PARASITES AND PARASITIC DISEASES OF HORSES 



39 



nostrils must be kept away from the gas. A concentration of about 

 1 per cent sulphur dioxide is necessary to kill the parasites, and serious 

 injury or death may result if the gas comes in contact with the eyes 

 or nostrils. After fumigation it is necessary to hand treat that part 

 of the head that was not fumigated. (Fig. 26.) 



HORSE MANGE 



Scabies in horses, commonly known as mange, itch, or scab, is a 

 name given to a group of contagious skin diseases caused by minute 

 parasites known as mites, which live on or in the skin. Four species 

 of these parasites are found on do- 

 mesticated animals, but horses are 

 commonly affected by only three of 

 them. These parasites are clas- 

 sified zoologically in three different 

 genera — Sarcoptes, Psoroptes, and 

 Chorioptes. Mites of the first two 

 genera are shown in Figures 27 

 and 30. 



In obtaining their food from the 

 host and preparing a resting place 

 in or on the tissues, the mites cause 

 wounds or lesions in the skin. As 

 each kind of mite possesses distinc- 

 tive habits, the location and nature 

 of the lesions in the early stages are 

 more or less characteristic. Each 

 kind of mite, therefore, causes a spe- 

 cific kind of mange which is named 

 after the generic name of the mite. 

 Thus we have in horses sarcoptic, 

 psoroptic, and chorioptic mange. 

 The sarcoptic variety is the one most common on horses in the United 

 States. 



Figure 27. — Sarcoptic mange mite. 

 Female. (Magnified 100 times) 



SARCOPTIC MANGE 



SARCOPTIC MANGE MITE 



The mites which cause sarcoptic or common mange of horses are 

 small, white, or yellowish parasites known technically as Sarcoptes 

 scabiei equi. (Fig. 27.) The female when full grown measures about 

 one-fiftieth and the male about one-sixtieth of an inch in length. When 

 placed on a dark background they are visible to the naked eye. The 

 general form of the body is more nearly round than oval, and the 

 bluntly rounded head is as broad as it is long. When mature, these 

 mites have four pairs of short, thick legs, the fourth pair and usually 

 the third pair also not extending beyond the margin of the body. 

 Under a high-power miscroscope a number of short, backward-project- 

 ing spines may be seen on the upper surface of the body. 



The sarcoptic mites penetrate the upper layer of the skin and exca- 

 vate burrows or galleries in which the mating of the sexes occurs and 



