Computer-based analysis of epidemiological data arising from salmonellosis in pigs.

Abstract

Computer-based analyses of epidemiological data recorded during the course of an outbreak of Salmonellosis and eventual eradication of Salmonella in a closed pig herd made it possible to assess statistically the influence of many of the variables involved. A number of conclusions were reached. The main route of cross-infection was contact with other infected animals. This occurred when infected and non-infected pigs were mixed in pens and at the times of service. Uninfected animals placed in disinfected pens and not moved from those pens usually remained free of infection, indicating that little cross-infection occurred between pens. Of all pigs found to be excreting Salmonella on one or more occasions, a large proportion (over 50%) were subsequently found, by faecal examinations, not to be excreting Salmonella. As the number of pigs per pen increased, a correspondingly high incidence of infection was found. The most susceptible age group was 3 to 7 months. Intercurrent disease and associated chemotherapy, vaccination and the use of a common weighing pen had little or no influence upon the incidence of infection.