PORCINE CONTAGIOUS PLEUROPNEUMONIA. I. EXPERIMENTAL TRANSMISSION, ETIOLOGY, AND PATHOLOGY

An acute frequently rapidly fatal respiratory illness occurring as an epidemic disease in Argentine swine has been shown to have a bacterium of the genus Hemophilus as its causative agent. This organism, for which the name Hemophilus pleuropneumoniae is suggested, causes a singular, fulminating pleuropneumonia in experimental swine. The very marked effectiveness of H. pleuropneumoniae as a respiratory pathogen contrasts strikingly with the relatively mild pathogenicity of the well known swine Hemophilus, H. influenzae suis, which, in concert with a virus, causes a less highly fatal respiratory ailment, swine influenza. Porcine contagious pleuropneumonia (PCP) is contagious under experimental conditions. In the pathogenesis of the disease, histopathological studies of early cases suggest that the lymphatics of the lung and pleura may be primarily involved and that the pneumonia and pleuritis then proceed from these initial sites of reaction.

PORCINE CONTAGIOUS PLEUROPNEUMONIA. II. STUDIES OF THE PATHOGENICITY OF THE ETIOLOGICAL AGENT, HEMOPHILUS PLEUROPNEUMONIAE

Hemophilus pleuropneumoniae is highly pathogenic for swine when given intranasally. As few as 100 organisms induce characteristic porcine contagious pleuropneumonia (PCP) and, when as many as one-half million are given, the infection usually proceeds to a fatal termination. While the organism is highly pathogenic when introduced by way of the respiratory tract, it is innocuous when given subcutaneously even in large numbers. Swine that have been inoculated subcutaneously are rendered solidly immune to infection with H. pleuropneumoniae intranasally. The marked pathogenicity of H. pleuropneumoniae for swine has been contrasted with the lack of pathogenicity of another swine Hemophilus, H. influenzae suis. It has been pointed out that, in its high degree of pathogenicity, in its pneumotropism, and in its immunogenicity by a non-respiratory route of inoculation, H. pleuropneumoniae appears to resemble certain viruses more than it does a bacterium.

PORCINE CONTAGIOUS PLEUROPNEUMONIA. 3. INTERRELATIONSHIP OF HEMOPHILUS PLEUROPNEUMONIAE TO OTHER SPECIES OF HEMOPHILUS: NUTRITIONAL, METABOLIC, TRANSFORMATION, AND ELECTRON MICROSCOPY STUDIES

Hemophilus pleuropneumoniae, the causative agent of porcine contagious pleuropneumonia (PCP) is an encapsulated organism that has the metabolic features of the parainfluenza group of Hemophilus in that it requires DPN but not hemin for growth. Its formation of nitrate reductase cytochrome a₁ and non-physiologically reducible cytochrome c₁ in the stationary phase, together with its requirement of electron transport through oxidases for growth are typical of non-hemin-requiring Hemophilus species. It has the closest genetic homology, judged from the capacity of its DNA to induce transformation to streptomycin resistance, with H. parasuis but can be differentiated from this organism on the basis of its growth in defined medium and its marked and characteristic pathogenicity for swine.