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. — The following treatments have been 

 recommended, but have not had critical test to determine their pre- 

 cise value. An astringent powder which is said to prevent the exten- 

 sion of the trouble and to aid in healing consists of the following: 

 Plaster of Paris, 100 parts ; alum, 20 parts ; naphthalene, 10 parts ; and 

 quinine, 10 parts. The bitter taste of the quinine keeps the animal 

 from biting the sores. 



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

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

 with ether or chloroform and then painting them with collodion has 

 also been recommended. 



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, Trichostrongylus axei, occurs in the lining of the 

 stomach, and is likely to be overlooked unless one is especially on the 

 lookout for it. The worms are very slender and are about one-fifth 

 of an inch or less in length. 



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

 nitely ascertained. There is good reason to believe that its life his- 

 tory 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 re- 

 sults 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. — Because these parasites occur embedded 

 in the lining of the stomach, they injure the stomach wall. Some- 

 times the stomach lining shows areas superficially like a ringworm 

 or a mass of small tumors. (Fig. 5.) In addition to their injuries 

 to the stomach wall, these parasites contribute to the general picture 

 of gross parasitism in horses which is characterized by weakness, 

 paleness of the mucous surfaces, wasting, and digestive disturbances. 



Treatment. — Treatments for the removal of this parasite are sim- 

 ilar to those recommended for the large stomach worms. 



