ANIMAL PARASITES OF CATTLE. 



533 



and the embryos migrate to the liver, mesentery, hings, brain, or 

 other organs, where they develop into cysts, variously known as 

 hydatids, bladder w^orms, water balls, etc. When organs of cattle 

 thus infested are eaten by dogs or wolves the cystic worms are also 

 liable to be swallowed and then develop into mature tapeworms. To 

 prevent cattle from infection with these parasites stray dogs, wolves, 

 and coyotes should be killed wherever found, and dogs too valuable to 

 kill should be kept free from tapeworms. As a precaution against 

 infection with tapeworms, the viscera of cattle, sheep, or hogs should 

 not be fed to dogs unless cooked. 



Hydatids {Echinococcus granulosus) form tumors (fig. 27) of 

 varying size (sometimes as large as 6 inches in diameter) in the 



Fig. 27. — Hydatids {Echinococcus granulosus) in portion of hog's liver. 



liver, lungs, and other organs. Their contents are liquid, resembling 

 water. The presence of these parasites can not be detected in the 

 living animal and there is no medicinal treatment for them. Or- 

 gans containing hydatids should be destroyed by burning in order to 

 prevent their being e^ten by dogs. This is especially important, as 

 dogs infested with the tapeworm stage of this parasite are a menace 

 to human beings on account of the danger of infecting them with 

 hydatids, which develop in man if the eggs of the hydatid tapeworm 

 are swallowed. 



Thin-necked bladder worms {Taenia hydatigena^ fig. 28) are most 

 commonly found attached to the mesentery and omentum. There is 

 no medicinal treatment. 



GiD. — Bladder worms {MuUiceps m/uUiceps, or Cmnurus cerehralis) , 

 which are occasionally found in the brain of cattle and cause gid. 



