PARASITES AND PARASITIC DISEASES OF HORSES 



9 



Life history (fig. 4.). — The eggs of horse stomach worms have very 

 flexible shells; they are deposited in the lumen of the stomach and 

 are eliminated from the horse's body with the feces. When the eggs 

 are swallowed by maggots of house flies, stable flies, or other flies 

 which breed in horse manure, further development takes place which 

 keeps pace with the development of the maggots. The larvae of 

 Carter's stomach worm of the horse develop for the most part in house 

 flies while those of the small-mouthed stomach worms of the horse 



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 L ^wr/ffs are &y?e//ea* 

 from ffie dyres/yvef ( a ) 

 fracf /y/'/fi? 



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 /ay /T/a/yr eggs: 



/77cr/7i/r-e. 



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 //nagya/s (aj Tfie youry MWvsakyeAp ' 

 ffh /fie /nayfof a/za^/h /Ae/?a/?affija/7d\ 

 are /nfecffye ty/?e/? f/?e aa'u/f 

 y/y (cj erne/yes. 



//orses fiec&/7?e /rr/esfiec/ &&■ 

 a resu/f of ' s-sna/Zotry'/ya 

 /'/7/ec/ec/ yy/e& or- fJre 

 Var/sae- *ts/?/'c/? escape 

 fr-o/77 y//es srA/'/e 

 f/?e /crffer- are fee 

 .0/7 //?e /770/s/ure of/fie'/fts. 



Figure 4. — Life cycle of one of the large stomach worms, Habronema muscae, of 

 the horse. The illustrations of the adult worms are enlarged about 2 times; 

 those of the eggs are enlarged about 150 times. 



have stable flies as their usual intermediate hosts, though they are 

 known to develop also in house flies and other flies. The larvae of the 

 large-mouthed stomach worms of the horse develop in various species 

 of nonbiting flies, including house flies. These larvae attain their full 

 growth in the flies when the latter emerge from the pupae. Horses 

 may become infested with stomach worms as a result of swallowing 

 live, infected flies or infected flies which have been dead a short time 

 and still contain the live larval worms. Another and probably more 

 common way in which horses become infected with these parasites is 

 as follows: As the flies suck the moisture of the lips and nose, the 



811770° — 49 2 



