In respect of treatment we all know that “prevention is better than cure.” Moisture being essential to the growth and development of the fluke-larvæ, it is clear that sheep cannot be infected so long as they remain on high and dry grounds, and even in low pastures they can scarcely take the disease so long as they are folded, and fed on hay, turnips, and fodder procured from drier situations. When once the malady has become fairly developed, internal remedies are of little avail, at least, in view of producing a thorough cure. Palliative treatment may undoubtedly do good, especially in cases where the disease is not very strongly pronounced. The most important thing is the transference of the rot-affected animals to dry ground and good shelter, supplying them, at the same time, with a liberal quantity of manger food, such as beans, peas, and other leguminous seeds. The fodder, of whatever kind, should be frequently changed, and many other hygienic measures adopted, all tending to promote the appetite and general health of the animal. An admixture of salines is a matter of essential importance, especially in cases where the disease is not far advanced. The beneficial effect of salt is one of those few points on which nearly all parties are agreed, and its preservative influence in the case of sheep fed upon salt-water marsh-land has been previously explained. In regard, however, to the legion of remedies which have from time to time been proposed, all I need here say is, that most of them when fairly tested have been found to fail ignominiously. Every year we hear of the adoption, often with enthusiasm, of new so-called specifics, or of ancient medicines whose employment had long fallen into disuse. Thus, for example, in the April number of the ‘Journal des Vétérinaires du Midi’ for 1860, we find M. Raynaud strongly recommending soot, in doses of from one to three spoonfuls, to be followed up by the administration of a grain of lupin for tonic purposes. In like manner, we received from France wonderful accounts of the medicinal virtues of a certain fœtid oleaginous compound, the value of which was put to a fair test by our distinguished veterinarian, Professor Simonds. Having with infinite care and trouble undertaken a series of experiments with the remedy in question, Mr Simonds writes in the ‘Scottish Farmer and Horticulturist’ to the effect that, as a result of his inquiries, he fears “we must conclude that this supposed cure of rot in sheep has proved quite ineffective for good.” The last new “cure” announced is by Mr Robert Fletcher (‘Journ. Nat. Agric. Soc. of Victoria,’ Dec., 1878).
The examination of rotten sheep is not altogether free from danger. Professor Simonds tells us that in August, 1854, “a person of intemperate habits, following the occupation of a country butcher, was employed in skinning and dressing a number of rotten sheep on the premises of a farmer in the county of Norfolk. The sheep were necessarily opened when warm, and while he was so engaged he complained greatly of the sickening smell. The same evening he was attacked with choleraic disease, and two days afterwards was a corpse.” This case is highly instructive and, when taken in connection with the well-known fact that animals affected with the disease putrefy very rapidly, clearly points to the necessity of removing slaughter-houses far away from densely populated localities.
Notwithstanding the above statement, there is little or no danger to be apprehended from the consumption of the flesh of rot-affected animals. On this vexed question we have the strong testimony of the late Dr Rowe, of Australia, who, after leaving the medical profession, became a large and successful stockowner, and devoted himself especially to this question. Dr Rowe, writing from the Goulburn district, said:—“The mere presence of flukes in the viscera of an animal is no proof that it is unfit for human food. For inspectors of slaughter-houses to adopt such a test of wholesome food would be the greatest mistake. It would afford no protection to the public against unhealthy food, would increase the price of animals, and be ruinous to our farmers and graziers. If the consumption of flukey beef and mutton were prejudicial to the health of man, there would be very few people alive in this part of the colony; for, to my certain knowledge, they have had no other animal food to live upon for the last twenty-five years, yet for physical ability I believe they may be favorably compared with the inhabitants of any other part of Australia.” Speaking of his own experiences, Dr Rowe avers that he found the common liver fluke in sheep, cattle, goats, opossums, kangaroos, geese, ducks, and other creatures, but he had never encountered it in men, dogs, or pigs. On the whole I think we may agree with Dr Rowe, in regarding the consumption of the flesh of rot-affected animals as free from danger provided only the meat, be well or even moderately well cooked. It must be borne in mind, however, that an essential objection to its consumption lies in the fact that the watery and otherwise chemically deteriorated flesh is comparatively innutritious. It must also be noted that the meat-supply from fluke-affected animals, as usually sold in the markets, is chiefly derived from animals which have only entered the early stage of the disorder, that is, long before the watery and wasted condition of the muscles has fairly set in.
