44 CIRCULAR 14 8, IT. S. DEPARTMENT OF AGRICULTURE 



and hardening of the skin is characteristic of mange, but the most 

 certain diagnosis consists in finding and identifying the mite which 

 causes the disease. In the early stages of psoroptic mange the mites 

 may usually be found in scrapings taken with a blunt-edged knife 

 from around the edges of fresh lesions. In the advanced stages 

 scrapings taken from the edges of scabs or from the bottoms of 

 the folds of skin may contain mites. 



In the early stages psoroptic mange may be distinguished from 

 sarcoptic mange by the character of the lesions and the manner 

 of spreading, but the most dependable diagnosis consists in finding 

 the mite. For practical purposes where facilities for examination 

 are limited the principal differences in form and structure of the 

 two species of mites may be summarized thus: The sarcoptic mite 

 is slightly smaller than the psoroptic mite, and the body of the 

 former is more nearly round than oval. (Fig. 27.) Adults of both 

 species have four pairs of legs, those of the psoroptic mites being 

 long, and all four pairs extend beyond the margin of the body. 

 (Fig. 30.) The sarcoptic mites have shorter legs, and the fourth or 

 hind pair and usually the third pair do not extend beyond the 

 margin of the body. The head of the common scab mite is tapering 

 or cone-shaped and is longer than it is broad, whereas that of the 

 psoroptic variety is bluntly rounded in front and is as broad as 

 it is long. 



It is advisable to examine several specimens in all cases, because 

 under low-power magnifying glasses the females of the two species 

 are more easily distinguished from one another than the males. 

 On account of the burrowing habits of the sarcoptic mites, they are 

 difficult to find, especially in the early stages of the disease. They 

 are situated in burrows under conical papillae, and by scraping the 

 infested area until the blood oozes from the tissue, the mites some- 

 times may be found in the scrapings. 



Contagiousness. — Each species of domesticated animal has its own 

 peculiar variety of psoroptic mange, and the variety which lives on 

 the horse, ass, or 1 mule is not transmissible to other animals, with the 

 possible exception of the camel. The disease is more highly con- 

 tagious to all classes of horses than sarcoptic mange. The predis- 

 posing causes, manner of spreading, carriers of the mites, and pre- 

 cautions to be observed in isolating infected animals and cleaning 

 and disinfecting premises are practically the same as for sarcoptic 

 mange. 



Treatment. — As the psoroptic mites live on the surface of the skin, 

 they are more easily eradicated than the sarcoptic variety. The rem- 

 edies recommended for sarcoptic mange are effective in eradicating 

 this disease. Two dippings from 10 to 12 days apart may usually 

 be depended on to cure ordinary cases. Four or more dippings may 

 be necessary in chronic cases. 



CHORIOPTIC MANGE 

 CHORIOPTIC MANGE MITE 



Chorioptic or symbiotic scabies, commonly known as foot mange, 

 is caused by a mite (Chorioptes equi) which closely resembles the 



