None of the disinfectants and oils recommended for dipping and washing lousy animals destroy the nits. This makes it necessary to re-treat the animal in from eight to ten days after the first treatment.

THE SHEEP-TICK.—This is not a true tick. It resembles a fly more than it does a tick, and its right name is Melophagus ovinus (Fig. 66). Louse-fly is a better name for this parasite than tick, as its entire life is spent on the body of a sheep. The general color of the body is brown. The legs are stout, covered with hair and armed with hooks at their extremities. The mouth parts consist of a tubular, toothed proboscis with which the parasite punctures the skin and sucks the blood. Within a few hours after birth, the larvae develop into pupae, which are hard, dark brown in color and firmly glued to the wool. The young louse-fly emerges from the pupa in from three to four weeks.

The sheep-tick is a very common external parasite. The adult parasites and the pupae are large and easily found. When badly infested with ticks, a sheep will rub, dig and scratch the skin and fleece. This results in pieces of wool becoming pulled out and the fleece appears ragged. After clipping the ticks migrate from the ewes to the lambs, which may become unthrifty and weak.

The treatment consists in dipping the flock in a one or two per cent water solution of a coal-tar dip. Dips containing arsenic are most effective in ridding sheep of ticks.



SCABIES.—This parasitic disease is one of the oldest and most prevalent diseases of the skin. It is commonly known as scab or mange. The animals most commonly affected are sheep, horses and cattle.

The disease is caused by small mites or acari that are naturally divided into the Sarcoptes, which burrow under the epidermis, forming galleries; the Psoroptes, which live on the surface of the skin where they are sheltered by scabs and scurf; and the Symbiotes, which also live on the surface of the skin, but prefer the regions of the hind feet and legs.

Acari multiply rapidly and live their entire life on the body of the host. A new generation is produced in about fifteen days. Gerlach has estimated the natural increase in three months at 1,000,000 females and 500,000 males. Scab and mange are exceedingly contagious diseases.



Common sheep scab is caused by that specie of mites known as the Psoroptes communis var. ovis (Fig. 67). Any part of the body may become affected. The bites of the mites greatly irritate the skin, and the animal scratches, bites and rubs the part in its effort to relieve the intense itching. The skin becomes inflamed and scabby, the wool is pulled and rubbed out, and the fleece becomes ragged (Fig. 68). By pulling wool out of the newly infested area, or collecting skin scrapings and placing this material on black paper in a sunny, warm place, the mites may be seen crawling over the paper. This method of diagnosis should be resorted to in all suspicious cases of skin disease, and before the disease has developed to any great extent.

The mite that most commonly causes mange in cattle is the Psoroptes communis var. bovis. It may invade the skin in the different regions of the body, but it is in the regions of the tail and thighs that the first evidence of the mange is noticed. The animal rubs, scratches, and licks the part. The itching is intense. The hair over the part is lost and the skin appears inflamed, thickened, moist, or covered with white crusts. Cracks and sores may form in the skin. The examination of scrapings from the inflamed skin should be practised in order to confirm the diagnosis.

Mange in horses may be caused by either psoroptic or sarcoptic mites. Psoroptes communis var. equi seems to be the more common parasite. The itching is intense. The inflamed areas are small at first and scattered over the regions of the rump, back and neck (Fig. 69). After a time the small areas come together and form large patches, and further spreading of the inflammation results from grooming, scratching and biting the skin. Scattered, elevated eruptions on the skin from which the hair has dropped out are first noticed. These parts may show yellowish scabs. Later the skin is thickened, smooth, wrinkled, cracked, or covered with sores. Scrapings made from the inflamed areas of the skin may show the psoroptic mites.

Mange in hogs is comparatively rare. It is caused by one of the sarcoptic mites. The thin portions of the skin are usually first invaded. There are violent itching and rubbing, and small, red elevations occur on the skin in the region of the ears, eyelids or inner surface of the thighs, depending on the part first invaded. The skin becomes greatly thickened and covered with crusts and scabs. Pus formation and ulceration may occur.

TREATMENT OF SCAB AND MANGE.—A careful inspection of recently purchased animals that pass through stockyards, or are shipped from sections where scab and mange are common skin diseases, is an important preventive measure. Infected animals should be completely isolated from the herd, and kept apart from other animals until after they have been treated. Hogs that are slightly infected should be quarantined and treated. If badly affected, they should be killed, and the carcass disposed of by burning or burying.



The different remedies used in the treatment of the disease may be applied by dipping, hand dressing or washing, pouring, smearing and spotting. The first method is the most satisfactory. The last method may be used when a small area of the skin is involved, and during the cold weather. Washing or dipping the animal with a two per cent water solution of liquor cresolis compositus is an effective remedy for the psoroptic forms of scab and mange. Tobacco, lime and sulfur, and arsenical dips are recommended in the treatment of sheep and cattle. Ointments are recommended for animals that are slightly affected with mange. Lime and sulfur dips are recommended by the Bureau of Animal Industry. Small infected areas of the skin may be treated by applying sulfur-iodide ointment. The following ointment is commonly recommended: potassium sulfide ten parts, potassium carbonate two parts, and lard three hundred parts.