Respecting the other trematodes I have to observe that Distoma lanceolatum not only infests the liver ducts of cattle and sheep, but also the deer tribe. Its larvæ are likewise supposed to reside in Planorbis marginatus. Still more common and widespread amongst ruminants is the Amphistoma conicum, occupying the paunch. It has been found in the ox, sheep, musk-ox, elk, roe, fallow, red-deer, goat, and dorcas-antelope; also in Cerrus campestris, C. nambi, C. rufus, and C. simplicicornis. Prof. Garrod has also recently shown me examples from the sambu deer of India (C. Aristotelis). Diesing’s A. lunatum, infesting Cerrus dichotomus, is inadmissible. Two other species of Amphistome (A. explanatum, A. crumeniferum) are said to infest the zebu; and I have described another (A. tuberculatum) from the intestines of Indian cattle. An aberrant amphistomatoid entozoon (Gyrocotyle rugosa) has been found in a Cape antelope (A. pygarga). Of more interest, however, is the circumstance that Dr Sonsino has discovered a species of Bilharzia (B. bovis) in Egyptian cattle and in sheep. The eggs of this species are distinctive, being fusiform and narrowed towards either pole.
Comparatively few tapeworms are found in ruminants. Cattle are infested by Tænia expansa and T. denticulata, the former of these two species being also more or less prevalent in sheep, antelopes, and deer. Other alleged species (Tænia fimbriata and T. capræ) appear to me more than doubtful. Unquestionably the common Tænia expansa is capable of giving rise to severe epizoöty among lambs. The privately communicated evidence of Professors Brown and Axe, and published evidence supplied by Messrs Cox and Robertson on this head, are conclusive. Mr George Rugg has also (in a letter to Prof. Simonds, dated Dec. 4th, 1878) communicated the particulars of an outbreak in which “large numbers of lambs perished rapidly” from tapeworms in the intestines, the parasites varying from one to five or six feet in length. This tapeworm (T. expansa) is also very prevalent in Germany. Ruminants, however, both at home and abroad, suffer much more severely from bladder-worms. Of these, Echinococcus veterinorum, Cysticercus tenuicollis, and Cœnurus cerebralis, are not only shared alike by all varieties of cattle, sheep, and goats, but they also infest the deer tribe, antelopes, the giraffe, and even camels. In 1859 I obtained the slender-necked hydatid from a spring-bok (Gazella). Besides these larval cestodes, cattle are very liable to harbor measles (Cysticercus bovis), whilst sheep also entertain an armed Cysticercus (C. ovis). I cannot again dwell at any length upon the source of these immature helminths, but I may remark upon the extreme frequency of measles in Indian cattle. This is explained by the careless habits of the people. They not only consume veal and beef in an imperfectly cooked state, but when suffering from tapeworm no precautions are taken to prevent cattle from having access to the expelled proglottides of Tænia mediocanellata. The subject has already been dealt with in the first part of this work, and also in my ‘Manual,’ quoted in the bibliography. The mutton measle is described under the heading of Tænia tenella. In like manner I must refer to the ‘Manual’ for a detailed account of the gid hydatid (Cœnurus cerebralis). How many kinds of Cœnuri exist it is impossible to say, but I am of opinion that the various polycephalous bladder-worms found by Rose, Baillet, and Alston in rabbits, by myself in a lemur and in a squirrel, and by Engelmeyer in the liver of a cat, are referable to tapeworms specifically distinct from the Tænia cœnurus of the dog.
It was in 1833 that Mr C. B. Rose, formerly of Swaffham, Norfolk, discovered an undoubted example of polycephalous hydatid in the rabbit, the parasite in question bearing a very close resemblance to Cœnurus cerebralis. As the accuracy of Rose’s determination respecting the characters of the hydatid has been called in question, I again invite attention to the original description as recorded in the ‘London Medical Gazette’ for November 9th, 1833. At page 206, vol. xiii, of that periodical, after describing the common Cœnurus cerebralis of the sheep, Rose writes:—“This (i.e. C. cerebralis) is the only species of Cœnurus noticed by authors, but I have met with another. It infests the rabbit, and I have found it situated between the muscles of the loins. It is also met with in the neck and back. This hydatid grows rapidly, and multiplies prodigiously, and being seated near the surface it soon projects, and sometimes forms a tumour of considerable magnitude. When the warrener meets with a rabbit thus affected, he punctures the tumour, squeezes out the fluid, and sends the animal to market with its brethren. I possess a specimen of this species in a pregnant state. The earliest visible state of gestation is a minute spot, more transparent than the surrounding coats of the parent; this enlarges till it projects from the parietes of the maternal vesicle. It continues to enlarge until it becomes a perfect hydatid, attached by a slender peduncle only; even whilst small, other young are seen sprouting from it, and so on in a series of three or four. My specimen exhibits them in every stage of growth, from a minute point to a vesicle the size of a hen’s egg. As I can see no difference in structure between this hydatid and the last-mentioned (i.e. Cœnurus cerebralis), I am unwilling to consider it a different species, for surely a varying locality ought not to constitute a specific character.”
