PARASITES AND PARASITIC DISEASES OF HORSES H 



and barns with suitable preparations of these materials offers promise 

 of being the best means of keeping fly populations at a minimum. 

 Sprays having prolonged insectieidal action are obtainable commercial- 

 ly and should be used in accordance with directions accompanying 

 them. 



SUMMER SORES 



A skin disease of horses, known as summer sores and characterized 

 by pronounced skin lesions, is associated in some parts of the world, 

 including the United States, with the larvae of the large stomach 

 worms of horses. The sores may be as small as a millet seed, but 

 are usually about the size of a pea and may attain a size about an 

 inch in diameter. The sores are covered by a soft, brownish-red, 

 pulpy material with cracks or furrows which are filled with pus. 

 In the midst of the softened mass there are small, rounded granu- 

 lations which are firm in texture. 



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 be- 

 come 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 j "or 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- 

 percent solution of formalin, applied by means of a cotton pad which 

 is left on the sores for 2 or 3 hours every day. 



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

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

 summer sores. Flies should be controlled by the use of residual 

 DDT sprays or other preparations of established efficacy. 



THE SMALL STOMACH WORM 



This parasite, Trichostrongylus 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 