Sheep cannot be safely dipped for scab during the cold weather. If thickened and scabby, the skin should be scrubbed with the dip, or the animal prepared for dipping or washing by first clipping the hair or wool and scrubbing the skin with water and a good soap. In order to prevent reinfection, it is necessary to remove the animal to new quarters, or thoroughly clean and disinfect the old. It is necessary to wash or spray the fences, floors, walls, brushes and curry-combs with a disinfecting solution. Manure and other litter should be removed to a place where there is no danger from its distributing the infection.

DISEASES OF POULTRY CAUSED BY MITES.—Mites or acarina that cause diseases of poultry may live on the feathers, beneath the skin, and within the body of the fowl.

The small, red mite (Dermanyssus gallinae) remains on the surface of the body only when feeding, and spends the rest of the time under collections of filth and in cracks in the roosts and walls of the house. This parasite causes the birds to become restless, emaciated and droopy.

A very small mite (Sarcoptes mutans) is the cause of scaly leg. It lives under the skin. The joints of the feet appear affected, and the foot and leg become enlarged, roughened and scaly.

Depluming scabies is caused by Sarcoptes laevis var. gallinae. This mite causes the feathers to break off at the surface of the skin. Masses of epidermic scales may form around the broken ends of the feathers. The diagnosis can be confirmed by examining the skin lesions and finding the mite.

The air sac mite (Cytodites nudus) may cause sufficient irritation to the mucous membrane lining the air sacs to seriously obstruct the air passages with mucus, or produce death from exhaustion. A post-mortem examination of a fowl that has died of this disease shows the mites on the surface of the lining membrane of the air-sacs. They appear as a white or yellow dust.

TREATMENT OF POULTRY DISEASES CAUSED BY MITES.—Diseases of poultry caused by mites may be prevented by quarantining all recently purchased birds for a period of from two to four weeks, and by keeping the poultry houses clean. Birds that are found infested with parasites should be destroyed or returned. In case the bird is valuable and suffering from external parasites only, it should be given the necessary treatment.

Red mites may be destroyed by thoroughly cleaning the poultry house, and spraying the roosts, nests, walls and floor with a three per cent water solution of liquor cresolis compositus. This should be repeated twice a week for two weeks.

Scaly-leg may be treated by applying a penetrating oil to the feet and lower part of the leg. It is advisable to first remove the scales by scrubbing the part with soap and warm water. Dipping the feet in a mixture of kerosene one part and linseed oil two parts is recommended. This should be repeated as often as necessary.

QUESTIONS

1. Describe the different bot-flies.

2. Give the life history of the bot-fly of the horse; of the ox; of sheep.

3. Give the symptoms of bot-fly diseases.

4. Give the symptoms of lousiness.

5. Give treatment for lousiness of different farm animals.

6. What is the damage from the sheep-tick? Give treatment.

7. Describe the injury from scabies and mange.

8. Give treatments for these diseases.

9. Mention the several poultry mites and tell how to treat them.



CHAPTER XXV

ANIMAL PARASITES

The common parasitic diseases of domestic animals are caused by the following groups of worms: Flukes or trematoides; tapeworms or Cestoides; thorn-headed worms or Acanthocephales; and round-worms or Nematoids. Flat worms, such as tapeworms and flukes, require secondary hosts. The immature and mature forms of tapeworms are parasites of vertebrate animals, but an invertebrate host is necessary for the completion of the life cycle of the fluke. The hog is the only specie of domestic animals that becomes a host for the thorn-headed worm. The round-worm is a very common parasite. There are many species belonging to this class.



DISTOMA HEPATICUM (COMMON LIVER FLUKE).—Sheep are the most common hosts for this parasite. It is present in the gall ducts and livers, and causes a disease of the liver known as liver rot. The liver fluke is flat or leaf-like and from thirteen to fifteen mm. long (Fig. 70). The head portion is conical. It has an oval and ventral sucker, and the body is covered with scaly spines. The eggs are oval and brownish in color.

The life history, in brief, is as follows: Each adult is capable of producing an immense number of eggs which are carried down the bile ducts with the bile to the intestine, and are passed off with the faeces. Under favorable conditions for incubation, such as warm, moist surroundings, the ova or eggs hatch and the ciliated embryos become freed. The embryo next penetrates into the body of certain snails and encysts. The sporocyst, as it is now called, develops into a third generation known as redia which escape from the cyst. The daughter redia or cercaria, as they are now termed, leave the body of the snail and finally become encysted on the stems of grass, cresses and weeds. When taken into the digestive tract of the animal grazing over infested ground, the immature flukes are freed by the digestive juices. They then pass from the intestine into the bile ducts. The period of development varies from ten to twenty weeks; each sporocyst may give rise to from five to eight redia and each redia to from twelve to twenty cercaria.

Fluke diseases occur among animals pastured on low, wet, undrained land. Drying ponds and lakes are the homes of the fresh water snails, and in such places there are plenty of hosts for the immature flukes. Wet seasons favor the development of this parasite. Cattle and sheep that pasture on river bottom land in certain sections of the southern portion of the United States are frequently affected with fluke diseases.

