An investigation of endemic fowl cholera, the common form of the disease in this locality, has been made at a poultry farm in Belle Meade, N. J. The focus or reservoir of P. avicida proved to be the healthy pullets which had become carriers the previous year and which were selected as the breeding stock for the ensuing season. From these carriers, the organisms spread and gave rise during the winter months to the various forms of infection, including the carrier state, localized upper respiratory disease, and typical cholera. Strains of P. avicida were in general very similar and of the "blue" colony type. They were all of the same low degree of virulence; no differences were demonstrable between a) "carrier" and "autopsy" strains, b) strains where the infection was spreading and severe, and strains where disease was rare, and c) "autumn" and "winter" strains. In general, a relatively high carrier rate was accompanied by a high mortality rate, although in one instance, a community with high carrier incidence plus a probable high degree of host resistance suffered but little fatal infection. An attempt was made to reduce the amount of cholera by the removal of carriers. The results of this measure indicate that such a procedure is both effective and practical.

Field studies of fowl cholera on two commercial poultry farms are described. One farm, previously free of cholera, was studied during an active epidemic, which occurred during the winter months. The strains of P. avicida recovered, both from "autopsy" and from "healthy carriers" proved generally similar, and to be of the "fluorescent" or "intermediate" colony type, which is of relatively high virulence. After the subsidence of the epidemic, these strains tended to disappear. The second flock consisted of a small group of birds which had survived an epidemic of cholera the previous year, and in which the infection was prevailing in endemic form. No deaths occurred during the period of observation, but the number of birds with localized lesions and the number of carriers increased to a high level during the winter months. The strains of P. avicida were apparently of the "blue" colony form, although some, as shown by their acid and serum agglutination reactions, resembled the "intermediates." These strains appeared to be spreading rather than dying out. The individual fowls differed in their response to the presence of infection; some showed localized lesions, others were carriers, while still others seemed entirely refractory.