As the Arctic warms, polar bears are increasingly at risk of contracting diseases—viruses, bacteria, and parasites—that they were less likely to encounter three decades ago, according to recent research.

In a study linking polar bear health issues to Arctic ice loss, scientists examined blood samples from bears in the Chukchi Sea, located between Alaska and Russia.

Researchers compared samples collected between 1987-1994 with those gathered three decades later, from 2008-2017. The newer samples showed a notable increase in chemical markers indicating that polar bears had been exposed to five specific pathogens.

While it’s unclear how these infections impacted the bears’ health, wildlife biologist Dr. Karyn Rode from the US Geological Survey stated that the findings reveal significant changes within the Arctic ecosystem.

The study tested for six pathogens, typically associated with land animals but also found in marine animals that polar bears hunt.

The study covered three decades, Dr Rode said, “when there had been a substantial loss of sea ice and there’s been increased land use in [this population of polar bears]”.

“So we wanted to know if exposure had changed – particularly for some of these pathogens that we think are primarily land-oriented.”

The five increasingly common pathogens include two parasites causing toxoplasmosis and neosporosis, two bacteria responsible for rabbit fever and brucellosis, and the virus that leads to canine distemper.

“Bears in general are pretty robust to disease,” explained Dr Rode. “It’s not typically been known to affect bear population, but I think what it just highlights is that things [in the Arctic] are changing.”

Classified as a threatened species in the U.S., polar bears face their greatest threat from shrinking sea ice, which they rely on for hunting.

Studies using collar cameras show that as bears spend more time on land during ice-free periods, they struggle to find enough food to sustain them.

Dr. Rode noted that polar bears, as top predators, appear to be exposed to some of these pathogens primarily through their prey.

The shift in their exposure to these diseases highlights broader changes in the Arctic, potentially tied to their evolving interactions with other species as their habitat continues to melt.

Dr Rode explained that polar bears are top predators: “Our study suggested that they’re getting their exposure to some pathogens primarily through their prey species.

“So what we saw as changes in pathogen exposure for polar bears is indicative of changes that other species are also experiencing.”

The findings are published in the scientific jou, externalrnal PLOS One.