PARASITIC DISEASES. 171 



4. Stomach Wormci ^^ 



This is one of the most serious ailments that 

 affect sheep, especially is it serious in the young. 



Another member of the Strongyles, the Stron- 

 gylus contortus, a brownish colored thread worm, 

 is the cause of this ailment. 



The life history of this parasite has not been 

 worked out definitely. It is the common sup- 

 position that the ova are voided by in the feces 

 of the infected animals ; other sheep pick them up 

 on the grass or in the water, and thus spread the 

 infection. 



This parasite prefers a cool, damp habitat, 

 and experienced observers have pointed out the 

 fact that the infection is usually acquired around 

 shade trees where the lambs play during the heat 

 of the day. On desert ranges, in sandy or vol- 

 canic ash soil, very little trouble is experienced. 



Symptoms: The experienced eye will easily 

 detect the symptoms of this disease. Along in 

 July or August, the infected animal begins to 

 hang back from the rest of the band. "Off color/' 

 says the herder. Emaciation becomes notice- 

 able, and the walk is hesitating, like a sick person 

 getting out of bed and taking a first few steps. 

 The wool becomes harsh and rough, and the lamb 

 becomes very weak. Later, the victim staggers 

 about, keeping from tumbling on the ground by 

 the greatest of efforts. A swelling comes on the 

 lower jaw, just between the angles of the inferior 

 maxillae, while the visible mucous membranes 

 are pale, and the skin like parchment. Depend- 



