108 PARASITES OF THE DOMESTIC ANIMALS 



varieties of the sarcopt accidentally conveyed from their natural to a 

 foreign species of host meet with an unfavorable habitat and, if cutaneous 

 manifestations follow, it may be assumed that they must in any case be 

 slight and of relatively short duration. 



Psoroptic Scabies of the Horse. — Psoroptic scabies generally appears 

 about the regions of the longest hair, as at the base of the forelock, mane, 

 and tail. It at once gives rise to pruritus, which is accompanied by 

 rubbing and matting of the hairs as in mange, with which form it is 

 somewhat similar as to its course and alterations. It spreads much 

 more slowly, however, and rarely involves the whole surface of the 

 body. 



The psoropt does not burrow beneath the skin's surface as does the 

 sarcopt, therefore it can be more easily found. The methods recom- 

 mended for securing the Sarcoptes will apply to the Psoroptes as well, 

 though to obtain the latter it is not necessary to go quite as deeply for 

 the material. In this connection it should be borne in mind that two 

 or all three forms of scabies may coexist on the horse. It is advisable, 

 therefore, in certain cases to look for the mite in material obtained from 

 various affected regions of the body, as from the base of the mane, fore- 

 lock, or tail, from the cheeks and breast, and from the lower parts of the 

 legs. 



Lesions. — While the local alterations in psoroptic scabies are severe, 

 the pruritus intense, and the scabs generally thicker than in the sarcop- 

 tic form, it is a less serious affection in that the mites do not burrow, 

 and the lesions remain much longer localized. More easily and promptly 

 cured, it is not so frequently epizootic, and it is not as likely to spread to 

 other horses upon the same premises. 



Transmission. — As to its transmissibility from the equine species to 

 other animals, what has been said relative to this of the Sarcoptes 

 applies also to the Psoroptes. 



Chorioptic Scabies of the Horse. — This form of scabies begins on 

 the extremities, most often the hind feet about the fetlocks and pasterns. 

 From here it spreads to the hocks, or to the knees if from the fore feet, 

 sometimes extending further, but rarely as far as the bod}^ Like the 

 psoroptes, these mites seek the parts covered by long hair, therefore 

 horses with long fetlocks are predisposed to attack. 



Symptoms. — The first symptom of the invasion is itching, which 

 the hoi'se manifests by stamping, kicking the side of the stall, efforts to 

 bite the legs, or rubbing them one against the other. This irritation 

 is especially noticeable upon the animal's return from work and at night 

 in a warm stable. Its true caiise is frequently overlooked in considering 

 it a vicious habit. 



Chorioptic scabies is slow in development, and is most troublesome in 

 winter. This is probably due to the fact that the feet of horses at this 



