372 Acarology 



apparently attacks only the concha. Marine 1924 gives the following 

 description of the symptoms: "The earliest manifestations of infection 

 are indicated by hyperemia and the formation of reddish brown crusts 

 near the bottom of the concha. The hyperemia and crust formation 

 extend and after months may involve nearly all the inner surface of 

 the ear. The most serious complication of the disease is pyogenic in- 

 fection of the middle ear which may extend to the internal ear and 

 meninges. The parasite spreads more rapidly during the warm months. 

 The disease is widespread, and few, if any, laboratories escape its 

 occasional introduction." 



Psoroptic mange is to be encountered on horses and cows. That of 

 the horse is common in France and is also present in England. It is 

 probably widespread. 



Psoroptes eqiii var. bovis causes the common cattle scab. As is the 

 case with the other members of the genus the entire life cycle of the 

 mite is passed upon the host. Imes 1918 reports: "The first lesions on 

 cattle appear on the withers, on top of the neck or just in front of the 

 withers, or around the root of the tail. From these points it spreads 

 over the back and sides and unless checked it may involve practically 

 the entire body. When a scab mite finds lodgment on the body it 

 pricks the skin to obtain food and in so doing probably introduces a 

 poisonous secretion into the wound. A slight inflammation is caused, 

 but this early stage of the disease is rarely, if ever, detected by casual 

 observation. As the mites multiply, large numbers of small wounds 

 are made in the skin and are followed by intense itching, formation 

 of papules, inflammation, and exudation of serum. The serum which 

 oozes to the surface becomes mixed with particles of dirt and more 

 or less infected with microorganisms. This mass soon hardens into 

 yellowish or gray-colored scabs which frequently are stained with 

 blood. In the early stages of the disease the scab may be about the 

 size of a pea, but as the mites seek the healthy skin around the edges 

 of the wound the scab or lesion gradually increases in size." 



The genus Chorioptes consists of several species which may actu- 

 ally be nothing but physiological varieties as in Psoroptes. They are 

 to be found on horses, cattle, sheep, goats and a few other animals. 

 Chorioptes bovis (Gerlach) is usually restricted to the feet or to the 

 base of the tail and anal fossa in cattle. In some cases it spreads on 

 to the neck and back, or to the belly and perineum. This mange is 

 usually of a mild type, remaining localized and spreading slowly. Other 

 species are C. equi (Hering) on horse, C. caprae (Delafond) on goat. 



