Enteric bacterial pathogen detection in southern sea otters (Enhydra lutris nereis) is associated with coastal urbanization and freshwater runoff

Abstract

Although protected for nearly a century, California’s sea otters have been slow to recover, in part due to exposure to fecally-associated protozoal pathogens like Toxoplasma gondii and Sarcocystis neurona. However, potential impacts from exposure to fecal bacteria have not been systematically explored. Using selective media, we examined feces from live and dead sea otters from California for specific enteric bacterial pathogens (Campylobacter, Salmonella, Clostridium perfringens, C. difficile and Escherichia coli O157:H7), and pathogens endemic to the marine environment (Vibrio cholerae, V. parahaemolyticus and Plesiomonas shigelloides). We evaluated statistical associations between detection of these pathogens in otter feces and demographic or environmental risk factors for otter exposure, and found that dead otters were more likely to test positive for C. perfringens, Campylobacter and V. parahaemolyticus than were live otters. Otters from more urbanized coastlines and areas with high freshwater runoff (near outflows of rivers or streams) were more likely to test positive for one or more of these bacterial pathogens. Other risk factors for bacterial detection in otters included male gender and fecal samples collected during the rainy season when surface runoff is maximal. Similar risk factors were reported in prior studies of pathogen exposure for California otters and their invertebrate prey, suggesting that land-sea transfer and/or facilitation of pathogen survival in degraded coastal marine habitat may be impacting sea otter recovery. Because otters and humans share many of the same foods, our findings may also have implications for human health.

Dynamics of Vibrio with Virulence Genes Detected in Pacific Harbor Seals (Phoca vitulina richardii) Off California: Implications for Marine Mammal Health

“…It is possible that stranded individuals may not have enough energy reserves to leave the shore and may accidentally ingest V. cholerae contaminated water or sediment near freshwater run-off sites. Sea otters (Enhydra lutris) using similar habitat consumed invertebrates near freshwater run-off sites and had similar prevalence of V. cholerae as stranded seals in this study [58]. Additionally, different species of Vibrio may associate with different prey or substrate types among regions [20,45,66].…”

“…This species is considered a pathogen of invertebrates, although it is rarely associated with disease in mammals [58]. In some cases, V.…”

“…Harbor seals often have strong site fidelity to areas near dense human populations (e.g., San Francisco Bay), and forage opportunistically on available benthic and pelagic prey [9,23,62,69,84,91]. Terrestrial inputs from urbanized coastal communities may alter the quality of habitat or food resources exploited by harbor seals [32,53,58,70,72,82]. These inputs also may contribute to increases in marine pathogens [39,42], thereby leading to an increasing incidence of disease in marine animals including harbor seals.…”

“…Vibrio species have been detected in marine mammals suffering from enteritis and septicemia [58,83]. Species of Vibrio also were detected in harbor seals, although the virulence of these strains was unknown [32].…”

“…Species of Vibrio also were detected in harbor seals, although the virulence of these strains was unknown [32]. Measuring the abundance, distribution, and virulence potential of Vibrio from seals and corresponding environmental conditions may aid in identifying processes that promote pathogen proliferation and thus may impact seal health [58,83]. and Humboldt Bay (HB) using beach seine, drift net, or hand-held salmon nets [32].…”