THE ANIMAL PARASITES OF CATTLE. 537 



FLUKES IN LIVER AND LUNGS. 



Two species of flukes occurring in the liver and lungs are known 

 to affect cattle in the United States. These x^arasites are flat leaflike 

 worms; one of them, the common liver fluke {Fasciola hepaticay 

 fig. 24), is less than an inch in length, while the other, the large 

 American fluke {Fasciola mugn-a, fig. 25), is considerably larger 

 when full grown. In their life history these flukes depend on snails 

 as intermediate hosts. At a certain stage of development the young 

 flukes leave the snails, become encysted on stalks of grass (fig. 26), 

 and finally may be swallowed by grazing cattle. Stiles states that 

 " flukes may produce a serious, often fatal, disease, 

 more especially in younger animals. The symp- x^'^'^'^^^x^^ 

 toms are somewhat similar to those produced by 'if _J) 



worms in the stomach. The first symptoms are „, .^, „, 



i _ rif;. 24. — roe com- 



generally overlooked, the disease not attracting at- mon liver fluke 

 tention until the appetite is diminished ; rumination |J^7''^''' "*'''°'' 

 becomes irregular^ the animals become hidebound, 

 and the coat dull and staring. The staring coat is due to the con- 

 traction of the muscles of the hair follicles. The visible mucous mem- 

 branes become pale, eyes become dull, there is running at the eyes, 

 and the animal gradually becomes emaciated. As the disease ad- 

 vances 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 hists from 

 two to five months, wlien the most extreme cases succumb. 



'' Most of the German 

 cattle are said to be in- 

 fested with liver flukes, 

 but even when a large 

 number are present the 

 nourishment of the cattle 

 is not disturbed. Thicken- 

 ing 01 the gall ducts, so p^ 25. — The large American fluke (FaseioZa mayno). 



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 

 comparatively good. It is rare that one sees a generalized edema in 

 slaughtered cattle as a result of fluke invasion, and even in the 

 heaviest infections of young cattle only emaciation is noticed. 



