PRINCIPAL PARASITES OF DOMESTIC ANIMALS. Perhaps the commonest worm infesting the horse is A searis megolocephala or coinnion buithricoid. The males are from 6 to 8 inches long, females 7 to 17 inches. It is found in almost every part of the intestinal canal, but generally in the small intestines. The symptoms produced in the horse by this worm are colicky pains, which occur intermittently, an unhealthy condition of the skin, and staring coat. Although the animal feeds well, it does not improve in condition, but is very "tucked up," and the visible mumps membranes are very pale. In some instances pouches are formed in the coats of the intestines. There are many recipes for the expulsion of lumbricoid ; among the principal remedies is a mixture of emetic tartar, oil of turpentine, and linseed oil ; others are saritonine, sulphate of iron, male fern, &c. Strong gins armatus or palisade worm was at first supposed to consist of two varieties, but it has been proved that these are simply different stages of growth of one parasite. It is a moderate-sized Neniatoid worm, having a straight hotly, with a globular and somewhat flattened head, - males 1 to 1 inches long, females 1 to 2 inches. It is found in the intestines, especially the double colon and cfeeum. The embryo is developed in the interior of the egg after its expulsion from the host, and is lodged in moist mud, where, according to Colthold, it changes its first skin in about three weeks, after which it probably enters the body of an intermediate bearer, whence it is conveyed to the alimentary canal of the horse, its ultimate host, in food or water. From the stomach it bores its way into the blood-vessels, where it again changes its skin and gives rise to aneurisms. After a time it recommences its wanderings, and passes into the large intestines, where it rapidly acquires sexual maturity. It is a dung-feeder. Sometimes it passes into other tissues of the body (kidney, liver, ice.), and occasionally produces fatal results. This parasite is most dangerous to its equine host when it is migrating from one organ to another. It is principally found at the root of the anterior mesenteric artery, but it also gives rise to aneurism in the coeliac axis, the post-mesente•ic and splenic arteries, and even the aorta. The common /umbricoid, the palisade worm, and the fourspined strongyle (S. te(racauthus)nre principally productive of colic. The last-mentioned worm, of which the male and female are about the same size, to 2 inch long, is found in the crecum, colon, and duodenum. It is a true blood-sucker, and its development is very similar to that of S. ormatus, except that, when in the intestines in the trichonemous stage, it pierces the inner coats, encapsnles itself, and forms little pill-like masses, and then again enters the tissues of the intestines before becoming mature. The symptoms of its presence are loss of condition, more or less constant colicky pains, unhealthy coat, flabby muscles, abdominal distension, diarrhea, fmtid and watery feces, pale mucous membranes, great weakness, more or less frequent cough, and sometimes partial or complete paralysis, due to the formation of a clot of blood causing thrombosis of one of the principal vessels of the posterior extremities, thus interfering with the circulation of blood in the part supplied by the particular vessel. The treatment by which the common Innibricold is expelled will suffice to expel these strongyles, but care must be exercised in administering oil of turpentine, as it very often irritates the wounds caused by S. tetracanaus in the coats of the intestines. Of course this treatment applies to the mature stage of these worms.
Oxyuris esenvula or pin worm is fusiform in shape, with smooth gently curved body (males 1 to 12 inches, females 3i to 4/ inches long). It is seated in the etectun and colon ; and, although not found in the rectum, it causes great irritation at the anus by the clusters of eggs which are deposited around that part in the form of yellowish crusts. This parasite is best treated by means of a cathartic, followed by sulphate of iron, also carbolic acid in 2; per cent. solution.
The Cestodes of tire horse are very insignificant, both as regards their size and the symptoms they create, the two principal being Tomio perfoliate and 7'. plicate. The former is the more common, lint is only from 1 to 5 inches in length ; it is found in the mecum and colon, and is distinguished from T. plicate, not only by its length, but also by its rounder head. This last, which has a nearly square head, and is from 6 inches to 3 feet in length, occurs in the small intestines and stomach. Generally a horse may be proved to be infested with tape-wo•m by finding some of the proglottides in the fices. The best remedy for the removal of TEenia is extract of male fern, with oil of turpentine and linseed oil, given three days ill succession.
gastrus cqui the common hot, though not a true helminth (see INsEcTs, vol. xiii. p. 150), is classed with the parasites on account of its larval form living as a parasite. The bot•fly deposits its eggs on the hair of horses in such a position as to enable that animal, when licking itself, to take them into its mouth ; there the warmth and moisture of the tongue, combined with the pressure of licking, cause them to burst, and from each egg a small grub escapes, which sticks to the tongue, and then passes down into the stomach, where it fixes itself to the cuticular lining of the organ by a hook which it has on each side of its month. There it undergoes no change (except that of growth, being at this time about 1 inch long) for about nine months, when it detaches itself, passes into the food, and is discharged with the faeces.
