As the Arctic warms, polar bears face a growing risk of contracting viruses, bacteria and parasites that they were less likely to encounter just 30 years ago, research has revealed.
In a study that has provided clues about how polar bear disease could be linked to ice loss, scientists examined blood samples from bears in the Chukchi Sea – between Alaska and Russia.
They analysed samples that had been gathered between 1987 and 1994, then collected and studied samples three decades later – between 2008 and 2017.
The researchers found that significantly more of the recent blood samples contained chemical signals that bears had been infected with one of five viruses, bacteria or parasites.
It is difficult to know, from blood samples, how the bears’ physical health was affected, but wildlife biologist Dr Karyn Rode from the US Geological Survey said it showed that something was changing throughout the whole Arctic ecosystem.
The researchers tested for six different pathogens in total – viruses, bacteria or parasites that are primarily associated with land-based animals but have been recorded before in marine animals, including species 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 pathogens, as disease-causing agents are collectively called, that have become more common in polar bears, are two parasites that cause toxoplasmosis and neosporosis, two types of bacteria that cause rabbit fever and brucellosis, and the virus that causes canine distemper.
“Bears in general are pretty robust to disease,” explained Dr Rode. “It’s not typically been known to
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