522 



siiseeptible to contract the disease, but 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., again acts as a predisposing cause as in the other infectious dis- 

 eases. The period of final dentition is a moment of the animal's life 

 which renders it peculiarly susceptible. 



Dupaul states that the infection is transmissible through the atmos- 

 phere for several hundred yards. The more common means of conta- 

 gion 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 suffering 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 return to the farms 

 where they are surrounded by young animals to whom they convey 

 the contagion. The saddle of the harness and croup straps are fre- 

 quent agents of infection. The presence of a wound greatly favors 

 the inoculation of the disease, which is also sometimes carried by sur- 

 gical 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 dis- 

 ease, which developed on the edges of the Avound. There is no elective 

 point for the first development of the disease, but it commences most 

 frequently around the natural openings, as these are points whicli are 

 most exposed to inoculation. 



Symi^toms.— 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 sum- 

 mer and longer in winter. At the end of this time, small nodes 

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

 The nodes, which feel like small shot under the skin, soften into small 

 pustules and break into little, shallow, superficial ulcers, exuding a 

 creamy, thick matter, which rapidly dries and forms scabs. The 

 horse is dull and dejected, loses its appetite, and has a rough di-y coat 

 with the hairs on end. There is moderate thrist. The respirations 

 are somewhat quickened and the pulse Ijecomes rapid and full. ^The 

 body temperature is elevated, frequently reaching 104° or 105° F., 

 within thirty-six or forty-eight hours from the appearance of the first 

 symptoms. 



The visible mucous membranes, especially the conjunetivse, are of 

 a bright rosy red. In the lymphatic, cold-blooded, and more common 

 horses these symptoms of fever are less marked; even with a com- 

 paratively high temperature the animal may retain its appetite and 

 even work comparatively well, but these cases, if worked and over- 

 heated, are apt to develop serious complications. 



