As the Arctic warms, more diseases will be introduced due to increased human activity and the migration of lower-latitude species to the north. Because polar bears range thousands of kilometres over ice, sea and land, they may be the “canary in the coalmine” for the spread of pathogens in the Arctic.
What We’re Learning
Exposure to pathogens is increasing
A study of Chukchi Sea polar bears suggests they are being exposed to more pathogens (bacteria, viruses, and parasites) than previously. Earlier studies in Western Hudson Bay and the Southern Beaufort Sea identified increased pathogen exposure in these bears, too.
Future research is needed to understand why exposure is increasing, and what it means for polar bears.
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How are polar bears exposed to pathogens? Does it relate to changes in behaviour, immune function, pathogen distribution and virulence, or some combination of those factors?
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How does exposure affect both individual and population health?
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Can we help manage the risk of exposure? For example, are the bears that congregate at whale carcasses at increased risk of infection? Would moving or redistributing the carcass help?
Climate, pollution and disease interact
Researchers found that the prevalence of some pathogens in polar bears correlated with hotter summers, more time on land and exposure to human settlements. Fasting bears break down their fat stores, releasing a spike of pollutants that can weaken their immune systems and make them more susceptible to disease.
“Bird flu” is an emerging concern
Avian influenza has been detected in polar bears in Alaska and Norway. This disease can cause an overwhelming immune response and mutate rapidly. Future research is needed to monitor avian influenza in polar bears.
Prey can be an important vector
Polar bears can contract Trichinella, a parasitic nematode, from prey — particularly seals. Understanding how disease spreads is important for mitigating the risk.