Emerging infectious diseases have significantly increased in recent years; approximately 60% of these emerging diseases are of zoonotic origin, and of those, around 70% were identified to start with wild animals. To better understand the impacts of zoonotic diseases on wildlife, there is a need to identify the distribution and impact of zoonotic pathogens in wildlife, particular those species with threatened populations. To investigate this question, we constructed a zoonotic disease database identifying wildlife hosts for each bacterial zoonotic disease and recorded clinical signs of disease for each host-pathogen relationship if found. Species of least concern were found to have a significantly higher prevalence and richness of zoonotic bacterial diseases (n= 0.0608, x²= 5.898, p=0.01516). The taxonomic level Order was found to be the best predictor for pathogen richness, and the Artiodactyla and Carnivora contain a significantly higher pathogen richness than other vertebrate Orders. Species with the greatest pathogen richness include the wild boar (Sus scrofa, n=66), Northern raccoon (Procyon lotor, n=16) and the red fox (Vulpes vulpes, n=41). Our results indicate bacterial zoonoses are not likely to be a driving factor of species population declines, and future zoonotic disease surveillance efforts should target species in the Artiodactyla and Carnivora families. The wild boar (Sus scrofa) in particular may be a good candidate for zoonotic disease monitoring due to its high pathogen richness, wide range, and large population. Understanding the impacts and distribution of bacterial zoonoses in wildlife populations can help in planning for future wildlife management efforts, particularly in species of conservation concern and wildlife disease monitoring.

Literature Review

From July 2020 to December 2022, We performed a literature review to identify wildlife hosts and clinical signs of bacterial zoonotic disease infection using Web of Science as the primary search engine. Supplemental searches were also conducted using PubMed, Google Scholar, and books or articles from the University of Missouri libraries. We identified zoonotic bacteria species using an updated version of a previously published pathogen database. We included pathogens that have been reported to cause disease in humans once and those found to cause disease only in immunocompromised patients. We excluded pathogen infections as a result of deliberate laboratory exposure, and pathogens found only in domestic species. In addition, we included recently recognized pathogen species from the Center for Diseases Control (CDC), Merck Veterinary Manual, and published literature.

Two separate database searches were conducted, the first to identify the wildlife host ranges of each zoonotic bacteria and the second to identify clinical signs as a result of zoonotic bacterial infection in each individual wildlife species. Titles and abstracts were examined, and articles were retained for further review when there was evidence of zoonotic bacterial pathogen infection in wildlife but not as a result of artificial inoculation.

Wildlife Hosts of Zoonotic Bacteria

To identify the wildlife hosts for zoonotic bacterial diseases, We used the following terms to identify host species: “Pathogen genus name” and “Wildlife” or “Pathogen species name” and “Animal.” If pathogen genus and species names had changed recently, both names were searched to ensure all available information was found. For the purpose of this research, “Wildlife” is defined as wild animals but also captive animals that would typically be wild such as zoo animals, privately owned animals, or those on nature preserves. Wildlife common names and scientific names were standardized using the red list of International Union for the Conservation of Nature (IUCN). Signs of disease were recorded from the first search if they were described in the articles.

Clinical Signs

To identify clinical signs for each wildlife species associated pathogen, We used the following terms to identify signs of disease: “Pathogen species name” and “Species scientific name” or “Species common name.” In cases where scientific name has changed recently, or there are multiple common names for the species, each variation was searched to ensure all available information was identified. “Signs” were defined as physical or mental abnormalities wildlife experience as a result of bacterial infection (i.e., vomiting, pyrexia, lesions, depression, etc.). Signs were included when they were identified as a result of the zoonotic pathogen infection. In many cases signs of disease and living animals has not been observed, so necropsy and histology findings were also included as signs of disease.

Exclusion criteria

Animals used for agriculture were not included as host species; however, clinical signs described in agricultural animals may have been used when the zoonotic pathogen had already been identified in wildlife populations. Signs of disease were included when they were definitively linked to the bacterial pathogen infection. Bacterial species that are normally found as a part of an animal’s microbiota such as bacteria of the Enterobacteriaceae family were not included unless they were linked to an infection or were found in an abnormal location. Articles were limited to the English language only. Duplicate articles were removed when necessary. For both searches, reference lists of the identified studies were also checked for additional studies.