ANIMAL PARASITES IN THE INTESTINES 139 



Life History. — The life history of the cesophagostomas, 

 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 

 encysted. They remain in the walls six or seven months 

 undergoing in this time three successive changes. In the 

 early spring the larvae pass back into the bowel lumen and 

 attain full development. In midsummer the females lay 

 their eggs. This applies to all cesophagostoma except the 

 O. dentatum of swine, which is said to mature within the 

 worm nodule in the wall of the intestine. 



Necropsy. — In. sheep and cattle there appear along the 

 course of the small intestine, and often of the cecum, nodules 

 which vary in size from a pin-head to a shoe button or even 

 larger. The nodules vary in color, the smaller being black 

 or gray and the larger grayish-white. On incision they are 

 found to consist of a thick capsule of connective tissue 

 surrounding a greenish-colored, cheesy, or even purulent 

 mass. The small nodules will be found to contain the larvae. 



Symptoms. — Sheep and cattle when feeding upon low-lying 

 pastures, especially during the months of August and 

 September, ingest the larvae. It is also possible that they may 

 become infested in stables. As a rule, if only a few nodules 

 are present no symptoms of disease are produced. On the 

 other hand, if large numbers occur (as many as six thousand 

 have been noted) symptoms of chronic intestinal catarrh, 

 obstinate diarrhea, anemia, emaciation, and cachexia are 

 noted. Nodule disease seems most fatal in pregnant ewes 

 ,on dry feed during the early spring months. As half of the 

 flock can die in two or three months of the invasion the 

 disorder assumes economic importance. 



Diagnosis. — A positive diagnosis can be obtained only 

 from a necropsy. An examination of the feces is of no value, 

 since the ova have not yet been found. 



Treatment. — Medicinal treatment is not successful. How- 

 ever, feeding highly nutritious food, keeping the sheep in 

 small flocks, and less crowding during the winter season, 

 especially among pregnant ewes, are the principal indications 

 to be followed. 



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