TRICHOSTRONGYLIN^ 



271 



Length of female, 12-20 mm. (1/2-3/4 of an inch); male, 10-13 mm. 

 (3/8-1/2 an inch). 



The eggs are oval, 160-200 microns in length by 75-100 microns in 

 breadth. 



The worm is parasitic in the abomasum, rarely the small intestine, 

 of the sheep. It was first collected by Dr. H. T. Marshall and Prof. 

 V. K. Chestnut in Montana. 



4. Trichostrongylus instabilis (Strongylus colubriformis ; St. in- 

 stabilis). Fig. 140. Trichostrongylinas (p. 268).— The body is small, 

 slender, gradually attenuated forward from 

 posterior fifth ; color reddish. Cuticle trans- 

 versely striated ; longitudinal lines and cer- 

 vical papillse absent. The bursa of the 

 male is large and laterally lobed; spicules 

 short, spatulate, and appearing as though 

 twisted. The body of the female is but 

 slightly thinner toward the anus; behind 

 the anus it suddenly narrows to form a 

 sharp tail; vulva near middle of posterior 

 half of the body. 



Length of female, 5-6 mm. (1/4 of 

 inch) ; male, 4-5 mm. (3/16 of an iach). 



The eggs are oval, 73-76 microns 

 length by 40-^3 microns in breadth. 



The worm is parasitic in the duodenmn 

 of sheep and goats of North Africa, Europe, 

 Japan, and United States. In Egypt it 

 has been observed in man. 



Other species which may be found in 

 sheep and goats are Nematodirus filicollis 

 and Cooperia oncophora which are referred 

 to under gastro-intestinal strongylosis of 

 cattle. 



Occurrence. — Gastro-intestinal strongylosis of sheep and goats is 

 generally caused by the presence of Hcemonchus contortus which may 

 be in association with one or more other species. This stomach worm 

 is recognized as one of the most serious of the numerous pests with 

 which the sheep raiser has to contend. Animals of all ages become 

 infected, but the most serious effects are observed in lambs and kids. 

 Occurring mostly in wet marshy districts and in seasons of frequent rain 

 — conditions favorable to the propagation of the lung as well as the 

 gastric worms — the affection is frequently associated with the respiratory 

 form of strongylosis. 



In the United States the stomach worm of sheep, goats, and cattle 



an 



m 



Fig. 140. — Trichostrongylus in- 

 stabilis; male at right, female at 

 left.— * Vulva. xl5. (After Ran- 

 som, Bull. No. 127, Bureau An. 

 Ind., U. S. Dept. Agr.). 