The symptoms of liver rot of sheep may be divided into two stages. The first stage is marked by increase in weight and improved condition. In the second stage of the disease, the animal shows a pale skin and mucous membrane, dropsical swellings, loss of flesh and weakness. The character of the symptoms of the disease depends on the age of the animals and the care that they receive. Young, poorly cared for animals suffer severely from the disease, and the death rate is usually heavy. The finding of fluke ova in the faeces is conclusive evidence of the nature of the disease. It may be advisable to kill one of the sick animals, and determine the nature of the disease by a post-mortem examination.



The treatment is preventive. Drainage water from a pasture infested with snails harboring immature flukes is a source of infection, and should not be used as a water supply for cattle and sheep. In sections where the disease is prevalent, sheep should not be pastured on low, poorly-drained land. Such land should be used for pasturing horses and cattle, but if possible, it should be first drained and cultivated. Careful feeding and good care may help the affected animals to recover.



TAPEWORMS OR CESTOIDES.—Tapeworms are formed by a chain of segments, joined together at their ends, and are flat or ribbon-shaped (Fig. 71). The head segment is small, and possesses either hooks or suckers. It is by these that the worm attaches itself to the lining membrane of the intestine. The anterior segments are smaller and less mature than the posterior segments. Each segment is sexually complete, possessing both the male and female organs, and when mature, one or more of them break off and are passed out with the faeces. The mature or ripe segments are filled with ova. On reaching the digestive tract of a proper host, usually with the drinking water or fodder, the embryo is freed from the egg. The armed embryo uses its hooklets in boring its way through the wall of the intestine. It then wanders through the tissues of its host until it finally reaches a suitable place for development (Figs. 71 and 73). On coming to rest, it develops into the larva or bladder-worm, which when eaten by a proper host gives rise to the mature tapeworm.

The following tables give the most important tapeworms:

ADULT FORMS

Name Host Organ

Taenia expansa Sheep and ox Intestine Taenia fimbriata Sheep Liver Taenia denticulata Cattle Intestine Taenia alba Cattle Intestine Taenia perfoliata Solipeds Intestine Taenia mamillana Solipeds Intestine Taenia echinococcus Dog Intestine

LARVAL FORMS

Name Host

Cysticercus bovis Cattle Cysticercus cellulosa Swine and man Cysticercus tennicollis Cattle, sheep and swine Coenurus cerebralis Cattle and sheep Echinococcus polymorphus Cattle, sheep, swine and man

The adult tapeworms Taeniae saginata and soleum, of which the Cysticerci bovis and cellulosa are the larvae forms, occur in man. The larvae are present in meat and pork, and this form of parasitism is termed beef measles in cattle and pork measles in hogs. Man becomes host for these two forms of tapeworms through eating measly pork or beef that is not properly cooked.

The dog is the host for Taeniae marginala, coenurus and echinococcus. The larvae forms of these taeniae are the Cysticercus tennicollis, Coenurus cerebralis and Echinococcus polymorphus. C. tennicollis is a parasite of the serous or lining membranes of the body cavities. It is not of great economic importance. C. cerebralis is a parasite of the brain of sheep, and may cause a heavy death rate in flocks that are infested with it. E. polymorphus is a parasite of the liver, but it may occur in other organs.

THE THORN-HEADED WORM OR ACANTHOCEPHALE.—This parasite requires a secondary host. In this case a particular species of the May-beetle larva or white grub that is commonly found about manure piles and in clover pastures is the host. The hog eats a white grub that is host for the larval form. The digestive juices free the larva, it then becomes attached to the intestinal mucous membrane and develops into the adult thorn-headed worm (Fig. 74). This parasite is characterized by a hooked proboscis or thorn at its anterior extremity, and the absence of a distinct digestive tract. The male is much smaller than the female. The eggs are passed out of the intestine with the faeces.



THE ROUND-WORMS OR NEMATOIDS.—Round-worms are very common parasites of domestic animals (Fig. 75). This group of worms is characterized by their cylindrical form, the presence of a true digestive canal and the separation into two sexes, male and female. The life history is more simple than in the flat worms. Intermediate hosts are not required for the development of the common forms. The eggs and embryos are deposited by the female in the intestinal tract, air passages, or excretory ducts of the kidneys of the host. Development may be completed here, or the eggs and embryos are passed off with the body excretions. They may live for a short time outside the animal body, or undergo certain development and again infest a host of the same species from which they came, through the water, grass and fodder that the animal may take into its digestive tract.



The following species of nematoids are common parasites of domestic animals:

SOLIPEDS

Species Organ Ascaris megalocephala Intestines Sclerostoma equinum Large intestine and blood-vessels Sclerostoma tetracanthum Large intestine Oxyrus curvula Large intestine Oxyrus mastigodes Large intestine

CATTLE

Species Organ Strongylus convolutus Abomasum Ascaris vituli Small intestine (calves) Strongylus ventricosus Small intestine Oesophagostomum inflatum Large intestine Trichocephalus affins Large intestine Strongylus micrurus Bronchi Strongylus pulmonaris Bronchi

SHEEP

Species Organ Haemonchus contortus Abomasum Ascaris ovis Small intestine Strongylus filicollis Small intestine Oesophagostomum columbianum Intestines Uncinaria cernua Small intestine Trichocephalus affins Large intestine Strongylus filaria Bronchi Strongylus rufescens Bronchi and air follicles

SWINE

Species Organ Ascaris suis Intestines Oesophagostomum dentatum Large intestine Trichocephalus crenatus Large intestine Trichina spiralis Muscles and intestines Strongylus paradoxus Trachea and bronchi Sclerostoma pingencola Renal fat and kidney

POULTRY

Species Organ Ascaris inflexa Intestine Spiroptera hamulosa Gizzard Heterakis papillosa Caecum Syngamus trachealis Trachea and bronchi

INTESTINAL WORMS OF SOLIPEDS.—The large round-worms or ascarides and the sclerostomes are the most injurious intestinal parasites of solipeds. The A. megalocephala or large round-worm is from 5 to 15 inches (12 to 35 cm.) long. It may be present in the double colon in such large numbers as to form an entangled mass that completely fills a portion of the loop in which it is lodged. It may interfere with digestion by obstructing the passage of alimentary matter, and irritating the intestine.

