Stream pathogenic bacteria levels rebound post-population control of wild pigs

The range and density of one of North America's most destructive and invasive mammalian species, wild pigs (Sus scrofa), has expanded rapidly over the past several decades. Alongside this growth, their fecal contamination of surface waters has impaired water quality through significantly increased levels of pathogenic bacteria, raising concerns over the potential for zoonotic disease transmission. Significant remediation of these water quality impacts has been shown as a result of reductions in wild pig populations due to control efforts; however, the duration of these remediation effects as populations rebound remains unclear. Our study sought to determine the longevity of water quality remediation resulting from wild pig population control efforts. We found that median concentrations of Escherichia coli and fecal coliform (CFU/100 mL) increased by 746% and 159% in the year following the conclusion of removal efforts, resulting in median concentrations of 79% and 159% greater than those observed prior. We also found increased public health risk, with samples exceeding E. coli and fecal coliform guidelines 10% and 12% more often than pre-removal, respectively. While further research into wild pig population dynamics and fecal contamination is necessary, we conclude that ongoing population control efforts may be necessary to remediate water quality impacts and public health risks associated with invasive wild pigs.