PARASITES AND PARASITIC DISEASES OF HORSES 11 



This disease has been studied in Europe, Africa, and elsewhere, 

 where it has been noted that its seasonal occurrence corresponds to 

 the prevalence of flies. It is unlikely that the worm larvae invade 

 the unbroken skin, but it appears to be well established that when a 

 horse's skin is broken by some injury and when flies which carry 

 the worm larvae feed on the sores, the larvae escape from the mouth 

 parts of the fly and live for a time in the wounds. These larvae irri- 

 tate the sore, so that instead of healing as a simple sore it may 

 become a more or less chronic thing which does not heal until after 

 the occurrence of frost in the fall. 



Although conditions known as " summer sores " in horses are 

 known to occur in the United States, the disease has not been exten- 

 sively studied here and the relation of stomach-worm larvae to sum- 

 mer sores still needs further investigation in this country. Recently 

 the occurrence of the larval worms from summer sores in horses in 

 the United States has been definitely reported. 



Treatment for summer sores. — An astringent powder which is said 

 to prevent the extension of the trouble and to aid in healing consists 

 of the following : Plaster of Paris, 100 parts ; alum, 20 parts ; naph- 

 thalene, 10 parts ; and quinine, 10 parts. 



Good results are reported from the use of a caustic paste composed 

 of arsenious oxide, 1 part, and flour, 5 parts. Washing the sores with 

 ether or chloroform and then painting them with collodion has also 

 been recommended. Some veterinarians prefer the use of a 5 to 10 

 per cent solution of formalin, applied by means of a cotton pad 

 which is left on the sores for two to three hours every day. 



Prevention. — Skin injuries should be protected from flies by the 

 use of pine-tar oil or other means to prevent their conversion into 

 summer sores. 



THE SMALL STOMACH WORM 



This parasite, T 'rich os iron gylus axei, occurs in the lining of the 

 stomach, and is likely to be overlooked as the worms are very slender 

 and only about one-fifth of an inch or less in length. 



Life history. — The life history of this parasite has not been defi- 

 nitely ascertained. In a general way its life history is similar to 

 that of blood strongyles, described elsewhere in this circular, with 

 respect to the development of the eggs and larvae on pastures. It is 

 also fairly certain that infestation is direct, and results from the 

 swallowing, by horses, of the infective larvae with food or water. 

 However, these worms burrow only into the stomach wall and are 

 not known to wander extensively, as young worms, throughout the 

 body of the horse. 



Symptoms and lesions. — These parasites injure the stomach wall. 

 Sometimes the stomach lining shows areas superficially like a ring- 

 worm or a mass of small tumors. (Fig. 5.) In addition to these 

 injuries, the parasites contribute to general gross parasitism in 

 horses which is characterized by weakness, paleness of the mucous 

 surfaces, wasting, and digestive disturbances. 



Treatment. — Treatment for the removal of this parasite is similar 

 to that recommended for the large stomach worms. However, this 

 treatment has not had critical test to determine its exact efficacy 

 against the small stomach worm. 



