Studies on a Paratyphoid Infection in Guinea Pigs

Abstract

The appearance of a second type of Salmonella in a guinea pig population during the endemic stage of a spontaneous outbreak of paratyphoid disease was reportedin an earlier paper (1). The earliest eases of the first infection occurred in the summer of 1924. The associated organism became rapidly disseminated throughout the population; particularly through the breeding stock, and for a period of 8 weeks a moderately high specific death rate ensued. The epidemic subsequently declined to an endemic level which has persisted up to the present. The course of the infection was followed b y a bacteriological examination of all animals that died in the population under observation.During July and August, 1926, several strains of a second type of Salmonella were isolated from fatal cases. Subsequently there was a slow but general spread of the second organism. These natural occurrences, among the guinea pigs, afforded an opportunity for studying the course of a second infection in an animal population which had been exposed for a considerable period of time to a related but serologically distinct type of organism.A somewhat similar condition in a mouse population was described by Lynch (2). A spontaneous outbreak of paratyphoid infection, of 2 years duration, was followed by a second outbreak caused by a serologically different type of Salmonella. The two types of organism were designated Mouse Typhoid I and 11. Some 18 months prior to the second outbreak half of the population was vaccinated with a strain of Mouse Typhoid I. The specific death rate for the 2O7 on May 9, 2018 jem.rupress.org Downloaded from