Incidence and Pathogenicity of Yersinia pseudotuberculosis and Yersinia enterocolitica in a Large Rhesus Macaque (Macaca mulatta) Colony (2000–2024)

Comprehensive epidemiological reports on the incidence and pathogenicity of Yersinia spp., specifically Yersinia pseudotuberculosis and Yersinia enterocolitica, in rhesus macaques (Macaca mulatta) are not prevalent. Here we report findings from a retrospective analysis of microbial culture results, necropsy reports, and histology records collected over 24 years (2000–2024) in a large captive rhesus macaque colony at the Oregon National Primate Research Center (ONPRC). Findings are compared between animals infected with either Y. pseudotuberculosis or Y. enterocolitica to evaluate the prevalence of infection within the population and determine whether Y. pseudotuberculosis is more likely to be associated with systemic disease and higher mortality than Y. enterocolitica. Among 101 affected animals, Y. pseudotuberculosis was the predominant species (75.2%), followed by Y. enterocolitica (22.7%) and Y. kristensenii (2.0%). Overall mortality among animals with confirmed yersiniosis was 25.3%, with comparable mortality rates for Y. pseudotuberculosis (23.7%) and Y. enterocolitica (30.4%) infections. Y. pseudotuberculosis was most frequently associated with systemic illness, spontaneous death, or significant clinical decline. Overall, these findings emphasize the importance of continued surveillance and targeted management strategies to mitigate the impact of Yersinia infections in captive nonhuman primate colonies.