The Expanded Role of Roof-Rats () in spp. Contamination of a Commercial Layer Farm in East Japan.

Rodents serve as amplifiers of infections in poultry flocks and can serve as a source of contamination in the environment even after thorough cleaning and disinfection. This study aims to determine the dynamics of occurrence in rodents and its relation to contamination in the layer farm environment, including air dusts and eggs. From 2008 to 2017, roof rats (), environmental swabs, air dusts, and eggs were collected from an intensive commercial layer farm in East Japan and were tested for spp. using standard procedures. In roof rat samples, the isolation rate was reached at 10% (95% confidence interval [CI] 8.1-21.9) in which Corvallis, Infantis, Potsdam, and Mbandaka were the frequent isolates from the cecal portion of the intestines. On the other hand, the prevalence rate of in environmental swabs was at 5.1% (95% CI 2.2-7.4) while air dusts were at 0.9% (95% CI 0.2-1.8). It was observed that the prevalence of predominant serotypes shifted over time; in roof rats, it was noted that Potsdam gradually replaced Infantis. In environmental swabs and eggs, Corvallis and Potsdam increased significantly while Infantis became less frequent. In air dusts, Corvallis was observed to decrease and Potsdam became more common. Based on our findings, the role of roof rats in the epidemiology of in layer farms was expanded from being a reservoir and an amplifier host into a shifting vessel of the most predominant serotypes.