Zoos: Rodents Play a Major Role in the Transmission of Zoonoses

Globally, rodents carry numerous zoonotic agents. To limit human exposure and the transmission of these zoonoses, it is therefore particularly important to determine their prevalence and circulation among these animals, which harbor up to 85 different pathogens. The intermingling of human and animal populations in zoos—and particularly of rodents—places these facilities at the forefront of the early detection and identification of risk areas, as well as new hosts and high-risk pathogens, in line with a “One Health” approach.   Rodents account for more than 40% of mammal species. They are also one of the taxonomic groups most likely to harbor and transmit zoonotic diseases. They are capable of transmitting a wide range of microbial pathogens directly or indirectly. Their transmission potential makes them a threat to public health, and it is important to better characterize the actual risk posed by these reservoirs to limit exposure at the human-animal interface. Although the role of rodents in the transmission of zoonotic diseases has been characterized in urban settings, the environment of zoos is particularly well-suited to such a study. Zoos are, in fact, environments where both human and animal populations come together and intermingle. In zoos, the potential impact of rodents on infection dynamics is multifaceted, as they are present not only as captive animals but also in the wild or as food for other species. When combined with the close coexistence of different species in confined spaces and interaction with visitors and staff, zoos provide an environment conducive to zoonotic transmission, particularly by rodents. Despite this risk, no study to date has assessed the extent of exposure to rodent-transmitted zoonoses in zoos. To address this gap, American researchers conducted a literature review to quantify and characterize the presence of—and potential exposure to—zoonotic agents transmitted by rodents in zoological institutions worldwide. A total of 207 publications demonstrating the presence of or exposure to pathogens carried by rodents, from 43 countries and more than 140 zoos, were included in the analysis. Among these, 143 types of infectious agents were identified, including 14 viruses, 31 bacteria, 83 parasites, and 15 fungi. Furthermore, 75% of these pathogens had zoonotic potential. The wide range of rodent species and pathogens identified in zoos highlights the major role that these facilities could play in the early detection and identification of at-risk geographic regions, new hosts, or zoonotic agents harbored in rodent populations that have a significant impact on endangered species or humans. Indeed, the COVID-19 pandemic has taught us that it is particularly crucial to better inform and prioritize surveillance strategies, control programs, biosecurity, and preventive medicine in order to reduce exposure, infection, and transmission of zoonotic agents. The mixing and interactions between animals and humans in zoos illustrate the importance of adopting a “One Health” approach to better target surveillance and thereby reduce the risks of disease transmission by rodents.