The S. equinum and S. tetracanthum are small worms. The former sclerostoma is from 0.6 to 1.5 inches (18 to 35 mm.) long, and the latter is from 0.5 to 0.6 inch (8 to 17 mm.) long. Both sclerostomes attach themselves to the lining membrane of the intestine by their mouth parts, and suck blood. The young S. equinum may live in tumor-like cysts that they cause to form in the lining membrane of the intestine. The young worm may penetrate the wall of a small blood-vessel as well, and drift into a large vessel, where it may become lodged and undergo partial development. The irritation to the blood-vessel results in an inflammation and dilation of the vessel wall. This is termed verminous aneurism. A portion of the fibrin-like lining of the aneurism may flake off and drift along in the blood stream, until finally a vessel that is too small for the floating particle or embolus to pass through is reached. The vessel is then plugged or a thrombus is formed. If the vessel involved by the thrombus happens to be a mesenteric vessel, then a loop of intestine has its blood supply cut off, and colicky pains result. Such colics are dangerous, and may terminate fatally. Intestinal obstruction, thrombo-embolic colics, unthriftiness and a weakened, anaemic condition may be caused by intestinal worms.

The treatment is both preventive and medicinal. The preventive treatment consists in giving young, growing animals the best care possible. Cleanliness about the stable, giving the colt plenty of range when running in a pasture, and feeding a ration that is sufficient to keep the colt in good physical condition are the important preventive measures. Tartar emetic in one-half to one dram doses may be given with the feed daily until five or six doses are given. Turpentine may be given in one to three ounce doses in a pint of linseed oil. This may be repeated daily for two or three days. Worms located in the posterior bowel may be removed by rectal injections of a weak water infusion of quassia chips. The rectum should be first emptied with the hand, and the nozzle of the syringe carried as far forward with the hand as possible. The injections should be repeated daily for several days.

INTESTINAL WORMS OF CATTLE.—Intestinal worms seldom cause serious losses from unthriftiness or death in cattle. It is in calves only that we are called on to treat this class of disease. The symptoms resulting from the invasion of the intestinal tract by the different worms vary in severity according to the number, habits of the parasite and care that the animal receives. The usual symptoms are unthriftiness, indigestion, diarrhoea and a stunted, anaemic condition. Stiles reported extreme anaemia, unthriftiness and many deaths among cattle in a certain section of Texas, due to extensive infection with the Uncinaria radialus.

The treatment is largely preventive. Calves and yearlings should be provided with plenty of feed at all seasons of the year. Good care and careful feeding will keep them in a thrifty, healthy condition and enable them to throw off invasions of intestinal worms. Turpentine is the vermifuge usually administered to calves. The dose is from two to four drams given in a milk or raw linseed oil emulsion.

STOMACH WORM OF SHEEP.—The twisted stomach worm, Haemonchus contortus, is the most injurious internal parasite of sheep. It is a very small, hair-like worm from 0.4 to 1 inch (9 to 25 mm.) in length. In the adult form it attaches itself to the mucous membrane of the fourth stomach or abomasum, and lives by sucking blood. The blood present in the digestive tract of the worm gives it a brown color, and the white oviducts which are wound around the digestive canal cause the body to appear twisted. When the twisted stomach worm is present in large numbers, the worms become mixed with the contents of the stomach and can be readily found on making a post-mortem examination.

Symptoms of stomach worms are first manifest in the lambs (Fig. 76). It is not until early summer that the disease appears in the flock. The symptoms are not characteristic unless we consider an unthrifty, anaemic, weak, emaciated condition accompanied by diarrhoea, during the summer months characteristic of stomach-worm disease. The sick animals are unable to keep up with the flock, and they like to stand about in the shade. They move slowly, the back is arched, the appetite poor, the mucous membranes and skin are pale and the hind parts soiled by the diarrhoeal discharge. More acute symptoms than the above sometimes occur. The disease may last from a few days to several weeks. A large percentage of the affected animals die.



The treatment is largely preventive. Frequent changing of pastures and dry lot feeding are common preventive measures. Permanent sheep pastures lead to heavy losses from stomach worm disease. A very effective preventive measure, as we may term it, is the practice of administering a vermifuge to the ewes in the late summer and again in early winter. This may be given in a drench, or with the feed. This prevents the reinfection of the pastures every spring, and the young lambs are not exposed to this form of infection. The most effective treatment that the writer has ever used is the following formula recommended by Dr. Law: Arsenous acid one dram, sulfate of iron five drams, powdered areca nut two ounces, common salt four ounces. This is sufficient for one dose for thirty sheep. It may be given with the salt, or in ground feed. If the flock is apparently healthy, four doses given at intervals of three days is sufficient. If symptoms of stomach worms are manifested the animals should be dosed daily until they have received from five to ten doses, depending on the condition of the animal.

