LIVER FLUKE

Poverty Bay Herald, Volume LXIV, Issue 19375, 13 July 1937, Page 11

LIVER FLUKE

EASTERN DISTRICTS BLACK DISEASE BACILLI DRAINAGE OF SWAMPS INFORMATION SOUGHT A new angle on Iho life cycle of liver fluke has been announced by the Department of Agriculture as a result of recent investigation. The lunged snail which lives in swamps is now revealed as the only known host in New Zealand for the fluke. The common black snails which live in stream beds, formerly thought, to be a host are not attacked by larval flukes.

Mr. P. Haugh, veterinary supervisor in Gisborne, mentioned this to-day. lie said that the East Coast of the rJorth Island from Danncvirkc northwards to Tolaga Bay and to a depth of 30 miles inland was the c-hicC fluke bearing region. There was, however, a small infection near Nelson.

"It is in tiicse places,” he said, "that the fluke is responsible for the loss in condition of older sheep through liver disturbance, for the rejection ot livers at the meat works, and for releasing the bacilli of black disease. Black disease, however, has not been reported north of Wairoa. It would bo of interest to know whether any sheep near Poverty Bay have ever shown the symptoms ot' the disease, which are quick death, rapid putrefaction, easy plucking, distension of the belly ancl blackening of the skin. Information on the matter should be sent to the Agricultural Department, Gisborne. Habitat Defined. “During the past six months.” Mr. 1 laugh added, “a reinvestigation of the life cycle of the liver fluke has been undertaken in Hawke’s Bay by the Agriculture Department's veterinary laboratory, Wallaccville. Formerly it was considered that the common black snails of the stream beds were the hosts through which the fluke passed on its way to sheep, cattle and goats, but it is now known that these sharpspired black potamopyrgus living in fast water are not attacked by the larval flukes and do not transmit them to stock.

It tins been observed mierospoieauy that fluke larvae will attempt to burrow into these snails, but soon swim off without making an impression. On the other hand a vigorous and effective attack is made on the lunged snail, myxas ampulla. \Vhich lives essentially iri swamps: and this snail is the only known hosl of the fluke in New Zealand. “By dissecting numbers of specimens of both kinds of snails it has been found that in 5000 specimens of the black stream snail there were 12 species of parasite, belonging to fish, birds and insects, but none of these was the liver fluke. In 2100 specimens of myxas, the swamp snail, there was 2 per cent infection of young liver fluke. That these parasites were the liver fluke was proved by feeding them to laboratory bred rabbits, which in 50 days were found on autopsy to carry mature fluke. Easily Distinguished “The two snails which have been mentioned may easily be distinguished at a glance. Potamopyrgus, the harmless snail, is small in. long), and black, with a sharp spire of six whorls. The opening of the shell can be closed with a bony shutter, and the snail breathes by means of a gill, so that it is constantly submerged. The host of the fluke, myxas, grows as long as 3-Bin., but. it has only three whorls to the shell. The shell is broad, oval and almost globular with the whorls increasing from a minute one at the point to a particularly large third whorl occupying almost, the whole of the shell. Dark grayish brown is the usual colour, though some specimens range to an olive green. There is no operculum to the opening of the shell. “The two genera of water snails are not often found together in one habitat. For potamopyrgus the clean shingle of a stream, or the roots and stems of water cress are the characteristic feeding grounds. The intermediate host of the fluke is found on silty swamp areas derived either from a seepage or from a flat in the course of a stream. The snail lives on the soft fine mud or in the waterholes formed by the trampling of stcok. Usually the bare patches of mud are associated with a growth of the short green marsh rush, juncus lampocarpus, which never grows higher than 9in. The snail is seldom found where the rushes grow very closely, and it lives only 'occasionally amongst the watercress, a plant formerly condemned ns the chief refuge of fluke snails. Combating the Fluke “Juncus swamps formed from black peat or red volcanic ash do ifbt provide breeding grounds for myxas, though these swamps are superficially the same as the yellow, brown and gray muds, which are the dangerous localities. On limestone, sandstone or papa country, fluke swamps are formed. Swamps produced from any of those three rocks with a pumice shower superimposed, are quite ns suitable to the snail. “Since myxas breathes by means of a lung it lives satisfactorily on fairly damp mud for several weeks, blit it is unable to survive long in fast streams and stagnant water. This means that in combating liver fluke, drainage of swamps must be thorough, for a slightly wet patch will retain the snail. * Complete drying for only a few days will kill all snails. Similarly in ap; plying bluestone powder to rid pastures of flukes, if is much more important. that the mud and sill should be covered with the poison than that the water of the slream or spring should Make a. choice in careful test. Seeking ease for throat ami chest.: And when once your choice is made, Let no specious claims persuade. Make a. choice and always heed Thai, iho best: is what you need: And your choice—if choice is free— Woods' Great. tvnpoi-minl Cure will he.

bo impregnated. A bolus of copper sulphate at the head of the stream will be largely wasted as far as destroying fluke snail is concerned. Bluestone kills myxas in extreme dilutions; 301 b. to an acre is sufficient, but the eggs both of the fluke and of the snail are not killed, nor is the young fluke, which may be encysted after leaving the snail on the stems of the rushes ready for the sheep to pick up. Since such encysted fluke live for a year in the shade, it would be at least a year before a pasture could be freed from infection, if draining and poisoning were thorough.