The Veterinarian.

New Zealand Mail, Issue 994, 20 March 1891, Page 23

The Veterinarian.

PARASITIC DISEASES OF FARM ANIMALS. Parasites in the circulatory system are in most cases larval forms, which enter the vessels on their way to their ultimate destination, and are carried along by the blood stream to the organs •which are their proper habitats. In the horse, larval forms of nematodes are sometimes found in the blood. Most of the worms which have been detected were very minute, and the precise position to which they should be relegated among helminths could not always be defined. The most common laryse in the blood vessels are those of the Sclerostoma armatus, the armed strangle, which has _already been described as-an inhabitant of the caecum and colon of the horse. worms, after obtaining an entrance into the vessels, produce the remarkable effect of inducing aneurismal swellings in some of the larger arteries, especially of the great mesenteric artery. Horses, asses, mules. are, the frequent subjects of this condition, and of the three animals mentioned, the ass seems to be the most susceptible. It might be presumed, from the frequency of the discovery of aneurisms in old animals in various arteries which proceed to the abdominal organs, that the parasites are not injurious to health, notwithstanding the structural changes which they cause in the vessels. Experience, however, shows that the young worms are a source of danger in two directions. First, there is a clear risk of mischief arising from the formation of a clot in the aneurismal sac. This may at once obstruct the circulation and occasion serious derangement, which may be shown by the occurrence of violent attacks of colic; or in the probable event of the clot being broken up, small portions may be carried into the small capillaries, blocking them up and completely arresting the circulation in the part. Derangement of the digestive system or of the circulation in an organ, although it would be indicated by certain symptoms, would not be traced to its true cause, and it is only when the history of the animal daring life is compared with the morbid conditions which are detected on post-mortem examination, that the connection between the two is realised.

A more immediate source of danger is the rupture of the aneurismal sac, and consequent haemorrhage, which may be excessive, and destroy the animal’s life at once, or, when the wound is small may only be attended with bleeding to a sufficient extent to cause pallor of the membrane, feeble pulse, and faintness, from which the animal may recover, at any rate for a time. It is certainly the case that symptoms of internal bleeding in a horse are never attributed to rupture of an aneurism, probably because the disease is never diagnosed during life, indeed, never suspected to exist; and it is not an exaggeration to say that every veterinary surgeon who detects the wellknown signs of internal bleeding at once concludes that the haemorrhage is due to rupture of blood vessels in the liver.Besides the danger of serious or even

fatal bleeding from rupture of an aneurismal sac, there is some risk of perforation of the walls of the vessels by the wandering armed strangles without the occurrence of aneurism ; this danger, however, is comparatively slight. Among the parasites found in the blood of the horse the most remarkable is the monad, which is known in India as the surra parasite, the disease with which the creature is associated being termed surra, or pernicious .anaemia. The affection was at first considered to be analagous to relapsing fever of man, and the parasite was looked upon as identical with the spirillum which is found in the blood in that disease. Careful microscopic inspection soon demonstrated that the monad of surra is not the least like the spiral threadlike organism, the-spirillum, but, on the contrary, it has a body somewhat irregular iri'form, but generally oval, arid possesses a flagellum at each end, by the aid of which its violent and rapid movements are performed. No satisfactory evidence of the influence or the surra parasite in the production of the disease has been advanced. It is quite certain, however, that the same parasite—or, at least,. an identical organism so far. as form is concex’ned is found in the blood of a large proportion of the common sewer rafc3 in this country. "Very little doubt exists as to the occasional presence in the blood of wandering larval nematode worms. The fluid is not generally considered to be the home of parasites, and the helminthologist rarely thinks of searching for them in the interior of blood vessels. Among ruminants in this country no blood parasites have been found ; but in cattle in Africa, and also in India, a very curious form of fluke has been found. The parasite is distinguished from other nematodes by the separation of the sexes. The worm was discovered by Bilharz in 1851 in the human subject in Egypt. A similar worm was found in 1876 by Sonsin in the portal vein of a bull in Egypt. It is said to cause a disease which is possibly mistaken for cattle plague. The parasite is unknown in this country. Dogs in many parts of the world are victims to the ravages of a nematode, which is distinguished by the title of the cruel strangle (Filaria immitis). A specimen of a dog’s heart was sent, to The Field office in 1872, ’ stuffed with the adult worms, some of which attain a length of more than a foot. Commonly these parasites are found in native Chinese dogs in the cavities of the heart, when the animals have not in life given any indications of their presence In other cases death is the result of their invasion, sometimes suddenly the dog falling down in a fit, in other cases showing signs of distress for some days previously. It has not been observed that the embryos of the worm in the blood cause any inconvenience. Other nematodes than the one above described have been found in the heart of the dog by different helminthologists. Strongylus vasosum, a small thread worm about an inch in length, was seen by Dujardin in. 1843 in Paris, in the heart of. a dog which had died suddenly. The worms were clustered together in masses in the right

ventricle and auricle, and seemed to block up the opening of the pulmonaiy artery. Since then the worm has been met with frequently in France and Italy. . ~ . Sfcrongylus sublatus is another variety of small thread worm, which was found by Leisering in the venus blood of two dogs in considerable numbers; each drop of blood examined contained from four to six specimens. Treatment of the several forms of parasites in the blood cannot, be said to have been placed on any satisfactory basis. In the first place, the parasites are rarely detected, or even suspected to exist, until they are found on postmortem examination, and if they were, there is no medicine which could be relied on to destroy them in the blood stream, and it may be doubted whether a multitude of dead parasites in the circulating fluid would not be moie obj ectionable than the living worms.