INTESTINAL WORMS OF SHEEP.—The most widely distributed and seemingly most injurious intestinal worm of sheep is the OEsopliagostomum columbianum. It is a small worm from 0.5 to 0.75 inch (12 to 18 mm.) long. It penetrates the lining membrane of the intestines and encysts in the intestinal wall. A tumor, varying in size from that of a millet seed to a hazelnut, then forms in the wall of the intestine. These tumors undergo a cheesy degeneration, and when mature, may appear as greenish, cheesy-like masses, covering a large portion of the lining membrane of the intestine. Diarrhoea and emaciation may result. These symptoms are most evident during the winter months.

The treatment recommended for ridding sheep of this intestinal worm is largely preventive. Very little can be done with the medicinal treatment of a sheep whose intestinal tract is badly infested with this parasite. Good care and the feeding of a proper ration are the only curative measures that are effective in such cases. The occasional administration of a vermifuge for the purpose of ridding the digestive tract of worms, together with the frequent changing of pastures during the spring and summer, are the most effective preventive lines of treatment. The same treatment recommended for stomach worms may be used for this disease.

INTESTINAL PARASITES OF HOGS.—The Ascaris suis or common round worm is very commonly found in the small intestine. It is quite frequently found in large numbers, almost filling the lumen of the intestine of an unthrifty pig (Fig. 75). It may also work its way into the bile duct. Sometimes, after a hog has died, this parasite migrates forward into the stomach and gullet. The A. suis is from 4 to 10 inches (10 to 26 cm.) long.

The Echinorhynchus gigas or thorn-headed worm is the most dangerous of all intestinal worms (Fig. 74). It is usually found with its proboscis or thorn imbedded in the wall of the small intestine. The Echinorhynchus is not as common a parasite as the Ascaride, and it is not usually present in large numbers. Usually, not more than a half-dozen of these worms are found in the intestine of a hog, but in some localities and in hogs that are allowed to root around manure piles and in clover pastures the herd may become badly infected with them and serious losses occur. The average length of the male is about 3 inches (8 cm.) and the female 10 inches (26 cm.).



The Trichocephalus crenatus or whip worm (Fig. 77) is slender or hair-like in its anterior two-thirds and thick posteriorly. It is from 1.5 to 2 inches (40 to 45 mm.) long. It is found in the caecum attached to the wall by the hair-like portion.

The OEsophagostomum dentatum or pin worm is from 0.3 to 0.6 inch (8 to 15 mm.) long. It is found in the large intestine (Fig. 78).

The symptoms of intestinal worms are not very evident in the average drove of hogs. None of the other farm animals are such common hosts for intestinal worms as hogs. But it is only in extreme cases of infection by intestinal worms, and in stunted and poorly-cared-for hogs, that very noticeable symptoms of disease are manifested. We must not take from the above statement that it is unnecessary to resort to treatment unless in exceptional cases. Intestinal worms interfere with the growth of young hogs, and may irritate and inflame the intestine, causing chronic indigestion, nervous symptoms, and in some cases death. This irritated and inflamed condition of the intestine is best noted in the abattoir by the ease with which the wall of the intestine that contains large numbers of worms tears when handling it.

The treatment of intestinal worms in hogs is both preventive and medicinal. If the conditions in the pens and houses are such as to enable the eggs and embryos to live for a long time, or the surroundings are favorable for infection of the animals through their feed and water supply, the herd may become badly infested with intestinal parasites. The preventive treatment consists in keeping hogs in clean, well-drained yards or pastures, and feeding them from clean troughs and concrete feeding floors that can be washed, when necessary, in order to keep them clean. Turpentine, given in a milk emulsion, is a common remedy for intestinal worms in hogs. The dose is one teaspoonful for every eighty pounds weight. This dose should be repeated daily for three days. The following vermifuge can be recommended: Santonin three to five grains, calomel five to eight grains. This is sufficient for one hundred pounds weight. If the pigs are small and it requires two or three to weigh one hundred pounds, the large dose should be given. If the hogs weigh one hundred pounds or more, they should receive the small dose. The drove should be divided into lots of ten or fifteen hogs each. The drugs should be mixed and divided into the same number of powders as there are lots of hogs. Ground feed is placed in the trough, dampened with milk, or water and the powder sprinkled evenly over it. The hogs are then allowed to eat the feed. It is best to dose them in the morning after they have been off feed for ten or twelve hours.

VERMINOUS BRONCHITIS IN CALVES.—The lung worms of cattle, Strongylus micrurus and Strongylus pulmonaris, may cause heavy losses in calves and yearlings. Older cattle may harbor these parasites, but they do not seem to be inconvenienced by them. The S. micrurus is from 1 to 3 inches (25 to 75 mm.) long. The S. pulmonaris is smaller. It is from 0.4 to 1.3 inches (10 to 35 mm.) long. They are found in the trachea and small bronchial tubes, where they are mixed with mucous secretions from the inflamed lining membrane of the bronchial tubes.

