THE STATION.

Oamaru Mail, Volume IV, Issue 1033, 12 August 1879, Page 3 (Supplement)

THE STATION.

ROT IX SHEEP. t>eartv twenty years ago. (says the i";ehi), thosts in-i.-i > t siici-p wi re lost in tlreat T'.rit'in from t!:e ravages of tile parasitic whicn is known as rot 7 ; ami in the West of England as "bane" or •• snathe."' i On wet land, excepting only marshes near the sea, rot is constantly present :.nioiv_' sherp which are grazed there ; and m wet fiTiSoiH. when all pasture lands partake more or less of the marshy character, th- disease prevails to an abnormal extent, as it did it in 18G0 and JHt'.l, owing t-> the universal presence of the cheat cause—moisture. Some lands are well known as " rotting-land," and aiucp placed on them for a short time . xhii.it that peculiar tendency to lay on f;ir, which is one of the early signs of the disorder : but after a longer residence on the tainted ground* they snti'er from tile more fnlly developed forms of the affection. attd then"lose tlesh as rapidly as they had previously gained it. Kotting meadows are not objectionable as adjuncts to the lairs in which a butcher may keep the sheep which he intends to slaughter \ but on a sheep farm the smallest piece of ground which possesses the evil reputation is a spot to be avoided, and when discovered, will certainly be fenced off by the tlockmaster. At this time, owing to a considerable rainfall not very prevalent in Ire[an,l according to thelrish Times, it exists, almost as much so as in the great, rotting year 181)0. In various parts of Great Britain the affection also exists to an unusual extent, but not to a degree to excite apprehension. Ilot, perhaps, more than any other wellknown disease of the lower animals, has

yiv.m rise to speculation as to its nature aud causes. According to "Youatt, the literature of the disease is very ancient. Hippocrates gives a good account of it, and our agricultural writers of the earliest times have described the signs of the atFec'ion in terms which leave no rooni for doubting its indentity wit'n tliat which we nre familiar with now*. The most remarkable theories have been indulged in by those who have endeavored to explain the occurrence of rot in certain pastures. Parti,*'d-r irrasses, which grow in marshy situations, were naturally selected as the cause »>f the affect ion by many authorities ; other.-! ascribed some special influence to the irvun or Jew ; aud others have looked to the unnutritious character of the grnssps irrovvn on wet lands, as a sufficient explanation of the debility which is one of the conditions of the advanced form of the disorder.

Before the true character of rot was 'ascertained, it was usual to - sefefc for its causes in the locality where the sheep happened to be feeding when, they mam-

fested symptoms of illness; whereas the animals had probably been infected some time before, when their surroundings were of a totally different character. Notwithstanding the mystery which formerly attached to the disease, everyone who is learned in the history of sheep that rot is due to the presence of flu kes in the liver, and the life history of the parasite contains all that is known on the subject of the causation of rot. Ihe fluke worm (dixtoum hejmticum) belongs to a class of termatode worms, which include many species ami varieties, the role of each being to inhabit the: liver t.ucts of different animals, and thus cause derangement of the digestive functions. To the Danish naturalist Steenstrupp belongs the credit of having thrown the first ray of i;..| lt on the darkness which for a long period had hidden the facts of the development of the worm. In Youatt's time the presence of the fluke in the ducts of the liver was wellknown. and microscopists of that period had detected the eggs of the parasite in l ar( re numbers in the bile j it was even announced that the young flukes just hatched, and not larger than cheesemites, had been found in the liver. This last discovery, however, was purely imaginary, as the researches of Steenstrupp, Siebold, Kuchenmeistei' and others have quite established the fact that the fluke is not at once hatched out from the egg in the organism of the sheep, but has to pass through a series of very remarkable changes, from the condition of the ciliated embryo which the egg produces to that of the mature parasite. Tn the first place, the creature which emerges from the egg of the fluke is destined to become encysted on the shell of a fresh water mollusc, then to be parasitic to one of those soft-bodied animals, and in this condition to be swallowed by the sheep along with the herbage or water. These circumstances explain the fact that marshy places are necessary conditions of the existence of rot, as the water snails, in which the young fluke resides, can only flourish in such situations.

Sheep which feed in such localities where water molluscs abound become the recipients of the inchoate forms of the worpi, which ultimately attains the condition of the mature fluke, and in addition they are exposed to the debilitating effects of the insufficient nutriment afforded to them by the unripe and imperfectly grown herbage of the place. How far the development of rot is favored by the watery food on which the sheep subsist in certain ' • rotting" meadows it is difficult to calculate ; but there is no doubt that the introduction of the flukes in sufficient numbers into the system will in itself cause the disease. ' Under ordinary circumstances, however, the sheep is exposed to both causes of disturbance at the same time, and by.conseqiieuce the progress of the affection is more rapid than it is when the animal, after receiving the fluke larvte, is taken to a drv, healthy pasture and well fed.

Rot is not a contagious disease, not even in the imperfect sense in which sheep scab is contagious ; both diseases are parasitic. But, while scab can be communicated by mere transference of the aoarus from one sheep to another, flukes cannot be transferred directly from a diseased to a healthy sheep ; the eggs of the parasite must be deposited in a favorite situation ; the embryo must find a proper habitat, and then pass through several changes of form, eacli approaching more nearly to the fluke state, until it arrives at the exact point in its development in which it is fit to be introduced into the system of a warmblooded animal.

In the course of the generations through which flukes pass in order to attain full development, the sheep or other animal which becomes infected bythein is merely one of the congenial habitats in which they are required to pass a stage of their existence. While in the liver ducts of the warm-blooded animal, the parasites do not multiply, hut they attain sexual maturity and produce millions of eggs, which, being expelled along with the bile from the alimentary canal of the infected animal, either shrivel up and die, or give exit, to the embryos, according to the nature of the soil and the weather at the time. A rotten sheep, therefore, will be a fruitful source of contamination of land wli'-n the conditions are favorable. It will do no harm at all on high and dry soils, or in hot dry seasons, because in such circumstances the eggs do not advance a stage in development, and probably lose their vitality.