Of the parasites which infest cattle and sheep mention will only I be made of Faseiota hepatica or common Iluke, which gives rise to the disease called rot, and is more frequently met with in sheep than in cattle. For a full description of its anatomy and development, see TREMATODA, VOL xxiii. p. 535.
Stronolus mierarus is the husk-producing worm of cattle. The common earthworm is the intermediate bearer. S. filaria, or the common lung strongyle of sheep, is distinguished from S. mierarus by having no papillre on its head. The males are 1 inch to 1 inch 2 lines long and the females nearly 3 inches. The development is unknown ; but Cobbold thought that in its larval form the creature infestod snails, &c. The symptoms of its presence in the sheep are a dull expression, quickened breathing, foetid breath, foaming at the mouth and nostrils, violent and spasmodic cough, loss of appetite, and emaciation. Of various specific remedies the most successful is a mixture of oil of turpentine, linseed oil, and sulphuric ether, administered two mornings in succession, followed by a third dose on the fourth morning. This causes coughing, and consequent freeing of the tubes of the lame and mucus. Good results have been derived from inhalation of chlorine gas, &c., which acts in the same way. The intratracheal injection of oil of turpentine is said to be followed by favourable results. The system should be supported with as much good nourishing food as possible. S. rafescens, or gordian strongyle (males 5 to 6 inches long, females 6 to 7 inches), is very often associated with S. filaria.
The principal Cestode of ruminants is Txnia expansa, which, when fully mature, is more frequently found in sheep than in cattle. Its body consists of about one thousand segments, each more broad than long. It is the longest of all tapeworms, being (according to Cobbold) in sheep from 8 to 30 feet and in oxen from 40 to 100 feet in length. Its maximum width is inch ; it is found in the large and small intestines. Cobbold thought its larval form was developed in the louse of the ox. The symptoms are emaciation, with dysentery, and loss of appetite. Male fern ought to be given in doses according to the size of the animal. For a full account of the development of Custicercas bovis, the beef measle, see TAPE-WORMS, VOL xxiii. pp. 50.52. C. ovis is supposed by Cobbold to be the larval form of his so-called 7'. tenella of the human subject. Another bladder worm, found only in the mesentery of the sheep, is C. tennieollis, the larval form of 7'. marginata of the dog. Another important hydatid of ruminants is CCe2VILMS eerebralls, which gives rise to gid. ; it is generally found in the brain of sheep, cattle, goats, deer, ke., and also in the soft structures of rabbits. It is the larval form of T. ccenarus of the dog. The symptoms of gid are these. The animal has a rotatory motion ; it does not graze freely ; there is paralysis on the opposite side to the vesicle ; the head is elevated or depressed if the hydatid. is situated in the centre ; and the animal is easily frightened. Medical treatment is of no avail ; but the hydatid may be removed by a surgical operation.
Trichocephalus affinis, the common whip-worm, sometimes gives rise to severe symptoms in ruminants, particularly in sheep. The males and females are each about 2 inches long.
The helminths of the pig, although not very detrimental to the animal itself, are nevertheless of great importance in respect to the Entozoa of the human subject, being the intermediary bearers of some dangerous human parasites in their immature state. Allusion must be made to Trichina spiralis (see PARASITISM, VOL xviii. p. 270). The development of this parasite requires about three weeks after being taken into the stomach, where the capsule is digested ; it then passes into the intestines of the pig, principally the duodenum, where it takes two days to become mature ; then after about a week the embryos leave the body of the female worm, and immediately commence penetrating the walls of the intestines in order to pass into some voluntary muscles. About fourteen days elapse from the time they begin their wandering. Each is generally enveloped in a capsule, but two or even four have been found in one capsule. The male is 1171111, the female ph inch long, and the lame '7th to Ath inch. They have been known to live in their capsules from eighteen months to two years.
Cysticereus cellulose; is the larval forms of Twnia solium of man (see TAPE-WORMS, VOL xxiii. p. 52). " Measly pork " is caused by the presence in the tissues of the pig of this entozoon, which is bladder-like in form. It has also been discovered in the clog, ape, bear, rat, and deer. Other important parasites of the pig are Steplu-ontrus dentatas, or crown-tailed strongyle, and Echinorhynchus gips. This latter is the only thorn-headed or acanthocephaIons worm infesting the domesticated animals (Cobbold).
The commonest of all parasites infesting the dog is Ascaris mystax