Agricultural and Pastoral.

Otago Witness, Issue 571, 8 November 1862, Page 6

Agricultural and Pastoral.

THE ROT IN SHEEP.

(From the Me rival Times and Gazette.)

Epizootic diseases are only of less interest to the practitioner of medicine tiian epidemic. Especially is tlfis true of diseases nflecfinsr those oi the donifsticated animals which farni^h human food. The terrible prevalence of " rot " ainonjist sheep in 1860, which swept off whole flocks in the western and southern counties of England, and extended to several of the eastern and mid land, has been the immediate occasion of the publication by Professor J. B. Simouds ot an able pamp'ilet on the subject, which emborlies the results of an investigation originally made at the the Royal Agricultural Society. The cause ot "rot" is now generally admitted to be the presence of the " liver fluke " (Distoma heputicum) within the biliary duets. The nuturaUiiatory ol the distoma is not yet entirely made ouc. The following facts, however, seem tolerably certain ; Each of the innumerable ova of the fluke gives origin to a certain number of ciliated circular embryos. The maturation of the cmbryosyiind their escape from the ova, appear from some experiments of Mr Simonds to take place more rapidly when the ova are kept damp only, with free exposure to air — the circumstances afforded In location in a wet pasture— than when they are allowed to remain covered with water. No change seems to take place in the embryos until they become para:-itic to water-snails, slugs, &c Located in these creatures, they become converted iuta a peculiar organism called a ccr-caria-sac. From the nucleus of the distomaembryo within the cercaria-sac a brood of young cereariae — little tailed worms, so called from their caudate form — are formed by a process of successive budding, each one in turn becoming parent, From the fir.^t, second, or third of these offspring a return to the original form of the distoma takes place. The cerearia resembles the distomn, except that it has no sexual organs. In order that the higher degree of development ind.cated by the presence of ovaries and testesshould take place, it is necessary that the cercarias, after being set from the cereaii.i-sac, should become eutnzoic. Some varieties of cereaiii havi been observed by Nitzsch, Siebold, and others, to bore their way into water-snails, to case oft their tails, aud develop into flukes with perfect sexuu 1 organs. Embedded in the body of tlu snail, >eforc the change into the fluke, the cci - caria i assed into the pupa state, by rolling itselt up intD a ball, and emitting from the surface oi its body a quantity of mucus which hardens into a shell Mice cnvcriner. The pupa state has been observed by Steenstrup to continue in some instanuts tor many inoiuils ; it is the penultimati sta-'e in the series of transformations which result in the development of the perfect fluke, and it appears probable that it is only when entering tne organism of vertebrate animals in the pupa stage of the cercaria that tho entosoon will b«" further developed. Ten years ago, Mr Simond.administered a large quantity of tiie ova of tin distoma to a sheep, but on killing the unimal six months afterwards, and examining the liver and f '°- organs, not ix single fluke was found * t oilar ex jerin €n s have been made by Gerlach u-^ with a similar leoult. The tailed free living form of cprcaria has also been administered b\ De la Valctte, but no substqueut metamorphosis into the distoma took place. On the other hand, when given in the pupa state they quickh become provided with geim-stoek, testes, anil ovaries; in fact, become converted into flakes. The reason of the /reat liability of the ruminant animals to become the residence of distomata, M Simonds attributes to the fact that the encysted cercarke aie not at once liable to be destroyed b\ the action of the gastric juice, but are detained lor an indefinite length of time within the iiimei. and the other preparatory stomachs. That sheep are especially the subjects of the disease is probably explained by their feeding close to tin g ound, cropping the short grass where the pcnulumate forms of the distoma abound. A curious fact confirmatory of this view is related by Cleevc, in an essay on " Diseases of Sheep." In a Devonshire patish all the sheep depastured in the marshes were attacked with " rot " and died, wiili the exception of four. These four were all " hogjawed," that is, the lower jaw was shorter than the upper ; they consequently could not bite rear the ground. The prevention of" rot' 5 appears to resolve itself into complete v d rdraining — iUat is, getting rid oi water ntc(.-i.».iry to the development of the cercaria?. Mr Simonds instances the grass land of Middlesex in the socalled Harrow district, where the surface-soil rests immediately on the London ciay, and where there is a great want of under-draining, as enormously lessened in value by the persistence of'the " rot." Large and profitable sheep cannot be fed there; the meadows are stocked with Welsh and other mountain breeds of little value. Gracing in saltwater marshes is likewise a preventive, but not a cure, when perfected distomata are present in the biliary ducts. Saltwater is destructive of the cercariae, but diet will exercise but little influence on the perfected entozea. It is,a feet worth noticing that persons are sometimes seriously affected by the effluvium rising from the carcases of rotten sheep. Mr Simonds mentions the case of a butcher of intempei ate habits who was seized with choleraic symptoms and died, apparently in consequence of skinniHg and dressing a number of sheep affected with the disease. The sheep were opened warm, and while engaged in preparing tre-n he complained greatly of the sickening smell, 'the post-mortem appearances present in a sheep which has died of "rot " are great emaciation and general pallor of the tissues, a harshness and dryness of the wool, which pulls easily from its follicles; a soft, flabby state of the muscles; infiltration of the areola tissue with watery fluid, which is apt to accumulate about the front and lowepijarts of the neck and around the lower jaw ; ascites ; effusions of scum taking the place oftheomental and supra-renal fat ; condensation of the structure of the liver, which assumes a pale or dirty yellow color, not unfrequentlv speckled or mottled with red ; thickening and calcaieotis disposieion in the coats of the biliary duets, which are commonly dilated ; oistomata in varying numbeis, and ova within the ducts; and lastly, general anaemia of the vital organs. We have only space to notice two other curous points with regard to the distomata. There seems reason to believe that, like some other internal parasites, on the death of the animal in whose body they are located, they quit their position, as if attempting to "escape, _ Another fact, is that dead flukes •Dtnetinies form the nuclei of biliary calculi. We may refer such of our readers who'wish for information on the structure of these entozoa, and their distribution in the animal kingdom, to an excellent paper ■' On Flukes, 1 ' by Dr. T. Spencer Cobbold; published in the first number of the Intellectual Observer. The whole subject of the genetic cycle ot' the parasite's existence, together with the common and destructive epizootic disease which it originates, presents so mai y point* of interest to the pathologist, no less tha.. to the comparative physiologist and naturalist, that we think no apology necessary for having thus submitted it to our readers' attention.