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 e}^e 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 biting 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) ifte™a^«d worms, 

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

 occur in horses in the United States as fol- Sffi£ : NitSffita?' fe " 

 lows: 



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 

 legs. The throat botfly, or chin fly, G. nasal is, is rather widely dis- 

 tributed 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 annoyance 

 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- 

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

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



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

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



