SHIC Looks at Bacterial Spillover Between Species for Potential to Cause Emerging Disease

An ongoing collaboration between SHIC and the Center for the Ecology of Infectious Diseases at the University of Georgia examines spillover risk of bacteria from North American wild mammal species into the US swine herd. This collaboration will result in enhanced information needed to prevent, prepare, and respond to emerging diseases and their potential impact on swine health, welfare, and market.

The first phase of the project identified 102 bacteria species hosted by 127 North American wild mammal species that have a ≥ 97.1% chance of associating with domestic pigs. These bacteria species were assigned a propensity score based on their predicted ability of spilling over from their wild mammal hosts into domestic swine. A classification of either “novel” or “known” was also assigned based on whether or not these species had a known association with pigs documented in scientific literature.

A survey of subject matter experts was the second phase of the project. The goal of the survey was to rank the 102 bacteria species to assess their potential impact on the swine industry via potential effects on public health, antimicrobial resistance, and swine welfare, production, morbidity, and mortality. A limited number of industry professionals completed the survey and identified 16 bacteria species as being of high impact to the swine industry, four of which are not yet known to infect domestic swine: Anaplasma bovis (98.7% modeled chance of spilling over into swine), Clostridium botulinum (98.7%), Klebsiella pneumoniae (98.6%), and Yersinia pestis (99.7%). Additionally, seven bacteria were ranked as having a high-risk of antimicrobial resistance and five bacteria were ranked as having a high human outbreak potential. Results of the analysis uncovered two novel bacteria that are found in pigs, which helps validate the predictive model.

Industry professionals across disciplines hold valuable insights crucial to informing risks related to emerging diseases. Their collective knowledge based on years of expertise fills a gap in the absence of a comprehensive database on the pathogenicity of swine-associated bacteria. A lack of published academic literature also fuels the need to engage subject matter experts to develop a systematic process for identifying bacterial species of concern to the swine industry, and this research represents a summary of such an endeavor.

Due to the limited response to the qualitative survey, additional effort to increase its power by seeking more responses is underway. Other upcoming activities include continued work to investigate pathways for potential spillover events, such as shared habitats between wildlife and domestic swine, or pathogen overlap. Additionally, different bacterial strains, serovars, and variants of bacteria species of concern must be closely examined to increase predictive power.

Bacteria account for a high degree of morbidity and mortality in swine, causing huge losses to the swine industry and zoonotic risks. Domestic pigs often acquire these pathogens (either directly or indirectly) from wild animals, creating the need for assessments such as these to prioritize bacteria species for targeted prevention strategies.

SHIC, launched by the National Pork Board in 2015 solely with Pork Checkoff funding, continues to focus efforts on prevention, preparedness, and response to novel and emerging swine disease for the benefit of US swine health. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. SHIC is funded by America’s pork producers to fulfill its mission to protect and enhance the health of the US swine herd. For more information, visit or contact Dr. Paul Sundberg at [email protected].