Polar bears face an alarming increase in disease risk amid shifts in the Arctic ecosystem

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• Polar bears in the Chukchi Sea show an increased risk of diseases that were previously uncommon for them over thirty years.
• The five most common pathogens in polar bears are parasites responsible for toxoplasmosis and neosporosis, bacteria that cause rabbit fever and brucellosis, and the canine distemper virus.
• The changes in polar bear exposure to pathogens are indicative of wider ecological shifts affecting other species in the Arctic ecosystem.

Blood samples from polar bears in Chukchi Sea collected over thirty years reveals an alarming trend: an increased risk of diseases that have not occurred before among the inhabitants of this Arctic. The researchers analyzed blood samples taken between 1987 and 1994, followed by a second set collected between 2008 and 2017. The results showed a significantly higher level of chemical markers indicating disease with viruses, bacteria or parasites in the most recent samples.

Although it is challenging to determine the exact impact on the physical health of bears from blood samples alone, wildlife biologist Dr. Karyn Rode from the US Geological Survey says this trend reflects wider changes within the Arctic ecosystem. The research focused on six specific pathogens – viruses, bacteria and parasites that are common in land animals, but sometimes also in marine animals, including those that polar bears hunt.

Pathogens in polar bears

Dr. Rode noted that the study period coincided with significant sea ice loss and increased land use for this unique population of polar bears. This led the researchers to investigate whether knowledge of these germs had changed, especially those that are more common on land. The five most common pathogens in polar bears include two parasites responsible for toxoplasmosis and neosporosis, two types of bacteria that cause rabbit fever and brucellosis, and the canine distemper virus.

Impact of the study

Despite how strong they are in terms of disease, Dr. Rode said that these findings highlight the ongoing changes in the Arctic. Polar bears are classified as an endangered species in the US, with the main threat to their survival being the loss of their habitat on sea ice – the essential hunting platform for marine prey.

Previous research using collar cameras on polar bears has shown that because they spend more time on land because there is less sea ice available, it is difficult for them to consume enough calories. Dr. Rode explained that polar bears, as top predators, get hold of these pathogens mainly through their prey. As a result, the observed changes in polar bear exposure to pathogens are indicative of broader ecological trends affecting other species within the Arctic ecosystem.

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