106 



PARASITES OF THE DOMESTIC ANIMALS 



or late stages, the diagnosis of sarcoptic mange may be made positive 

 by the recovery of the Sarcoptes. This should be looked for as soon as 

 the presence of mange is suspected, as it is important to know with what 

 form of the disease we have to deal. The nymphte and pubescent males 

 and females live upon the body surface and among the crusts over all 

 affected parts. Innnediately after they become impregnated the oviger- 

 ous females burrow galleries beneath the epidermis in which they deposit 

 their eggs and live for a time with the young larva? (Fig. 65) . In man the 

 course of the galleries is marked by fine red lines from 8 to 15 mm. or 

 more in length, but in the horse these cannot be seen owing to the 

 thickness and pigmentation of the epidermis. The sarcopt is usually 

 lodged at the extreme end of the channel in the course of which her eggs 



Fig. 66. — Colts affected with advanced sarcoptic mange (from author's i)hotograph) 



are distributed. It has been estimated that approximately fifteen in- 

 dividuals will be produced in each of these subepidermic burrows, and 

 that about fifteen days are required, under average conditions, for their 

 full development and the appea^rance of the next succeeding generation. 

 The larvae issuing from the eggs live in the gallery for some time before 

 finally making their exit along its course, while the parent female soon 

 dies after ovulation is completed. Copulation takes place upon the 

 skin beneath the crusts, the males dying after the performance of this 

 function. As the males are also relativeh^ less in number, it is the fe- 

 males which are more often met with. 



To secure the parasite for examination the crusts should be removed 

 and skin scrapings taken in such a manner as to include a portion of 

 serous exudate with the epidermic scales. The material should be taken 

 from a part showing evidences of recent attack, the mites being more 

 hkely to be found there than in the older lesions. This material, to- 



