ANIMAL PARASITES IN THE INTESTINES 159 



embryos form which are ingested by horses with the food. 

 In the intestines they bore into the mucous membrane of 

 the colon and cecum and become encysted. They are 

 frequently found as submucous nodules in the middle of 

 which are the larvae surrounded by pus. Finally the larvae 

 penetrate the capsule into the lumen of the bowel where 

 they reach sexual maturity. 



Treatment. — ^The treatment consists in the use of vermi- 

 fuges as recommended for round worms. Of late atoxyl 

 (grs. v) given in repeated doses once daily has been recom- 

 mended for colts. 



Prevention. — ^As a preventive measure filtering the drink- 

 ing water is advisable. 



Strongylus Contortus. — (See Round Worms in the Stomach 

 of Sheep.) 



Strongylus Convolutus. — This parasite is found in young 

 cattle and calves, also in sheep. It occurs in the abomasum, 

 where, under the epithelial layer of the mucous membrane, 

 it forms gray, pin-head to pea-sized nodules which contain 

 the parasites. If present in large numbers they produce 

 symptoms of gastric disturbance leading to diarrhea, emacia- 

 tion and cachectic hydremia. 



(Esophagostomain the Intestines {Nodule Disease). — The 

 larvae of the oesophagostomum frequently produce disease, 

 especially among cattle and sheep. Inasmuch as the most 

 characteristic lesion on necropsy is the nodule produced 

 by the larvae, the name "nodule disease" has been given 

 to this disorder. The following oesophagostomas occur in 

 domesticated animals: 



(a) (Esophagostomum columbianum of the intestines 

 (American sheep). 



(b) (Esophagostomum radiatum in the intestines. 



(c) CEsophagostomum venulosum of European sheep and 

 goats. 



(d) (Esophagostomum dentatum of the intestines of swine. 

 Life History. — ^The life history of the oesophagostomas, as 



far as is known, is as follows: The ova which are voided 

 with the feces hatch outside of the body. When ingested 

 by an animal during the late summer they pass from the 

 lumen of the intestine into the walls, where they become 



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