THE ANIMAL PARASITES OF CATTLE. 



513 



ease advances the milk supply is lessened, fever appears, there is 

 generally great thirst, but the appetite almost ceases; edematous 

 swellings appear on the belly, breast, etc. ; diarrhea at first alternates 

 with constipation, but finally becomes continuous. The disease lasts 

 from two to five months, when the most extreme cases succumb. 



"Most of the German cattle are said to be infested with liver flukes, 

 but even when a large number are present the nourishment of the 

 cattle is not disturbed. Thickening of the gall ducts, so that a 

 so-called ' Medusa's head ' forms on the surface of the liver toward 

 the stomach, appears in even well-nourished animals; even in cases 

 of a cirrhosis of the liver it is seldom that any effect upon the cattle's 

 health can be noticed, and so long as a portion of the liver tissue 

 about twice the size of 

 the fist remains intact, 

 the nourishment of the 

 animal may be compar- 

 atively good. It is rare 

 that one sees a gener- 

 alized edema in slaugh- 

 tered cattle as a result of 

 fluke invasion, and even 

 in the heaviest infec- 

 tions of young cattle 

 only emaciation is no- 

 ticed. 



' ' Treatment. — Medic- 

 inal treatment is unsat- 

 isfactory. The disease 

 may be prevented to a 



considerable extent by giving animals plenty of salt, and by intro- 

 ducing carp, frogs, and toads into infected districts; these animals 

 destroy the young stages of the parasite and feed upon the snails 

 which serve as intermediate hosts. " 



TAPEWORM CYSTS OF LIVER AND OTHER VISCERA. 



Three kinds of tapeworm cysts are found in the viscera of cattle. 

 One of these (Multiceps socialis, or Coznurus cerebralis) will be fur- 

 ther referred to in the discussion of gid (p. 515). All of these are 

 the intermediate stages of tapeworms which live when mature in the 

 intestines of dogs, wolves, and other canines. The eggs of the tape- 

 worms are scattered over the fields in the droppings of infested dogs 

 or wolves, and these when swallowed in food or water by cattle hatch 

 out and the embryos migrate to the liver, mesentery, lungs, brain, or 

 other organ, where they develop into cysts, variously known as hyda- 

 tids, bladder worms, water balls, etc. When organs of cattle thus 

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

 to be swallowed and then develop into mature tapeworms. To pre- 

 61386—08 33 



Fig. 23.— Portion of grass stalk bearing three encysted cer- 

 cariae of the common liver fluke {Fasciola hepatica). 