The observations of Rose did not escape the well-known Dutch author, Numan. In a foot-note to his memoir, entitled “Over den veelkop-blaasworm der Hersenen,” he makes the following observations:—“Rose observes that he has found Cœnurus in bladdery rabbits (blaaszieke konijnen) in the skin, and in the cellular tissues of the trunk and extremities. The veterinary surgeon, Engelmeyer, of Burgau, says he has also found the Cœnurus (Veelkop) in the liver of a cat (‘Thierärztliche Wochenschrift van 1850,’ s. 192). These observations differ thus far from those of other writers, according to whom the Cœnurus is only found in the brain and spinal marrow. However, it is not impossible in particular cases that some parasites may have strayed from their ordinary dwelling-places.” Numan seems to have been not a little puzzled to account for these discrepancies, and he was altogether undecided regarding the mode of propagation of Cœnuri and Cysticerci. This will be gathered from the following passage, which I quote in the original:
“Ik moet het onbeslist laten, of de grondbeginsels, waaruit de wormen uit de blaas ontspruiten, als wezenlijke of als zoogenaamde kiemen (gemmæ) zijn te houden, waaromtrent de gevoelens der voornamste Natuuronderzoekers, die zich met de nasporing der blaaswormen hebben onledig gehouden, nog uiteenloopen. Gulliver, door Rose (a. p. pag. 231) aangehaald, houdt ze voor eijeren, in den Cysticercus tenuicollis, en Goodsir, mede aldaar genoemd, spreckt ook van ova bij den Cœnurus cerebralis; doch de laatstgenoemde en Busk houden ze voor gemmæ. Hier wordt voots gewezen op Owen en de meeste onderzoekers van den tegenwoordigen tijd, die het daarvoor houden, dat alle hydatiden zich alleen door gemmæ reproduceren. Rose merkt voorts aan, dat, hetzij men de geboorte dezer ingewandswormen toekenne aan eijeren of kiemen (gemmæ), dit om het even is, wat hunne verspreiding (dissemination) betreft, daar zij ingesloten zijn, waardoor de wijze, hoe zij naar buiten komen en verspried worden, tot dusver een gesloten boek is.”
The idea of Numan that these are strayed forms of Cœnurus cerebralis is not convincing. It must not be forgotten, however, as Leuckart and Numan have both reminded us, that Eichler discovered an hydatid about the size of a goose egg in the subcutaneous tissue of a sheep. This bladder-worm supported nearly two thousand heads. In regard to true hydatids or acephalocysts in ruminants, on which subject I have already dwelt at much length, I may again observe that the Hunterian Museum contains some remarkable examples. In 1854 I obtained Cysticerci from a giraffe, and I have reason to believe that similar bladder-worms infest antelopes and deer.
The nematodes of the ruminants are both numerous in, and destructive to, their bearers, those infesting the lungs being productive of a parasitic bronchitis termed husk or hoose. In cattle the lung-worm (Strongylus micrurus) is particularly fatal to calves, whilst S. filaria attacks sheep, and especially lambs. A larger but less common lung strongyle (S. rufescens) is sometimes found associated with the latter. In 1875 I conducted experiments with the view of finding the intermediate hosts of S. micrurus, and I arrived at the conclusion that the larvæ of this parasite are passively transferred to the digestive organs of earth-worms. The growth and metamorphoses which I witnessed in strongyloid larvæ taken from earth-worms (into which I had previously introduced embryos) were remarkably rapid, and accompanied by ecdysis. The facts were as follows. About the middle of October, 1875, I received from Messrs Farrow, of Durham, a fresh and characteristic specimen of diseased lungs, in which the bronchi were swarming with Filariæ.