1909.] 



Parasitic Mange in Horses. 



205 



the head project prominent feeding organs, the jaws resem- 

 bling saws. The body is furnished with scales, spines, 

 bristles, &c. The females lay from 15 to 24 eggs at a time, 

 which hatch out into larvae in from four to seven days. These 

 larvae, after moulting several times, develop into adults. The 

 mites can exist on moist dung for several weeks, and for a 

 shorter time on a dry surface. The eggs, it is said, may 

 retain vitality for two to four weeks if moisture is present, 

 but on a dry surface only three to six days. Both mites and 

 eggs are killed in a short period if exposed to a temperature 

 of 104 0 Fahr. or over; but a moderate heat stimulates them, 

 and they become more active. This occurs, for instance, in 

 warm stables or at summer temperatures. 



The three varieties of mange mentioned above are caused by 

 different mites, each of which has a different mode of life. 



The sarcoptes bore into the skin, propagate in the burrows 

 they form, and produce rather severe inflammation of the 

 skin. 



The psoroptes live on the outer surface of the skin, and 

 by means of their mouths and limbs cling to it. These also 

 cause inflammation of the skin by their bites. 



The symbiotes live on the outer scales of the skin, chiefly 

 of the limbs and extremities. 



Sar coptic Mange usually starts on the head, neck, shoulders, 

 or withers, but, according to the method of infection, may 

 start in any part touched by saddlery or harness. The chief 

 symptoms are an intense itching, which is exaggerated in 

 sunshine or when the body is heated, causing the animal to 

 bite and rub the parts. The lesions produced in the skin 

 are in the form of small papules, from which the hair soon 

 falls or is rubbed off, and as the disease spreads scabs are 

 formed. The skin gets thicker, and often shows cracks and 

 wrinkles. Sarcoptic mange is the variety most difficult, to 

 cure, and in old and severe cases treatment must be 

 vigorous. 



Psoroptic Mange.— This variety of mange in horses usually 

 begins on the sheltered parts of the body, as the roots of 

 the mane and tail, but it may spread all over. In a general 

 way it may be said that the inflammation and scab 

 formation on the skin resulting from the bites of the psoroptes 



