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

Abstract

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.

Widespread Exposure to Mosquitoborne California Serogroup Viruses in Caribou, Arctic Fox, Red Fox, and Polar Bears, Canada

“…We identified high CSG virus seroprevalence in caribou populations, some of which are declining across northern Canada, emphasizing the need to determine whether caribou are reservoir hosts and whether JCV affects health and fecundity of these animals. Our finding of increased CSG virus seroprevalence in polar bears over time demonstrates the utility of comparing prevalence of climate sensitive diseases against baseline values for species known to be affected by rapid climate change (18,50). We identified summer air temperature as a key factor influencing polar bear exposure to CSG viruses, suggesting that infections will likely become more prevalent as the climate continues to change.…”

Socio-economic predictors of Inuit hunting choices and their implications for climate change adaptation

“…For example, uncertainty in weather, such as unpredictability of the direction or strength of winds, are major concerns for hunters (Fox 2002), and changes in sea ice cover affect hunters' access and the behaviour, distribution, and migration timing of marine mammals (Huntington et al 2013;. Climate change also impacts access to country food through changes in the availability of key species due to changes in population health, size, or migration routes (e.g., Bradley et al 2005;Burek et al 2008;Pilfold et al 2021), or due to wildlife management policies, such as hunting bans or quotas introduced for beluga whale or caribou (Kishigami 2005; Kenny et al 2018b).…”

Drivers of polar bear behavior and the possible effects of prey availability on foraging strategy

“…Greater habitat fragmentation has increased polar bear path tortuosity [ 9 ], more open water has increased the frequency of long-distance swimming events [ 105 , 115 ], and increased ice drift speed has increased the cost of station-keeping [ 5 , 34 , 90 ]. Further, polar bears have exhibited shifts in distribution [ 85 ], reduced access to prey [ 45 , 147 , 160 ], a longer fasting period [ 127 ], increased exposure to zoonotic pathogens [ 116 ], higher levels of cortisol [ 13 ], reduced body condition [ 127 , 144 ], reduced access to denning habitat [ 96 , 127 ], reduced reproduction [ 146 ], and consequently reduced abundance in several populations [ 14 , 87 , 101 , 123 , 124 ]. The ecological effects of climate change on polar bears are population specific.…”