A preliminary investigation of Feral Hog (Sus scrofa) impacts on water quality

Authors: Brooks, John; Smith, Renotta; ALDRIDGE, CALEB - Mississippi State University; CHANEY, BRENT - Mississippi State University; OMER, AUSTIN - Mississippi State University; DENTINGER, JANE - Mississippi State University; STREET, GARRETT - Mississippi State University; BAKER, BETH - Mississippi State University

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2019
Publication Date: 2/11/2020
Citation: Brooks, J.P., Smith, R.K., Aldridge, C., Chaney, B., Omer, A., Dentinger, J., Street, G.M., Baker, B.H. 2020. A preliminary investigation of Feral Hog (Sus scrofa) impacts on water quality. Journal of Environmental Quality. 49; 27-37. https://doi.org/10.1002/jeq2.20036.
DOI: https://doi.org/10.1002/jeq2.20036

Interpretive Summary: Wild pigs can destroy cash crops on farms, but one aspect that is still being understood is the potential for surface water quality pollution related to wild pigs. A particular problem potentially associated with wild hogs is the contamination of water with nutrients, bacteria, and antibiotic resistant bacteria. Commercial pigs are known to carry many foodborne pathogens as such, it would be expected that feral pigs would also pose the same threat. The current study investigated the transfer of bacterial pathogens, antibiotic resistance, and nutrients to surface water from confined wild hogs. Overall, bacterial pathogens and nutrients were detected at higher levels in runoff below the hog containment, but not in the surface water. Surface water was generally not affected because of the grass buffer between the pigs and the surface water. In addition, bacterial pathogens and indicators were not elevated in downstream samples, possibly due to non-specific sources of bacteria and nutrients. Antibiotic resistance was also not affected by the confined pigs. Fecal droppings collected from the pigs did not show the presence of any antibiotic resistant DNA for the few tested resistance genes. Overall, this study demonstrated that wild pigs have the potential to contaminate surface water, but only if the pigs have access to the water.

Technical Abstract: The encroachment and subsequent destruction associated with feral hogs into prime farm land has been noted in the southern portion of the United States. Another environmental aspect associated with feral hogs is the transfer and related pollution with nutrients and pathogens into surface water. The current study aimed to identify potential impacts of impounded feral hogs on abiotic and biotic metrics of water quality, including nitrogen, phosphorus, fecal indicator bacteria, bacterial pathogens, antibiotic resistant bacteria, and antibiotic resistant genes. Overall, the study demonstrated that feral hogs potentially harbor pathogenic or fecal indicator bacteria capable of entering surface water streams such as Salmonella spp., Campylobacter spp., E. coli, and C. perfringens. While these bacteria were isolated from hog fecal matter, their presence in water samples was largely limited to runoff directly beneath the hog paddock, while implications to downstream water was limited due to a relatively large riparian buffer between the paddock and nearest surface water source. Ammonium was found to increase in runoff water below the paddock, which further bolstered the microbial results. Additionally, nutrients and microbial releases detected in runoff appeared to be time dependent, possibly associated with increasing hog numbers as the study progressed. Antibiotic resistance was generally not associated with the presence of the feral hogs and was often associated with non-point sources, particularly antibiotic resistance genes, which were found in upstream- as well as downstream- surface water suggesting that other sources of microbial and nutrient contamination were present. Overall, it appears that feral hogs pose a threat to water quality, but only if they have direct access to the water. Pathogen, fecal indicator bacteria, and some nutrient release was significantly associated with feral hogs, however riparian buffers limited water quality impairment.