Apr. 8, 1918 Sources of Hog-Cholera Infection 115 



conveyed by injection, susceptible pigs do not readily contract the disease 

 when fed with the infectious secretions and excreta or when exposed to 

 these materials scattered in pens. These experiments suggest that per- 

 haps the virus in the eye and nose secretions may be more readily con- 

 veyed by feeding and scattering than the virus in the urine and feces. 



Secretions and excreta collected on the fifth and seventh days and held 

 at room temperature (60° to 80^ F.) for 24 hours proved to be infectious 

 when injected. In the case of secretions and excreta which were col- 

 lected on the seventh day and held at room temperature (60° to 75° F.) 

 for 48 hours before injection, the urine and feces proved to be infectious, 

 but the eye and nose secretions were no longer so. It should be noted 

 that the eye and nose secretions were preser\^ed on swabs and had 

 dried before the last tests of virulence were made. 



Of the four cholera-infected pigs which furnished the secretions and 

 excreta for these experiments, two showed the first visible symptoms of 

 sickness on the fourth day after injection, one on the sixth day, and one 

 on the seventh day. As the experiments show that the virus is present 

 quite regularly in the eye and nose secretions and in the feces by the 

 third day, and may be present in the blood and urine as early as the first 

 day, it becomes at once apparent that a cholera-infected pig may be a 

 source of danger before the animal shows any visible symptoms of 

 disease. A subsequent experiment (No. V) proves this danger to be a 

 real one and that infected pigs may transmit the disease by contact dur- 

 ing the period of incubation and before the appearance of visible symp- 

 toms. In this connection the possibility suggests itself that mild, un- 

 recognized cases of hog cholera may occur and that such cases may be 

 a factor in the spread of hog cholera. 



CONTAGIOUSNESS OF HOG CHOLERA AT DIFFERENT STAGES OF THE 



DISEASE 



The object of the following experiments was to determine whether, by 

 mere contact, infected pigs are capable of transmitting hog cholera at 

 all stages of the disease or whether there are certain periods, early or 

 late, when the disease is not contagious. As will be seen, an endeavor 

 was made to reduce, as far as possible, the likelihood of infection through 

 contaminated pen litter. 



Experiment V. — The experiment was carried out in the following 

 manner: Three pigs. No. iioi, 1102, and 1103, were injected sub- 

 cutaneously with blood from a sick pig on November i and were at 

 once placed in a clean, disinfected pen, together with two uninoculated, 

 susceptible pigs. The injected pigs and the susceptible, exposed pigs 

 were allowed to remain together for 48 hours, at the end of which time 

 the injected pigs and the exposed pigs were transferred to separate, 

 clean, disinfected pens. Two more susceptible pigs were then placed 

 with the injected pigs in their clean pen for 48 hours. The injected and 



