A recent publication has examined the epidemiology of Salmonella prevalence on egg-producing farms in Japan. This article provides statistics including odds ratios associated with a number of management and housing variables.
The authors considered a wide range of Salmonella in their research. Since the epidemiology of Group D Salmonella including S. Enteriditis differs from non-Group D serotypes, the conclusions in the trial should be carefully evaluated.
Univariate analysis of risk factors on one of the two farming groups considered, showed high odds ratios for induced molting, in-line egg processing and in-line processing.
A discordant observation was that farms which disinfected vehicles before entering the facility yielded a high odds ratio. Disinfection of vehicles before entering the farm had a high odds ratio for Salmonella infection which appears counter intuitive. The authors also found that suppression of rodents had no effect on the prevalence of Salmonella and that there was no protective effect from vaccination.
The results demonstrate contradiction with accepted knowledge and practice. Most certainly improving biosecurity, providing farm clothing to workers, diligent vaccination and intensive suppression of rodents all contribute to a reduction in the prevalence of SE on US farms. In order to interpret the results obtained from the study in Japan, it will be necessary to carefully evaluate the criteria used and to separate the results relating to Group D Salmonella from other serogroups.
Inevitably the opponents of intensive egg production will deliberately take out of context the apparent correlation between prevalence of Salmonella infection and operation of in-line units. This misinterpretation will be applied to discredit large facilities which provide the bulk of US eggs.