With the rise in Arctic temperatures, polar bears are facing a higher risk of disease compared to those from thirty years ago. Karyn Rode and Caroline Van Hemert from the U.S. Geological Survey have made these observations in a recent study published on October 23, 2024, in the open-access journal PLOS ONE.
The environmental shifts brought about by global warming are providing new chances for viruses, bacteria, and parasites to infect wildlife in the Arctic. As a dominant predator with a vast habitat, polar bears are particularly susceptible to changes in how these pathogens are spread.
In their research, scientists analyzed blood samples from polar bears in the Chukchi Sea collected between 1987 and 1994, comparing them to samples taken thirty years later from 2008 to 2017. They searched for antibodies to six different pathogens. The findings showed that five of these pathogens were more frequently found in the later samples: the parasites responsible for toxoplasmosis and neosporosis, the bacteria causing rabbit fever and brucellosis, and the canine distemper virus. The rising rates of these pathogens indicate some of the fastest changes in exposure observed in polar bears.
Researchers also delved into the factors that heightened the bears’ risk of infection and discovered that exposure levels depended on their diet and was generally higher in female bears than in males. This increase may be linked to pregnant females choosing to den on land to care for their cubs.
In the Arctic, where temperatures are increasing nearly four times faster than the global average and polar bears are rapidly losing their sea ice habitat, the threat of infectious diseases is becoming a significant concern for wildlife officials and local communities. Indigenous hunters often rely on polar bears for food, and many of the pathogens identified in this study can be transmitted to humans. The researchers believe that, given the various stressors polar bears face due to climate change and their role as a vital food source, it is essential to further investigate these populations for signs of disease.
The authors emphasize that “In some cases, the number of polar bears showing positive serum antibodies—a marker of pathogen exposure—more than doubled, reaching some of the highest levels recorded in any population. These findings imply that the pathways for pathogen transmission have evolved in this Arctic ecosystem.”
