PARASITES AND PARASITIC DISEASES OF HORSES 9 
pup. 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 larvee, which are present in the 
mouth parts of the insects, escape, the heat and moisture of the 
horse’s body stimulating the larve to wriggle out of the flies. Once 
TE €995 COMIMaMIIG YOUNG, 
worms are expel/ed 
Yrom the digestive / (a) 
track wit 
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The 17a@+tlre 
Worms 17 The Storiath 
lap 17101 EGGS. 
lhe eggs are swallowed by fly 
WHNAG907S (a) he young worms avelop 
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are infective wher the adiu/7 
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Horses become tifested as / 
aresul? of swallowia ph ae 
“pected files or Be Cy i) 
Sorvae which escape ~te 
Jrom flies while 
the latter are feeding 
on the mosture of the lips: 
4 
Ficurn 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. 
the larve are on the lips they are readily swallowed. Those larve 
which get into the nasal’ cavities probably wriggle into the pharynx 
and are also swallowed. When the larve reach the stomach they 
are in their normal location where they settle down and develop to 
maturity. It is possible that the small-mouthed stomach worm is 
transmitted by the bite of the stable fly. 
Symptoms and lesions —No definite symptoms which indicate the 
presence of these parasites in the stomach are known. The worms 
are injurious because of their tendency to attach themselves to and to 
penetrate into the stomach wall and, in the case of the large-mouthed 
13423 (———e 