Wet seasons and low, wet pastures are said to favor the development of lung worms. Their life history is not fully understood. They do not persist generation after generation in the air passages of an animal, but the eggs and embryos are expelled and live for a time outside of the animal, when they may again become parasites of another or the same host.

The symptoms are the same as occur in bronchitis and pneumonia. Calves and yearlings are the only animals in the herd that may show symptoms of the disease. The air passages become irritated and inflamed, and the calf shows a slight cough. As the inflammation increases and the worms and mucous secretions plug up the small bronchial tubes, the coughing spells become more severe and rattling, wheezing sounds may be heard on auscultating the lungs. The calf finally loses its appetite, becomes emaciated and weak, and wanders off alone. It is usually found lying down and shows labored breathing that is occasionally interrupted by paroxysmal coughing. The death rate in poorly-cared-for herds is heavy.

VERMINOUS BRONCHITIS AND PNEUMONIA OF SHEEP.—The two lung worms of sheep are the Strongylus filaria and Strongylus rufescens. The former is from 1.3 to 3 inches (33 to 80 mm.) long, and the latter from 0.6 to 1 inch (16 to 25 mm.) long. The S. filaria is thread-like and the S. refuscens hair-like in appearance. For this reason they are termed thread and hair lung-worms. The thread-worm is found in the trachea and the larger bronchial tubes, and the hair-worm in the most minute as well as the larger bronchioli.

This disease is most common in wet seasons. Undrained pastures and ponds are said to favor the spread of the disease. Permanent pastures favor the reinfection of the flock from year to year. The eggs and embryos are expelled in coughing, and live for a time in the pastures, pens and houses. The sheep become infected through the dust, drinking water or feed.

The symptoms of verminous bronchitis and pneumonia are quite characteristic. Lambs suffer most from these diseases. A number of animals in the flock are affected. Coughing, rapid and labored breathing, loss of appetite, emaciation and weakness are the usual symptoms noticed. When a paroxysm of coughing occurs, considerable mucus is expelled. An examination of the expectorations may result in finding a few lung worms. In poorly-cared-for flocks, and when complicated by stomach and intestinal worms, the death rate is usually heavy.

The treatment of lung-worm diseases in lambs and calves is largely preventive. We should use every possible precaution against introducing the infection into the herd or flock. It is not advisable to bring animals from an infected herd onto the premises, without subjecting them to a careful examination and a long quarantine before allowing them to stable or pasture with the other animals. Calves or lambs that show marked symptoms of disease should be given comfortable quarters, and special care and feeding. The entire herd or flock must be given the best care and ration possible. This is the only satisfactory method of treatment. Changing the pasture or lot frequently may help in ridding the premises of the infection.

VERMINOUS BRONCHITIS IN HOGS.—The lung worm, Strongylus paradoxus, is a common parasite of young hogs. It is from 0.6 to 1.6 inches (16 to 40 mm.) long. When the infection is light, the worms are found mostly in the bronchial tubes of the margin and apex of the lung.

Infection with this parasite does not depend on the humidity of the soil, or low, wet pastures containing ponds. Probably dusty quarters are responsible in large degree for this disease.

The symptoms are most evident in pigs weighing from forty to eighty pounds. The first symptom is a cough, occurring on leaving the bed, after exercise and after eating. In badly infected cases the paroxysm of coughing is quite severe. The appetite usually remains good and the thriftiness of the pig is not seriously interfered with. The feeding of a suitable ration, and the good care that is usually given young hogs, are responsible for the mildness of the disease.

The treatment that is of most importance is clean quarters, and the feeding of a ration that will keep the pig growing and healthy. The sleeping quarters should be kept free from dust. Disinfectants should be used freely about the quarters.

THE KIDNEY WORM OF HOGS.—Sclerostoma pinguicola is the kidney worm of hogs. It is from 1 to 1.5 inches (25 to 27 mm.) long, and when seen against the kidney fat it appears dark or mottled. It is usually found in the fat in the region of the pelvis of the kidney. Although the kidney worm is capable of causing inflammatory changes in the tissues surrounding the kidney and the pelvis of this organ, the disease cannot be determined by any noticeable symptom. Paralysis of the posterior portion of the body is attributed to the presence of kidney worms by stockmen. There are no data by which we may prove that the kidney worm is responsible for this disorder.

The treatment is preventive. Clean feed, pens, watering troughs and feeding floors are the preventive measures indicated here. It is useless to attempt treatment with drugs, as the worms are out of reach of any drug that may be administered.

WORMS OF THE DIGESTIVE TRACT OF POULTRY.—Poultry are often seriously infested with worms. A small number of the less injurious worms may not cause any appreciable symptoms of disease; but the fowl that harbors them is a source of infection to the other fowls. The infectious nature of parasitic disease caused by worms should be recognized more fully than at present by poultrymen.

The different species of poultry are hosts for many different species of round-worms, thorn-headed worms and tapeworms. Dr. Kaupp states that Acaris inflexa or large round-worm, Heterakis pipilosa or small round-worm, and the Spiroptera hamulosa or gizzard-worm are frequently found in fowls. The common round-worm may be found in the first portion of the intestine, and the small round-worm in the caecum. Neither of the species are dangerous unless present in large numbers. They may then obstruct the intestine, and irritate the intestinal mucous membrane. This may cause constipation, catarrhal inflammation of the intestine and diarrhoea. The gizzard-worm is the most dangerous of the parasites mentioned. The gizzard has an important digestive function, and any condition that may weaken its muscular walls may cause serious digestive disorders. This parasite may encyst in the wall of the gizzard.

