Long‐term increases in pathogen seroprevalence in polar bears (Ursus maritimus) influenced by climate change

• Published in: Global change biology 2021-10, Vol.27 (19), p.4481-4497
• Main Authors: Pilfold, Nicholas W., Richardson, Evan S., Ellis, John, Jenkins, Emily, Scandrett, W. Brad, Hernández‐Ortiz, Adrián, Buhler, Kayla, McGeachy, David, Al‐Adhami, Batol, Konecsni, Kelly, Lobanov, Vladislav A., Owen, Megan A., Rideout, Bruce, Lunn, Nicholas J.
• Format: Article
• Language: English
• Subjects: Ablation; Antibodies; Aquatic mammals; Arctic; Body condition; Climate change; Environmental impact; Human settlements; Marine mammals; Parasites; Parvoviruses; Pathogens; Polar bears; Primary; Primary s; Sea ice; Serology; Serum; Summer; Survival; Toxoplasma gondii; Trichinella; Ursus maritimus; Wildlife; Wildlife conservation; wildlife disease; Zoonoses; zoonosis
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.15537

The influence of climate change on wildlife disease dynamics is a burgeoning conservation and human health issue, but few long‐term studies empirically link climate to pathogen prevalence. Polar bears (Ursus maritimus) are vulnerable to the negative impacts of sea ice loss as a result of accelerated Arctic warming. While studies have associated changes in polar bear body condition, reproductive output, survival, and abundance to reductions in sea ice, no long‐term studies have documented the impact of climate change on pathogen exposure. We examined 425 serum samples from 381 adult polar bears, collected in western Hudson Bay (WH), Canada, for antibodies to selected pathogens across three time periods: 1986–1989 (n = 157), 1995–1998 (n = 159) and 2015–2017 (n = 109). We ran serological assays for antibodies to seven pathogens: Toxoplasma gondii, Neospora caninum, Trichinella spp., Francisella tularensis, Bordetella bronchiseptica, canine morbillivirus (CDV) and canine parvovirus (CPV). Seroprevalence of zoonotic parasites (T. gondii, Trichinella spp.) and bacterial pathogens (F. tularensis, B. bronchiseptica) increased significantly between 1986–1989 and 1995–1998, ranging from +6.2% to +20.8%, with T. gondii continuing to increase into 2015–2017 (+25.8% overall). Seroprevalence of viral pathogens (CDV, CPV) and N. caninum did not change with time. Toxoplasma gondii seroprevalence was higher following wetter summers, while seroprevalences of Trichinella spp. and B. bronchiseptica were positively correlated with hotter summers. Seroprevalence of antibodies to F. tularensis increased following years polar bears spent more days on land, and polar bears previously captured in human settlements were more likely to be seropositive for Trichinella spp. As the Arctic has warmed due to climate change, zoonotic pathogen exposure in WH polar bears has increased, driven by numerous altered ecosystem pathways. Western Hudson Bay (WH) polar bear serum samples were analysed for antibodies to seven pathogens across three time periods: 1986–1989, 1995–1998 and 2014–2017. Antibodies to zoonotic pathogens increased between the 1980s and all other time periods, and were driven by environmental variables undergoing climate change. The increase in antibodies was greatest between 1986–1989 and 1995–1998, a period during which WH polar bears experienced declines in abundance, body condition and reproductive output.