LECTURE XXX 



STOMACH WORMS (SHEEP) 



The stomach worm is an especially common and serious para- 

 site of sheep, and this means much, for parasitic diseases of 

 sheep are the serious ones. This parasite is very widespread 

 especially in permanent grass pastures. It affects sheep of all 

 ages and young cattle, but especially 

 lambs. Older sheep showing no symp- 

 toms are the ones usually to blame for 

 spreading the disease. 



The parasite (Hcemonchivs contor- 

 tus) which causes this trouble is a 

 small, threadlike worm, perhaps an 

 inch in length and so slender that it 

 must be looked for carefully or one is 

 liable to miss it. The individual 

 worms are somewhat twisted and are 

 found in the fourth stomach. Fre- 

 quently they are in motion. If they 

 are present in great numbers, the 

 stomach contents near the mucous 

 membrane may seem to be fairly alive 

 and squirming. The worms vary 

 from reddish to dirty white in color. 



Life history. — This parasite is pres- 

 ent in the stomach at all times of the 



Ere. 51. 



year. 



Embryo of Swmonclius 

 contorius coiled on tip of 

 grass blade. Enlarged 100 

 times. (Eansom, B. A. I., 

 Circular 93.) 



The eggs are passed off in the feces, 

 hatch in 14 to 24 hours in warm 

 weather, and reach the ensheathed 

 embryo stage in from ten days to two 



weeks when conditions of temperature and moisture are suit- 

 able. Eggs and newly hatched embryos are very sensitive to 

 freezing or drying, and easily die under these conditions. En- 

 sheathed embryos are very resistant. We cannot depend on 



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