138 PARASITIC SlCIN DISEASES. 



VITALITY OF THE PARASITES.— Under favourable circum- 

 stances, psoroptes may live as long as two mionths, when removed 

 from their host; sarcoptes live about half that time. 



INCUBATION. — The period required for the eggs of the mange 

 insect to become hatched, varies according to temperature, within, 

 of course, reasonable limits. Under ordinary circumstances the 

 period may be from two to ten days. The eggs may remain 

 fertile for a month. 



DURATION OF THE DISEASE.— Mange, in both the psoroptic 

 and sarcoptic forms, shows no tendency to spontaneous recovery. 

 The same might be said of symbiotic "mange; although in some 

 cases this disease may disappear with age, or ordinary grooming. 



EFFECT ON THE GENERAL HEALTH OF THE HORSE.— 



Sarcoptic mange greatly ailects the general health, especially if 

 allowed to run its course unchecked, in which case it may not 

 improbably cause death. During the Crimean campaign and the 

 Franco-German war, great numbers of horses died from the effects 

 of this kind of mange, aided by hardships and privation. Psoroptic 

 mange, owing to its slower spread, has not such quickly acting ill- 

 effects ; although it also has a very debilitating influence, which, 

 in neglected oases, may have a fatal result. 



TRANSMISSIBILITY OF MANGE TO OTHER ANIMALS.— As 

 the parasites which produce sarcoptic mange (or itch) in men, 

 horses, dogs, foxes, etc., respectively, are varieties of the same 

 insect (sarcoptes scabiei) ; the sarcoptic parasites of one species of 

 animal will, if transferred to the skin of another species, attack it ' 

 as a rule. In all cases, the occupation seems to be but temporary, 

 probably, not exceeding a month in duration ; although the disease 

 might be kept up by fresh importations of parasites. Among 

 troops, especially on active service, there have been several 

 instances of cavalry soldiers suffering a great deal from the 

 attacks of sarcoptes from mangy horses ; these must, however, 

 be regarded as exceptional. On the other hand, the itch insect 

 of man — ^whether on account of the horse's skin being thicker, or 

 by reason of lack of numbers — is but little formidable to the 

 horse. Hence, there is not much objection to men, afflicted with 

 itch, grooming sound-skinned horses ; of course, under circum- 

 stances of necessity. 



DIAGNOSIS. — The presence of the parasite is the only sign by 

 which to authoritatively determine the nature of the complaint. 



