PARASITES AND PARASITIC DISEASES OF HORSES 



29 



digestive disturbances, weakness, emaciation, and anemia resulting 

 from severe infestations with parasites. 



The life histories of the smaller strongyles have not been studied 

 in detail, but the indicated control measures with reference to these 

 worms are the same as those recommended in connection with the 

 control of blood strongyles. 



Treatment. — The treatments recommended for the removal of large 

 strongyles are also used for the removal of small strongyles. 



Figure 20. — Pinworms, Oxyuris equi (females), of the 

 horse. Natural size. 



PINWORMS 



The pinworms, Oxyuris equi, which are commonly seen in horses 

 are the females. These are relatively long, whitish worms with a 

 very long and slender 

 tail (fig. 20). The 

 males are small and in- 

 conspicuous and are sel- 

 dom found. The fe- 

 males may attain a 

 length of 3 to 6 inches. 

 They occur in the large 

 bowel. 



Life history. The 

 gravid females pass out 

 with the manure and 

 then deposit their eggs, 

 instead of depositing 

 them in the bowel. 

 Sometimes the females 

 hang on to the anal 

 opening and extrude 

 their eggs in the region 

 around the anus; the eggs may adhere in this region in the form of 

 yellow crusts. In either case, the eggs develop outside of the body, 

 as do those of the large intestinal roundworm, and in a few days they 

 reach the infection stage. Each egg which develops normally con- 

 tains a small worm within the shell. Ordinarily the eggs do not 

 hatch outside the horse's body. Horses become infested with pin- 

 worms as a result of swallowing the infective eggs in feed or water. 



Symptoms and lesions. The most evident injury produced by pin- 

 worms is the irritation of the anus, which causes a horse to rub its 

 tail and buttocks against any convenient object. This irritation may 

 result from the passage of the worms out of the anus, from the crushing 

 of the female worms as they pass out, or from some irritant property 

 of the eggs. It is also reported that aside from causing this irritation, 

 pinworms are responsible for digestive disturbances, and that, when 

 present in large numbers, they produce anemia. 



Treatment. — Oil of chenopodium, administered as for large stron- 

 gyles, is effective for the removal of pinworms from the horse. Pheno- 

 thiazine also is reasonably effective. Oil of turpentine is also an effec- 

 tive treatment and should be giv^en in a dose of 2 fluid ounces (60 cubic 

 centimeters) for a 1,000-pound animal, immediately preceded or 

 followed by 1 quart of raw linseed oil or by the proper dose of the 



