At this stage the all-important point to determine was whether the disease which existed in this country, “verrucous endocarditis,” was communicable from pig to pig, and with this object numerous experiments have been conducted to discover whether the bacilli found within the hearts of diseased pigs were pathogenic to healthy swine.
A large number of healthy pigs have been fed or inoculated with the blood, the diseased portions taken from the valves of the heart, and with artificial cultures of the bacilli obtained from the heart, but in no instance has the attempt to produce this disease been successful.
PNEUMONIA OF THE PIG.
The occasional association of pneumonia with or without pleurisy in cases of swine fever has led many veterinarians in England to regard lung complications as one of the lesions produced by that disease.
In the Board of Agriculture’s report for the year 1894 a description was given of the various diseases in the lungs of swine which had come under notice, and it was therein stated that the Board had been unable to discover any special lesion of the lung which would warrant them in stating that it was indicative of swine fever or due to contagion.
It is an indisputable fact that pigs are extremely liable to pneumonia and pleurisy. But as the clinical appearances present in the lungs examined in no wise differed from those which take place in the lungs of other animals which have been exposed to cold or septicæmia and other causes, the Board’s officers have never accepted these lesions as being specific.
It is well known that both in Germany and the United States outbreaks of pneumonia of a contagious nature attributed to the presence of a bacillus pathogenic to the pigs of those countries are reported to occur. Indeed, contagious pneumonia of swine under the names of schweineseuche in Germany and swine plague in America are regarded as one and the same disease.
In view of the fact that in a large number of cases pneumonia, more or less extensive, sometimes associated with pleurisy, was found among the specimens forwarded to London, it was considered desirable that the departmental committee should institute a series of experiments to decide whether we had in this country a form of pneumonia in the pig which was communicable from one pig to another.
Accordingly a series of bacteriological experiments were conducted by Professor McFadyean with a view to isolate, if possible, a microorganism which would be capable of inducing pneumonia in healthy pigs. A number of diseased lungs, some of which were taken from pigs affected with swine fever, were examined microscopically by him, and, as was to be expected, several organisms were isolated, but they proved to be morphologically and culturally different from the bacillus of swine fever. Inoculations were carried out with these organisms not only subcutaneously but directly into the lung through the walls of the chest, and feeding experiments were also conducted. The results of these experiments were entirely negative; a certain amount of local injury was caused to the lungs at the seat where they had been punctured, but in no case was either pneumonia or swine fever induced.
The experiments have therefore demonstrated that the pneumonia found in the lungs of pigs affected with swine fever is not due to the swine fever bacillus.