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CIRCULAR 14 8, U. S. DEPARTMENT OF AGRICULTURE 



or Cylicostomum, are usually about a half inch or less in length and 

 grayish white in color, and occur attached to the gut wall or free in 

 the contents of the large intestine of the horse. These worms do not 

 feed on blood, at least ordinarily, but they may feed on the mucosa 

 of the large intestine. The immature forms of some cylicostomes 

 occur in nodules in the wall of the large intestine. 



The small strongyles of the horse contribute to the picture of gross 

 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. 





B 



Figure 19. — Lesions produced by one of the smaller horse strongyles : A, enlarged 

 view of lesion with worms, Triodontophorus tcnuicollis, surrounding it; B, types 

 of lesions. (From Ransom and Hadwen, 1918) 



Treatment. — The treatments recommended for the removal of large 

 strongyles are also used for the removal of small strongyles. Oil of 

 chenopodium and normal butylidene chloride are especially effective 



against these worms. 



Carbon tetrachloride is less effective. 



PINWOBMS 



The pinworms, OxyuAs equL 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 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 



