PARASITES AND PARASITIC DISEASES OF HORSE® 



27 



parasitism, and together with the large strongyles, are responsible for 

 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. 



PINWORMS 



The pinworms, Oxijuris 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 

 inconspicuous and are seldom found. The females 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 de- 

 positing them in the 

 b o w e 1. 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 in- 

 testinal roundworm, 

 and in a few days 

 they reach the infec- 

 tive stage. Each egg which develops normally contains a small worm 

 within the -shell. Ordinarily the eggs do not hatch outside the horse's 

 body. Horses become infested with pinworms as a result of swallow- 

 ing 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. Oil of 

 turpentine is also an effective treatment and should be given in a dose of 



Figure 20. 



Pinworms, Oxyuris equi (females), of the 

 horse. Natural size 



