LECTURE XXVIII 

 INTERNAL PARASITES 



Many kinds of internal parasites seriously affect the various 

 classes of stock. The few selected illustrations used here for 

 the horse and sheep can give only general information on the 

 subject. Space does not permit of detailed information con- 

 cerning even those parasites selected for discussion. Losses in 

 sheep from parasites, internal and external, are especially im- 

 portant, and, as a rule, they are preventable. 



Bots. — The common bot of the horse's stomach is the larva 

 form of the horse gadfly or bot fly, Gastrophilus intestinalis 

 (equi). This fly is commonly observed buzzing around horses in 

 the summer and early fall. It is 

 about the size of a common honey 

 bee. The bot fly reproduces by 

 oval, light yellow eggs, which are 

 attached by the adult fly to hairs 

 about the neck, breast, and fore- 

 arms. Fig. 47. — Horse Bot Fly and 



In due time, the eggs hatch and arva. 



the small larvfp or hnts pqpanp Gastrophilus intesti- 



ine small ^ larvae or Dots escape. nalis equi _ Larva in the third 



Some are licked off, burrow into the stage. 



mucous membrane of the lips for a 



few days, then escape and make their way to the stomach where 



they firmly attach themselves to the lining by small hooks. They 



remain thus in the stomach about 10 months, finally passing off 



with manure. The next, or pupal stage, lasts from four to six 



weeks, and is passed in manure or in the ground. After this 



stage the mature fly appears, ready for the next generation. 



Another species, Gastrophilus nasalis, locates in the horse's 

 nasal chamber. A third species Gastrophilus hemorrhoidalis lo- 

 cates in the rectum, and causing intense itching at times. These 

 parasites may be removed by free rectal injections of 0.5 per 

 cent creolin. 



Bots rarely do any serious harm, although they are very com- 

 mon. Medical treatment by the use of carbon bisulphide (6 



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