THE MORE COMMON AILMENTS OF SHEEP 403 



in proximity to the ground. It is only in the spring time 

 when the larva are well developed that they cause trouble. 

 A discharge is first noticed, which when it first appears is 

 clear and serous, but later it is thick and mucous. More 

 or less sneezing is present, and this is accompanied by a 

 discharge of mucus and in some instances of the larvae. 

 As the trouble advances they frequently turn the head 

 backward and shake it and they rub the nose against the 

 ground. Still later they lift their feet high when walking 

 and go with lowered head accompanied occasionally by 

 staggering. In some instances the breathing is affected, 

 owing to obstructions which arise in the air passages by 

 the presence of the worms, or of the resulting inflamma- 

 tion in the mucous membrane. Appetite fails, a frothy 

 substance runs from the nose, they grit their teeth, con- 

 vulsions follow and death comes usually within a few 

 days of the appearance of the symptoms. In many in- 

 stances the animals may recover, especially in the absence 

 of the later symptoms referred to. 



The life history is in outline as follows : As soon as 

 the young larva are deposited they begin to crawl up- 

 ward into the nostril. When mature the grubs are y^ of 

 an inch long and about 1-3 of an inch wide, and are of a 

 dark color. When mature the larva escapes from the 

 nostril, falls to the ground, bores a hole an inch or two in 

 the same, and in 20 to 60 days emerges as a fly. The 

 period of the development of the larva is about 10 months. 

 In young lambs only young larva are found. The great- 

 est infection is found in sheep two years and over. In 

 ewes the sinuses may hold even more than four or five 

 of the larva, without crowding, and males can hold a 

 number considerably larger. 



Preventive measures, though they involve much 

 labor, are all important. Because of the labor which they 

 involve, they can be best resorted to in the case of small 

 flocks such as are kept on the ordinary farm. One of 

 these is the smearing of the nostrils of the sheep with 



