TH6 J0UHNAI9 



OF 



^fie department of Agriculture 



OP 



VICTORIA. 



Vol. XV. Part 12. lOth Deeember, 1917. 



FLUKE IN SHEEP. 



(I) STRUCTURE AND I.IFE HISTORY. 



/>)/ (Icorgina iSwi'cl. D.Sc. 

 Structure. 



The comiuoii liver Huke {Fasciola hcpulica), one of the best-known of 

 all parasites, is a flat worm belonging to the group Trematoda. It lives 

 adult in the bile-ducts of the sheep chiefly, also commonly in the ox, and 

 less commonly in rabbits. It has also Ix'cn found occasionally in the 

 goat, hare, and kangaroo, and even in tlie pig and horse, and at times in 

 human beings. 



The parasite is leaf-like in shape, pointed posteriorly, and with a 

 triangidar head end. It has two suckers, one at the extreme anterior 

 end, containing the mouth, the other larger and nou-perforate on the 

 under surface near the base of the head-lobe, and serving as a means of 

 attachment to the walls of the cavity in which it li\(>s. 



The body is yellowish-white to greenish-grey in colour, and is enclosed 

 in a thin, but very resistant, "skin" or cuticle, covered with tiny 

 spines, which are largely responsible for the effects produced by the 

 flukes on the liver of the host. 



The digestive system consists of a strong muscular pharynx or suck- 

 ing-bulb following the mouth, and a much branched and capacious intes- 

 tine, in which the bile, mucus, and blood taken from the host are digested. 

 The reiu'oductive organs of the fluke are hermaphrodite and very com- 

 ])lieatcd. They are admirably adapted for the production, under all 

 cond'tions, of the enormous nundier of eggs^-i)robably many tens of 

 thousands — laid by each fluke. This large nundier of eggs compensates 

 in .some measure for the many chances against any one egg escaping 

 destruction and fully completing its develojunent into a mature in- 

 dividual. 



Life History. 



The eggs are very .small (about ]-lS(Mii ol' nn inc'li long), ovoid, and 

 enclo.sed in hard shells with a lid at one end. Thev are discharged by the 



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