DISEASES OF HORSES 75 



HORSEPOX, OR EQUINE VARIOLA. 



This disease is a specific infectious fever of the horse attended 

 by an eruption of pustules, or pocks, over any part of the skin or 

 on the mucous membranes lining the various cavities in the body, 

 but chiefly, and often exclusively, upon the pasterns and fetlocks. 

 The eruption may commence upon the lips, or about the nostrils 

 or eyes. 



Variola in the horse, while it is identical in principle, general 

 course, complications, and lesions with variola in other animals, is 

 a disease of the horse itself, and is not transmissible in the form of 

 variola to any other animal ; nor is the variola of any other animal 

 transmissible to the horse. Cattle and men, if inoculated from a 

 case of horsepox, develop vaccinia, but vaccinia from the latter ani- 

 mals is not so readily reinoculated into the horse with success. If 

 it does develop, it produces the original disease. 



Causes. The direct cause of horsepox is infection. A large 

 number of predisposing causes favor the development of the dis- 

 ease, as in the case of strangles, and this trouble, like almost all con- 

 tagious diseases, renders the animal which has had one attack im- 

 mune. The chief predisposing cause is young age. Old horses 

 which have not been affected are less apt to become infected when 

 exposed than younger ones. The exposure incident to shipment, 

 through public stables, cars, etc., acts as a predisposing cause, as in 

 the otner infectious diseases. The period of final dentition is a time 

 of the animal's life which renders it peculiarly susceptible. 



Dupaul states that the infection is transmissible through the 

 atmosphere for several hundred yards. The more common means 

 of contagion is by direct contact or by means of fomites. Feed 

 boxes and bridles previously used by horses affected with variola 

 are probably the most frequent carriers of the virus, and we find the 

 lesions in the majority of cases developed in the neighborhood of 

 the lips and nostrils. Coition is a frequent cause. A stallion suffer- 

 ing from this disease may be the cause of a considerable epizootic, 

 as he transmits it to a number of brood mares and they in turn re- 

 turn to the farms where they are surrounded by young animals to 

 whom they convey the contagion. The saddle and croup straps 

 are frequent agents of infection. The presence of a wound greatly 

 favors me inoculation of the disease, which is also sometimes carried 

 by surgical instruments or sponges. Trasbot recites a case in which 

 a set of hobbles, which had been used on an animal suffering from 

 variola, were used on a horse for a quittor operation and transmitted 

 the disease, which developed on the edges of the wound. 



Symptoms. There is a period of incubation, after an animal 

 has been exposed, of from five to eight days, during which there is 

 no appreciable alteration in the health. This period is shorter in 

 summer than in winter. At the end of this time small nodes de- 

 velop at the point of inoculation and the animal becomes feverish. 

 The horse is dull and dejected, loses its appetite, and has a rough 

 dry coat with the hairs on end. There is moderate thirst. The 

 respirations are somewhat quickened and the pulse becomes rapid 



