PARASITES AND PARASITIC DISEASES OF HORSES 9 
pups. 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 possibly 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 larve, 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 
Z 
Ree tall Bes 
(y(’ 
S7IQIIUFE. 
The (7a@titre 
BOTTAS 117 Fhe Sorta 
lap 17700 EFGE. 
lhe eggs are swallowed Ly fly 
l10GG018 (a) (he young wort avelep 
Wt the maggot and tn the pupa lb) and 
are infective wher the adu/7 
Sly (€) errerges. 
Horses becoine yifested aF 
aresul? Of strallowir 
“pected flies or the 67 
Sorvae which escape “ee 
Jrom flies wile 
the latter are feeding 
on the mosture of the lips. 
FIGURD 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 larvee 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 
153249°—33——_2 
