PARASITES IN OUR DOMESTIC ANIMALS.

Bruce Herald, Volume VI, Issue 380, 16 August 1871, Page 7

PARASITES IN OUR DOMESTIC ANIMALS.

Some commotion appears to have been caused of late amongst scientific men in England owing to the accounts given by Dr Cobbold in his lecture at the Society of Arts on ■' Our Food-producing Ruminants and the Parasites which reside in them," in the course of which be treated of the breaking out of a disease known as Trichiniasis. The subject of parasites and f he inconveniences we derive from them is bv no means a pleasant one to think about, and yet familiarity with their habits and hiding-places is necessary to enable us to guard against- them. For a long p r oil of time, scientific men have been thoroughly conversant with the apnearanc. of trichina in the pig, and with the fait that from eating uncooked pork this parasite has been transferred to the human subject in France, Germany, and elsewhere on the Continent of Europe. But it was not until Dr Cobbold delivered the lecture above referred to that the disease was known to have made its appearance in England. The human subject derives the trichinae principally from the pig, into which they are intrcducni in the form o l egg-like cysts These cysts find their way into the stomach and intestines of the animal, and there they develops into forms, which in turn become the producers of vast quantities of eggs ; from these art* hatched minute creatures, armed with spines, with which they pierce the mucous membrane of the alimentary canal. They penetrate the tissues, and are conveyed through the larger vessels by the blood current, until they reach the muscular structures, where they find a favorable nidus for their further development. Thus it is that meat infected with trichinee when used as food, produces

tli- parasite in the human subject. We ■acquire, ihe trichinae in the form of an fn^ystic muscle worm, and the pip: is the animal which mostiy gives us the eggs and emltryos of its entozoa. A temperature of 17Odeg\ Fahrenheit is requisite to destroy the trichinoe, and as meat, when roasting 1 , seldom reaches this temperature at the centre, it is evident that hadly-cooked meat muse produce ill effects. Trichinae are by no means the only parasites of common occurrence in our domestic animals ; among- the others may be mentioned a few species of tapeworms or toenice. These are more common amongst men, dogs, and other carnivora, than in horses, and such like vegetable feeders. They appear .to be developed especially from the eating- of meat, either in a raw state or imperfectly cooked. The teenia solium of man is produced by eating 1 meat infected with cysticereus cellulosce, or the measles, as this disease is termed. It was not until the researches of Von Siebold and Kitchen meister that British physicians ascertained the frequent occurrence of parasites in pig's, which, on reaching 1 tha human intestine, develope into tasnias. Measles is a purely parasitic disease, produced by the introduction into the eystam of the pig- of the mature or fecundated ova of tenseia solium. The process of their development has been carefully watched by many observers. The embryos of the tapeworm are globular, and armed with sharp-pointed appendages, with which they burrow through the mucous membrane of the intestine, thus finding their way into the larger blood-vessels, and so, by means of the circulation, they reach their destination in the muscular structures. These embryos cannot find their way through the tissues of adult animals, and thus the fact that hydatids appear as a rule only in pigs under a year old is accounted for. Cysticerci have no means of escape, and therefore they remain in the muscular structures until the natural term of the pig's existence is at an end, and then they pass into the bodies of human beings. According to Leuchart the average life of a tapeworm is two years. ft produces in that time 1600 joints, and each of these joints contains a large quantity of eggs. Every eg^ is capable of developing into a cysticercus, but fortunately the great majority of tapeworms are destroyed, or we should soon have all our pigs suffering from cysticercus cellulo?os. Measles in Cattle : Accoidingto the researches of Dr Leuchart, another form of tapeworm is not unfrequently confounded with the tcenia solium, which is produced in man irom eating imperfectly-cooked veal and beef, and not by eating measlv pork. A hydutid prevails amongst cattle in many parts of the <vorld, which develops into titinia mfidiocanellata in the human intestines. Dr L; j uchart has succeeded in producing measles in the. calf by feeding it with joints of the tapeworm. Another very common parasite is the toe.nia crenurus of the dog, which, when taken into the system of the she«p, produces 1 the very common disease known as sturdy, or caenurus cerebral!*, in that animal. This may be easily demonstrated by giving the ova of the dog's (apeworm to a lamb. Symptoms of the disease show themselves usually from a fortnght to three weeks offer the proglot tides have been swallowed, but this varies with the tiino the joints have been exposed to the air and moisture. Sturdy seldom affects sheep above two } r ears old, and is most common in. sheep under one yeai* old. It manifests ihself in a vfu-,<Sty of WJiVS, (U--pendenc entirely upon the number and situation of the hydatids. The most common form of the disease depends on the presence of a hydatid in one of the hemispheres of i he cerebrum, or brain proper. The sheep turns to the right or left according to the hemisphere effected. Two other tapeworms are worthy of passing 1 note, viz., tasnia echinococcus of the dog, the hydatid of which is found both in man and animals ; and '.he tsenisi marjjinataof'the same animal; the hydatid forua is the cysticercus tenuicollis of the sheep and pig. A very important question has thus arisen : — Does the system now so much adapted of sewage farming tend to disseminate the eggs and other parasitic pmbrvos, and thus render their appearance in man and our domestic animals more frequent than it used to be ? Dr Cobbold considers this to be an open question with regard to trichinae, and that the probability is, that it is not due to sewage farming 1 that this parasite has recently made its appearance in England. But, on the other hand, t'lere appears to be every reason to believe, that the eg«.'.s of the tapeworm foenias are conveyed in the sewage, and become attached to the blades of grass and other herbage carried off from the farm for the consumption of cattle and sheep, and thus die embryos are introduced into the systems of the domestic animals and become developed within tli^m