LECTURE XXVIII 



INTERNAL PARASITES 



INIany 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 o'eiieral information on th;^ 

 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 jireventable. 



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

 form of the horse gadfly or bot fly, Gastrophiliis intcsiinalis 

 (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 W^ 



about the neck, breast, and fore- ^^ 



rjpj-f^g Fig. 47. — Horse Bot Fly and 



In due time, the eggs hatch and 

 the small larva or bots escape. „„,,•,, e,^„^. L^rva 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, f nally 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, Gastrophiliis nasalis, locates in the horse's 

 nasal chamber. A third species Gastrophiliis hemorrJioidalis 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, ^ledical treatment by the use of carbon bisulphide (6 



141 



