ANIMAL PARASITES OF CATTLE. 



529 



numerous, these parasites cause a thickening of the stomach wall and 

 disturb its digestive functions. The symptoms caused by this para- 

 site are very similar to those produced by the twisted stomach worm. 

 The life history of the encysted stomach worm is not known in detail, 

 but it is undoubtedly very much the same as that of the twisted 

 stomach worm. The same 

 measures as recommended 

 above for preventing in- 

 fection with the twisted 

 stomach worm should be 

 used. Medicinal treat- 

 ment would seem to be of 

 little use, owing to the 

 protected position in 

 which the parasite occurs. 



INTESTINAL PARASITES. 



TAPEWORMS. 



Two species of tape- 

 worms (fig. 23) are known 

 to occur in the small in- 

 testine of American cattle. 

 They sometimes grow to a 

 length of several yards 

 and to a breadth of three- 

 fourths of an inch. Small 

 portions of tapeworms, 

 consisting of one or more 

 segments, are occasionally 

 seen in the droppings of 

 infested cattle. The life 

 history is not known, but 

 the infectious stage is un- 

 doubtedly taken in with 

 the feed or water, infec- 

 tion being spread by the eggs of the parasite contained in the feces 

 of infested animals. The eggs are perhaps swallowed by some small 

 creature (an insect, worm, or snail) which acts as an intermediate 

 host, and which when accidentally swallowed by a cow while grazing 

 or drinking carries with it into her stomach the infectious stage of 

 the tapeworm. 



Adult cattle do not seem to suffer much from infestation with 

 tapeworms, but in calves these parasites may cause scouring and 

 emaciation. 



33071°— 16 84 



Fig. 23. — A tapeworm {Moniezia planissima) which 

 infests cattle. 



