230 SHEEP : BREEDS AND MANAGEMENT. 



Sheep receive flukes into their system in July, August and 

 September, or the later summer months, and the virulence of 

 the disease depends upon the number of flukes which find 

 their way into the digestive system of the sheep. If few 

 flukes are present no injury may follow, but a number suffi- 

 cient to crowd the bile ducts proves fatal. The subject is 

 full of difficulty, for the degree of mischief depends upon the 

 numbers of the invading parasites. The fluke does not pro- 

 pagate within the sheep, although it lays innumerable eggs, 

 which, with the excrement of the flukes, fill the ducts and 

 cause fatal derangement of the system. It has been ascer- 

 tained that flukes do not multiply within the sheep, and that 

 the severity of the attack depends upon the number of sporo- 

 cysts taken into the body of the sheep. These, when they 

 have attained maturity, lay eggs which are expelled by the 

 flukes in all parts of the bile ducts, in the intestinal canal, and 

 on the soil after escape of the flukes from the body, but 

 wherever they are deposited, their ultimate destination is the 

 soil, to which they are conveyed, either with the faeces as free 

 ova, or in the mature fluke as expelled from the sheep. The 

 infested sheep becomes a bearer and distributor of flukes as he 

 moves from pasture to pasture, expelling ova. As one sheep 

 may contain a thousand flukes, and each fluke forty thousand 

 eggs, it is manifest that one bearer may contaminate a. pasture, 

 though that bearer be in apparent health. 



The cause of fluke disease in sheep is, then, an accumula- 

 tion of encysted larvae in the body of the sheep, which there 

 develop into mature flounders or flukes, capable of laying eggs 

 within the sheep, or without, if expelled from the body. An 

 infested sheep, therefore, is a source of contamination by 

 stocking the pasture with eggs and ova. The flukes are pro- 

 bably for the most part expelled from the host (the sheep) 

 when mature, and when depositing their ova. 



Rain washes the ova into drains, ponds and other accumu- 

 lations of water. The egg contents develop into ciliated 

 embryos which swim about freely in the water. It has the 



