Apr. s. 1918 Sources of Hog-Cholera Infection 131 



in the urine and feces, but such a conclusion is not justified by these 

 experiments, as the virus from the eye and nose was allowed to dry on 

 swabs. This point requires further study with the virus from the 

 different sources held under identical conditions. Finally, it should 

 be noted that the eye and nose secretions may be infectious before there 

 is any visible discharge from the eyes or nose. 



(2) Susceptible pigs were exposed by association with cholera-infected 

 pigs for 48-hour periods on the first, third, fifth, seventh, ninth, and 

 eleventh days after infection. With the exception of those exposed on 

 the first and second days — that is, during the first 48-hour interval — all 

 of the exposed pigs contracted hog cholera. Other pigs which were ex- 

 posed to cholera-infected pigs at 17 and 21 days contracted hog cholera. 

 Cholera-infected pigs therefore may transmit the disease by conta.ct at 

 practically all stages of the disease, even in the period of incubation, 

 before the appearance of visible symptoms and before the animal can be 

 recognized as sick. 



(3) Susceptible pigs were exposed by being placed in pens with pigs 

 which had suffered from typical attacks of hog cholera but had recov- 

 ered. Other susceptible pigs were inoculated with blood drawn from 

 the recovered pigs. Four recovered pigs were tested in this way to 

 determine whether they harbored the virus of cholera within their bodies 

 and might act as carriers of the disease. None of the pigs exposed to the 

 recovered pigs, either by association or by blood injection, developed hog 

 cholera. The exposed pigs were later proved to be susceptible by virus 

 injection. 



(4) Susceptible pigs were exposed for long periods of time to pigeons, 

 which passed daily from a heavily infected pen only 10 feet away and 

 which contained sick and dying pigs, to a pen containing suscepti- 

 ble pigs. The exposure in these experiments was severe, as the pig- 

 eons were afforded every opportunity to carry the infection over a very 

 short distance. Notwithstanding this, none of the exposed pigs devel- 

 oped cholera. All of the exposed pigs were later proved to be suscepti- 

 ble either by virus injection, by association directly with sick pigs, or 

 by exposure in an infected pen. These experiments extended through 

 the fall and well into the winter. While the assumption would hardly 

 be warranted that pigeons never convey hog cholera, it does not seem 

 likely that they are often concerned in the spread of this disease. 



(5) Rats were fed on the meat of cholera hogs for periods of 5 and 21 

 days. The rats were then killed, their entire bodies chopped up, mixed 

 with bran mash, and the mixture was fed to susceptible pigs. None of 

 the pigs thus fed contracted cholera. The pigs were proved to be sus- 

 ceptible by subsequent virus injection. 



