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 4 



Bots are maggots of certain flies (fig. 22) FiGTOji.-jajgdwo rms, 

 known as botflies. Three species of botflies abdominal cavity of the 

 occur in horses in the United States. 



The common botfly, Gastrophilus intestinalis, 

 occurs in practically all parts of the United States. The bots, or 

 parasitic larvae, 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, G. 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. hem.or- 

 rhoidalis, has a more limited distribution than the other two species 

 and is mostly confined to the North Central States and certain of the 



horse : A, male ; B, fe- 

 male. Natural size 



4 For more detailed information concerning horse bots and their prevention consult 

 Farmers' Bulletin 1503, The Horse Bots and Their Control. 



