ANIMAL PARASITES IN NOSE AND SINUSES OF HEAD 25 



Life History. — The larvae are deposited by the swift-flying 

 female bot on the margin of the sheep's nostrils, from whence 

 they crawl up into the nasal chambers, cavities of the turbi- 

 nal bones, ethmoid cells and even horn cores. It is possible 

 that the brain is invaded in some cases. They attach them- 

 selves to the mucous membrane to feed and develop. They 

 usually remain in the sheep about ten months, or until the 

 following spring when they leave via nasal passages and 

 reach the ground. In the soil in one or two days they pass 

 into the chrysalis form out of which emerges in six to eight 

 weeks the mature bot fly. The impregnated female, bot 

 seeks sheep herds. She usually hides in cracks and crevices 

 in the sheep barn or on shrubbery or underbrush near the 

 sheep pasture. Sheep try to avoid the attacks of the fly 

 by running away from it with their noses held close to the 

 ground or by grouping themselves in a great mass, their 

 heads toward the centre. If the fly touches the nostril, the 

 sheep will snort, stamp its feet and rub its nose on the fore- 

 legs or ground. They often seek dusty places in the pasture 

 to avoid the fly. Once the "larvae have gotten into the head, 

 however, the sheep become quiet and remain so until the 

 emigration of the parasite begins. 



Symptoms. — If only one or two grubs are present, beyond a 

 slight nasal discharge, the sheep may show no symptoms. 

 When large numbers are in the head, however, the patients 

 show profuse mucopurulent or even bloody nasal discharge, 

 sneezing, snorting, sniffling, shaking the head and rubbing 

 the nose against objects. In severe cases symptoms of 

 vertigo occur, the patient staggering, reeling, and falling 

 to the ground. Sometimes fatal .convulsions are noted. 

 Conjunctivitis may be present. As a rule, however, in 

 about ten days after the first signs appear, and the larvae 

 are expelled, the symptoms subside. 



Diagnosis. — Grub-in-the-head may be confused with sturdy 

 or gid (Coenurus cerebralis). However, in sturdy the older 

 sheep are attacked, there are no nasal symptoms and the 

 forced movements of the patient are more pronounced. Gid 

 is furthermore as yet an uncommon disease in the United 

 States. In doubtful cases a postmortem or the micro- 

 scopic examination of the discharge must decide. 



Digitized by Microsoft® 



