PARASITES AND PARASITIC DISEASES OF HORSES 29 
horse. The filarid of the body cavity of the horse is from a little 
over 2 to about 5 inches in length and whitish in appearance and 
usually occurs in the abdominal cavity, but it has also been reported 
from other parts of the horse’s body. Immature forms of this 
filarid, as well as of the closely related filarid of cattle, sometimes 
occur in the eyes of horses as the so-called eye worm or “snake in 
the eye.” 
Life history.—The life history of this worm has not been definitely 
ascertained. From what is known of the life histories of related 
forms, occurring in other animals, it is probable that horse filarids 
are transmitted by blood-sucking insects. 
Symptoms and lesions —The adult worms do not appear to do 
much damage and are not known to be responsible for any definite 
symptoms. When the immature worms get 
into the eye, which apparently occurs only 
rarely in the United States, they produce con- 
siderable irritation and in time may produce 
blindness. 
Treatment.—The presence of this parasite in 
the abdominal cavity is seldom diagnosed dur- 
ing life and no treatment for it is known. 
When the worm is present in the eye, it may 
be removed surgically under local anesthesia. 
Prevention—In the absence of definite 
knowledge concerning the mode of transmis- 
sion of these parasites, no definite control 
measures can be recommended. Measures to 
prevent attacks by biting flies, the prevention 
of fly breeding, and the use of fly repellents are 
indicated as possibly of use, but less on account 
of this parasite than for other reasons. 
BOTS‘ B 
Bot re macoot Soave ; 9) FIcurRE 21.—Threadworms, 
Ss are £20 5 of certain flies (fig. 22) Setaria equina, of the 
known as botflies. Three species of bots abdominal cavity of the 
commonly occur in horses in the United States. pre* Naemmelei, 2 fe 
The common botfly, Gastrophilus intestinalis, 
occurs in practically all parts of the United States. The bots, or 
parasitic larve, are reddish in color and are attached to the white 
covering of the left sac of the stomach or along the ridge between the 
right and left sacs of the stomach. The adult fly deposits its eggs on 
the hairs of the inside of the front legs, breast, mane, belly, and even 
the hind legs. The throat botfly, or chin fly, @. nasalis, is rather 
widely distributed in the United States and is especially common in 
the Rocky Mountain region. The adult fly of this species deposits its 
eggs under the jaw of the horse, and in so doing causes much annoy- 
ance to horses. The bots are yellowish in color and are attached to 
that portion of the stomach which joins the small intestine and also 
to the wall of the upper part of the intestine. The nose fly, G. hemor- 
rhoidalis, has a more limited distribution than the other two species 
and is mostly confined to the North Central States and certain of the 
a eee ee eee ee 
*For more detailed information concerning horse bots and their pr i , 
Farmers’ Bulletin 1503, The Horse Bots and Their Control. PEs Gurwen eo tee 
