Exposure of Alaska brown bears (Ursus Arctos) to bacterial, viral, and parasitic agents varies spatiotemporally and may be influenced by age

Authors: RAMEY, ANDREW - Us Geological Survey (USGS); CLEVELAND, CHRISTOPHER - University Of Georgia; HILDERBRANT, GRANT - Us Geological Survey (USGS); JOLY, KYLE - Us National Park Service; GUSTINE, DAVID - Us Geological Survey (USGS); MANGIPANE, BUCK - Us National Park Service; LEACOCK, WILLIAM - Us Fish And Wildlife Service; CRUPI, ANTHONY - Alaska Department Of Fish And Game; YABSLEY, MICHAEL - University Of Georgia; Dubey, Jitender; Hill, Dolores

Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2018
Publication Date: 12/17/2018
Citation: Ramey, A.M., Cleveland, C.A., Hilderbrant, G.V., Joly, K., Gustine, D.D., Mangipane, B., Leacock, W.B., Crupi, A.P., Yabsley, M.J., Dubey, J.P., Hill, D.E. 2018. Exposure of Alaska brown bears (Ursus Arctos) to bacterial, viral, and parasitic agents varies spatiotemporally and may be influenced by age . Journal of Wildlife Diseases. 576-588. https://doi.org/10.7589/2018-07-173.
DOI: https://doi.org/10.7589/2018-07-173

Interpretive Summary: We collected blood and serum from 155 brown bears inhabiting five locations in Alaska and tested samples for evidence of prior exposure to a suite of bacterial, viral, and parasitic agents to: (1) gain inference on exposure of bears from three previously unsampled areas to pathogens, (2) explore potential differences in antibody seroprevalence relative to location, sex, and age, (3) investigate seroconversion and seroreversion for resampled bears, (4) assess if prior observations regarding spatial and age-related trends in seroprevalence are supported through analysis of contemporary samples, and (5) evaluate possible changes in exposure over time for bears inhabiting previously sampled areas. Antibody seroprevalence among Alaska brown bears was estimated to be 5 -44% for Brucella spp., Francisella tularensis, Leptospira spp., canine adenovirus type-1 (CAV-1), canine distemper virus (CDV), canine parvovirus, influenza A virus (IAV), and Toxoplasma gondii. No samples were positive for Bartonella spp. or antibodies to Trichinella spp. Point estimates of prior exposure to pathogens among brown bears at previously unsampled locations generally fell within the range of estimates for previously or contemporaneously sampled bears in Alaska. Statistical support was found for variation in antibody seroprevalence among bears by location, sex, and/or age cohort for CAV-1, CDV, IAV, and T. gondii. We found evidence for seroconversion and seroreversion in at least one bear for six different infectious agents. There was limited concordance in comparisons between our results and previous serosurveys regarding spatial and age-related trends in antibody seroprevalence among Alaska brown bears suggestive of temporal variation. However, we found evidence that seroprevalence of CAV-1 antibodies is consistently high in southwest Alaska and cumulative probability of exposure may increase with age. Results of this study increase our collective understanding of disease risk to both Alaska brown bear populations and humans and that utilize this public resource.

Technical Abstract: Brown bears (Ursus arctos) are among the largest extant terrestrial carnivores and exhibit a circumpolar distribution. In North America, this species occurs at highest population densities in Alaska, USA, specifically at coastal areas with seasonally abundant runs of Pacific salmon (Oncorhynchus spp.; Miller et al. 1997). While Pacific salmon represent a calorie-rich food source that supports high densities of animals, increased body mass, and improved reproductive success of pregnant females (Hilderbrand et al. 1999), brown bears often utilize diverse prey (Mowat and Heard 2006; Mangipane et al. 2017) and exhibit seasonal or sustained omnivory (Hilderbrand et al. 1996). Given high population densities and dietary plasticity, Alaska brown bears may be exposed to a diversity of bacterial, viral, and parasitic agents via intraspecies contact and through consumption of varied prey. Thus, assessments of exposure of Alaska brown bears to a variety of pathogens may be informative for understanding potential population-level impacts of disease and for assessing risk of human exposure to zoonotic pathogens through harvest (Maynard and Pauls 1962).