The treatment of intestinal worms in poultry is both preventive and curative. The preventive measures consist in keeping the houses and runs clean. Air-slaked lime should be scattered over the runs every few weeks. The drinking places should be cleaned and disinfected daily. All possible precautions should be taken in order to prevent filth from getting into the drinking water. Epsom salts, powdered areca nut and santonin are the remedies commonly recommended for the treatment of intestinal worms. From twenty to forty grains of Epsom salts may be given. Powdered areca nut is recommended in from three to ten grain doses. Santonin may be given in from one to two grain doses. Both the areca nut and santonin may be given with the feed.

THE GAPES IN BIRDS.—The gape-worm, Syngamus trachealis, is from 0.2 to 0.8 inch (5 to 20 mm.) long. The male and female are permanently united. The male is about one-third as long as the female, and when attached to the anterior third of the female, gives the pair a forked appearance.

Fowls become infested with the gape-worm by eating the adult parasite that has been expectorated, or an earth worm that is host for the immature parasite. The embryo gape-worm is freed in the intestine, and from here they are supposed to migrate into the abdominal air sacs and to the trachea and bronchi.

The symptom are most severe in very young fowls. The affected bird opens its mouth and appears to gasp for breath, sneeze and attempt to swallow. In the severe cases the appetite is interfered with, mucus accumulates in the mouth and the bird is dull and listless. The death rate is quite high in young-chickens and turkeys.

The treatment is both preventive and curative. If the gape-worm is known to be present in the runs, the ground should be covered with lime, and the fowls moved to fresh runs if possible. The young birds should not be exposed to the infection until they are well feathered out. Antiseptics may be given with the drinking water. Disinfectants should be used freely about the poultry houses, and the quarters kept clean. The worms may be snared by inserting a stiff horse hair that has been twisted and forms a loop into the trachea. This may be dipped into camphorated oil or turpentine. This treatment should be repeated until the bird has been relieved.

QUESTIONS

1. Name the different groups of internal parasites; give examples of each.

2. What conditions favor liver rot? Give the life history of the liver fluke.

3. Name three common tapeworms; give the life history of the beef and pork tapeworms.

4. Name the common intestinal worms of horses and give the treatment.

5. Give the symptoms and treatment of stomach-worm disease of sheep.

6. Name the common intestinal worms of hogs and give treatment.

7. What species of domestic animals suffer most of verminous bronchitis? Give the treatment.

8. Name the common internal parasites of poultry and give treatment.



PART VI.—INFECTIOUS DISEASES



CHAPTER XXVI

HOG-CHOLERA

HOG-CHOLERA is a highly infectious disease of swine. It is characterized by an inflammation, of the lymphatic glands, kidneys, intestines, lungs and skin. The inflammation is hemorrhagic in character, the inflamed organs usually showing deep red spots or blotches.

Hog-cholera is especially prevalent in the corn-raising States which possess a denser hog population than any other section of the United States. In this country the loss from hog-cholera in 1913 amounted to more than $60,000,000, and it may be considered of greater economic importance than any of the other animal diseases.

SPECIFIC CAUSE.—The specific cause of hog-cholera is an ultra-visible organism that is present in the excretions, secretions and tissues of a cholera hog. De Schweinitz and Dorset in 1903 produced typical hog-cholera by inoculating hogs with cholera-blood filtrates that were free from any organism that could be demonstrated by microscopical examination or any cultural method. The term ultra-visible virus is applied to the virus of hog-cholera.

The ultra-visible virus is eliminated from the body of the cholera hog with the body secretions and excretions. Healthy hogs contract the disease by eating feed or drinking water that is infected with the virus. There are other methods of infection, but field and experimental data show that hog-cholera is commonly produced by taking the germs into the body with food and drinking water.

ACCESSORY CAUSES.—The usual method of introducing hog-cholera into a neighborhood is through the importation of feeding or breeding hogs that were infected with the disease before they were purchased, or became infected through exposure to the disease in the public stock-yards and stock-cars. The shipping of feeding hogs from one section of the country to another, and from public stock-yards, has always been productive of hog-cholera. Dr. Dorset states that more than fifty-seven per cent of the hog-cholera outbreaks are caused by visiting, exchanging work, exposure on adjoining farms and harboring the infection from year to year (Fig. 79), and more than twenty-three per cent to purchasing hogs and shipping in infected cars, birds and contaminated streams.



In neighborhoods where outbreaks of hog-cholera occur necessary precautions against the spread of the disease are not taken. The exchange of help at threshing and shredding time in neighborhoods where there is an outbreak of hog-cholera is the most common method of spreading the disease. Visiting farms where hogs are dying of cholera; walking or driving a team and wagon through the cholera-infected yards; stock buyers, stock-food and cholera-remedy venders that visit the different farms in a neighborhood may distribute the hog-cholera virus through the infected filth that may adhere to the shoes, horses' feet and wagon wheels. Cholera hogs may carry the disease directly to a healthy herd when allowed to run at large. Streams that are polluted with the drainage from cholera-infected yards are common sources of disease.

