ANIMAL PARASITES OF CATTLE. 



525 



Several species of loundworms may occur in the fourth stomach. 

 Two of these are of special importance. 



Fig. 17. — Portion of the wall 

 of the first stomach with 

 conical flukes attached. 



THE TWISTED STOMACH WORM (H^MONCHUS CONTORTUS). 



The twisted stomach worm {HceTnonchus contortus^ figs. 18, 19, 

 20) is sometimes found in enormous numbers in the fourth stomach 

 of cattle. Sheep, goats, and other ruminants may also be infested 

 with it. Among the symptoms caused by 

 this parasite may be mentioned anemia, loss 

 of flesh, general weakness, dullness, capri- 

 cious appetite, excessive thirst, and diar- 

 rhea. The anemic condition is seen in the 

 paleness of the slrin and mucous membranes 

 of the mouth and eye, and in the watery 

 swellings which often develop under the 

 lower jaw (" poverty jaw "). If the fourth 

 stomach of a dead animal is cut open and 

 the contents carefully examined, the para- 

 sites, which are from \ inch to 1^ inches in 

 length and about as thick as an ordinary pin, may be seen, if present 

 in any considerable number, actively wriggling about like little 

 snakes. 



Cattle become infected with these .parasites by grazing on pastures 

 on which infested cattle, sheep, or goats have grazed and scattered 

 their droppings. The worais in the stomach produce a multitude of 

 eggs (fig. 19<7) of microscopic size, which pass out of the body in 

 the feces. In warm weather these eggs hatch in a few hours. If 

 the temperature is below 40° F., they remain 

 dormant, and if below freezing, they soon die. 

 The eggs are also killed by dryness; moisture, 

 on the other hand, favoring their development. 

 The larva? which hatch from the eggs are mi- 

 croscopic in size, and, like the eggs, are, at first 

 and until they have developed to a certain 

 stage, very susceptible to freezing and drying. 

 In ver}'- warm weather the larvae complete their 

 development, so far as they are able to develop outside the body, in 

 two or three days. In cooler weather the time required for this devel- 

 opment is longer, and at temperatures below 70° F. 10 days to several 

 weeks may be necessary. The larvae are then ready to be taken into 

 the body. The eggs and early stages of the larva? apparently do not 

 develop if swallowed, and only the completed larval stage seems to 

 be infectious. In this stage the larvse migrate up grass stalks (fig. 

 20) or other objects, showing activity whenever the air is saturated 



Fio. 18. — Twisted stom- 

 ach worm (Hwmonchus 

 conlortus) . Outlines 

 showing natural size 

 of male (above) and 

 female. 



