612 



SCABIES — SCAB — MANGE. 



the eyelids, and is very rare. It is produced by the Demodex folUcu- 

 loruni var. ovis. 



SARCOPTIC SCA'BIES. 



This scabies has long been recognised as affecting more especially 

 the head, muzzle, etc. It was mentioned as long ago as the fourteenth 

 century by Jehan de Brie, but, until Delafond's time, no one recognised 

 that it was caused by an acarus. In 1858 Delafond discovered the 

 parasite in Piedmont sheep. 



Causation. Formerly, writers on the subject and shepherds attri- 

 buted this disease to the wounds and excoriations which sheep receive 

 in passing through brambles, holly, etc., or in rubbing against their 



racks. The true cause of the disease 

 is the presence under the skin of the 

 Sarcoptes scahei var. ovis, which passes 

 from sheep to sheep by direct con- 

 tact. The animals attempt to rub 

 against everything about them, even 

 against their neighbours. These para- 

 sites can be transferred from the goat 

 to the sheep, and rice versa. 



Walraff, Roloff, Delafond, Gerlach 

 and Railliet have described cases of in- 

 fection in man, but the disease is rarely 

 more than of a temporary character. 



Symptoms. This form of scabies 

 affects the head and the parts free 

 from wool. 



At first the parasites invade the 

 upper lip and the tissues about the 

 nostrils, sometimes, but more rarely, 

 the eyes and ears. They cause the 

 formation of vesicular papules, ac- 

 companied by violent itching. The 

 animal, in rubbing itself, excoriates these papules, which discharge a 

 fluid and soon .become covered with yellowish-brown crusts. 



The disease afterwards invades the face, forehead, jaws, and entire 

 head. The skin becomes wrinkled and the brownish crusts thicker 

 and more abundant. These are fissured and bleeding, and they give 

 the face the appearance of one vast sore. 



The parasite rarely attacks the region of the elbow, the belly, or 

 the inside of the thigh. The disease never advances in parts covered 

 by wool, although in breeds of sheep with thick wool, such as are found 



Fig. 251. — Sarcoptis, magnified 100 

 diameters. (After Kailliet.) 



