256 DISEASES OF ANIMALS. 



WORBIS IN THE HEAD. 



This is probably the most destructive disorder with 

 which sheep are alllicted in this country ; and many die 

 with it, and the owners know not the cause, or learn i! 

 too late. In some cases, half of large flocks have diec 

 of this disease in one year. The annual loss in thi5 

 country is estimated at one million of dollars; but ol 

 late more attention is paid to preventives and cures. 



Cause. A large fly, or bee, (Oestrus ovis,) lays its egg^ 

 in the nostrils of sheep, in August and September, and 

 perhaps earlier and later, where they hatch, and from 

 twenty-five to one hundred small white grubs, Avith 

 black heads, and a black streak on the back, may some- 

 times be found in the cavity between the nostrils and 

 windpipe. They continue in this place till the next 

 summer, when they get their growth, and are as large as 

 a pipe-stem, and nearly an inch long, with four large 

 teeth, as hard as bone. They then leave the sheep, and 

 soon cast ofl" their skin, when the bee appears, and is 

 ready to lay a new lot of eggs. Some say that the 

 worms do not injure fat sheep, as they find sufficient 

 support in the nostrils, but in poor sheep, for want of 

 (bod, they ascend in the head. When attacked by the 

 fly, sheep run with their noses to the ground, and often 

 thrust them into loose earth to shut up the avenues of 

 approach to the enemy. 



Symptoms. They do not generally appear till towards 

 spring, at \viiich time they may be discovered by a sickly 

 countenance and loss of flesh, notwithstanding the best 

 of keeping ; sometimes running at the nose, (though not 

 always,) and snorting, as if trying to blow something 

 from the head. In some cases, the sheep suddenly 

 spring about in a wild, frantic manner, and drop down 

 diead. When this symptom is exhibited, the grubs have 

 assailed some vital part. When they do not die 

 in this manner, they become so poor that their wool 

 stops growing and fills off, and they give little or no 

 milk. Sometimes th->y linger, pining away, and do not 

 die till Ju '.e r July. 



