440 EXTERNAL PARASITES OF ANIMALS 



Sheep. Sheep bot-fly or head-maggot {CEstris ovif^). — The 

 dark brownish parent flics, somewhat larger tlian tlie house-fly, emerge 

 during June and July, and deposit living maggots in the nostrils of sheep. 

 The animals have an instinctive fear of the flies, and are thrown into 

 a panic by their attack. The maggots work their way up the nostril, 

 and find lodgment in the frontal sinuses, where they feed on the 

 mucus. Their presence causes great irritation and the discharge of 

 purulent matter. Sometimes the maggots penetrate into the brain 

 cavity, and death may result. 



Treatment. — It is almost impossible to dislodge the maggots by the 

 injection of any substance, and such treatment is not advised. Never 

 try to extract them with a wire. To prevent the flies from depositing 

 their young, smear the sheep's nose with tar and grease. This is most 

 easily done by placing in the pasture logs in which holes have been 

 bored. Salt is placed in the holes, and the edges smeared with 

 grease and tar. In trying to get the salt the sheep will keep their noses 

 covered with the tar. 



Sheep scab {Psoroptes communis). — The cause of this disease 

 is a minute mite which lives on the skin under a scab or crust and causes 

 the wool to fall out in large irregular patches. The irritation causes 

 intense itching, the sheep become restless, lose in weight and vitality, 

 and in severe cases die. The disease is contagious and may be trans- 

 mitted either directly from animal to animal or by means of infested 

 quarters, cars or pasture fields. 



Treatment. — Dip the infested or suspected animals in some reliable 

 sheep dip at the temperature of about 100° Fahrenheit ; hold the 

 sheep in the liquid two or three minutes, and immerse the head once 

 or twice just before the sheep is released. Soften thick scabs before 

 dipping by wetting with some of the dip and by rubbing with a smooth 

 stick, taking care not to draw blood. Repeat the dipping in ten days 

 or two weeks to kill any mites which may have hatched from eggs since 

 the last treatment. After dipping do not return the sheep to the same 

 field in less than thirty days, to avoid reinfestation. When it is necessary 

 to return the sheep to the same barn or pen, these quarters should be 

 thoroughly cleaned and disinfected with cresol or some other coal-tar 

 dip, used at the rate of one part to 50 parts of water. The addition 

 of whitewash to the disinfectant will serve as a marker and show when 

 the work has been thoroughly done. Avoid introducing the disease 