Pigeons, dogs, cows and buzzards that travel about the neighborhood and feed in hog yards and on the carcasses of cholera hogs may distribute the disease. Because of the active part that dogs, birds and surface drainage take in the distribution of hog-cholera, the practice of allowing the carcasses of dead hogs to lie on the ground and decompose is responsible for a large percentage of the hog-cholera outbreaks.

Age is an important predisposing factor. Young hogs are most susceptible to cholera, and this susceptibility can be greatly increased by giving them crowded, filthy quarters. Infection with lice, lung and intestinal worms, the feeding of an improper ration and sudden changes in the ration lower the natural resistance of a hog against disease. Pampered hogs usually develop acute cholera when exposed to this disease.

Hog-cholera is more virulent or acute during the summer and fall months than it is during the winter and spring months. After the disease sweeps over a section of country, it becomes less virulent and takes on a subacute or chronic form. Outbreaks of hog-cholera usually last two or three years in a neighborhood. This depends largely on the number of susceptible hogs that were not exposed to the infection the first season, and the preventive precautions observed by the owners.

PERIOD OF INCUBATION.—The length of time elapsing between the exposure of the hog to the cholera virus, and the development of noticeable symptoms of hog-cholera, varies from a few days to two or three weeks. The length of this incubation period depends on the susceptibility of the animal, the virulence of the virus and the method of exposure. An acute form of hog-cholera indicates a short period of incubation, and a chronic form, a long period.

SYMPTOMS.—The symptoms of hog-cholera may differ widely in the different outbreaks of the disease. The symptoms may be classified under the following forms: Acute, subacute and chronic. The acute form of hog-cholera is the most common. The early symptoms are tremors, fever, depressed appearance, marked weakness, staggering gait, constipation and diarrhoea, labored breathing and convulsions. Death may occur within a few hours or a few days. Recovery seldom occurs. In the subacute form, the symptoms are mild and develop slowly. Recovery may take place within a few days, or after extending over a week or ten days it may assume the chronic form. Very often in outbreaks of subacute cholera a large majority of the herd does not show visible symptoms of the disease. In the chronic form, marked symptoms of pleuropneumonia and chronic inflammation of the intestine are common. Ulcers and sores form on the skin and the hair may come off. Large portions of the skin may become gangrenous and slough. Young hogs are usually stunted and emaciated.

The first symptom of disease is an elevation of body temperature.

At the beginning of any outbreak of hog-cholera the body temperatures of the apparently healthy animals may vary from 105260 to 108260 F. After a few days, animals that are fatally sick or recovering from the disease may show normal or subnormal body temperature.

Loss of appetite is the first symptom of disease usually noted by the person in charge of the herd. The hog may show a disposition to eat dirt. The sick hog is usually found lying in its bed, or off by itself in a quiet place. It presents a rather characteristic appearance. The back is arched, the hind feet are held close together, or crossed, the abdomen is tucked up and the hog appears weak in its hind parts. Diarrhoea or constipation may be present. The color of the diarrhoeal discharges varies according to the character of the feed, and it may be more or less tinged with blood and have a disagreeable odor. The urine is highly colored.

The respirations and pulse beats are quickened and abnormal in character. Thumps sometimes occur. When the mucous membranes lining the throat and anterior air passages are thickened, the respirations are noisy and difficult. The animal may cough on getting up from its bed and moving about. There is at times a noticeable discharge from the nostrils. When the lungs are inflamed the respirations are quickened and labored. In case the pleural membrane is inflamed, the respiratory symptoms are more severe, and the hog shows evidence of pain when the walls of the chest are pressed on. The pericardium may be inflamed. In such cases the hog staggers and falls when forced to walk.

The central nervous system may be involved by the inflammation. The usual symptoms occurring in inflammation of the brain and its coverings are then present. A sleepy, comatose condition may end in death, or the animal dies in a convulsion.

The secretions of the skin and mucous membranes are abnormal. The skin in the regions of the ears, inside of the thighs and under surface of the body is moist, dirty or discolored red. Just before death the skin over the under surface of the body becomes a purplish red. In the chronic form, a dirty, thickened, wrinkled skin is commonly observed. At first the secretion from the eyes is thin and watery, but it becomes thick, heavy and pus-like, causing the margins of the lids to adhere to each other.

The death rate in hog-cholera varies in the different forms of the disease. The average death rate is about fifty per cent.

DIFFERENTIAL DIAGNOSIS.—The diagnosis of hog-cholera in the field must depend on the clinical symptoms, post-mortem lesions and history of the outbreak. The history should be that of a highly infectious disease.



Abnormal body temperatures of a large percentage of the herd indicate the presence of an acute infectious disease. We should then destroy one of the sick hogs and make a careful post-mortem examination (Fig. 80). An early diagnosis of the disease is necessary, as this enables us to use curative treatment when it will do some good, and take the necessary steps toward preventing the spread of the disease to neighboring herds.

Intestinal and lung worms are common in young hogs. The presence of these worms does not always indicate that they are the cause of the sickness and death of the animal. Such parasites are injurious and may cause disease, but it is only in rare cases that they cause death.