Deadly virus in marine animals could be linked to Arctic sea ice loss driven by climate change
Scientists have linked the decline in Arctic sea ice to the emergence of a deadly virus that could threaten marine mammals in the North Pacific, according to a 15-year analysis.
A pathogen called phocine distemper virus (PDV)—which was responsible for killing thousands of European harbor seals in the North Atlantic in 2002—was identified in northern sea otters in Alaska in 2004, raising questions about when and how the virus reached them.
The research team found that reshaping of the sea ice could have opened pathways for the contact between the Arctic and sub-Arctic seals that were previously impossible. This, in turn, allowed for the virus's introduction into the Northern Pacific Ocean. Loss of ice opened pathways for disease transmission among sea lions, ice seals, sea otters, and others.
The researchers caution that as sea ice continues its melting trend owing to climate change, the opportunities for this virus and other pathogens to cross between North Atlantic and North Pacific marine mammals may become more common.
"Our study allowed us to detect widespread exposure to and infection with phocine distemper virus across the North Pacific Ocean beginning in 2003 and viral transmission across multiple marine mammal species. Peaks of phocine distemper virus exposure and infection followed reductions in Arctic sea ice extent, potentially linking climate change to the introduction of PDV into the North Pacific Ocean," Tracey Goldstein, associate director of the One Health Institute at the University of California (UC) Davis School of Veterinary Medicine, told MEA WorldWide (MEAWW).
Shifts in the environment, such as loss of sea ice, may drive exposure to new pathogens by changing animal behavior and opening up water routes that allow for contact between previously distinct populations, explains the team.
According to the researchers, the findings highlight the need to understand phocine distemper virus transmission and the potential for outbreaks in sensitive species within this rapidly changing environment.
"Climate change-driven alterations in Arctic environments can influence habitat availability, species distributions, and contact and the breeding, feeding, and health of marine mammals. People in the Arctic also rely on marine mammals for subsistence. Climate change-driven reductions in sea ice extent in the Arctic Ocean are projected to increase. The health impacts of this new normal in the Arctic are unknown. But the association of open water routes through Arctic sea ice suggest that opportunities for phocine distemper virus and other pathogens to cross between North Atlantic and North Pacific species may become more common," Goldstein told MEAWW.
The research team investigated the timing of phocine distemper virus introduction into the North Pacific, the risk factors associated with its emergence and patterns of transmission. They used data on phocine distemper virus exposure and infection in ice seals, steller sea lions, northern fur seals, and sea otters, as well as animal movement data, collected between 2001 and 2016.
The researchers identified widespread infection and exposure to the virus in sea mammals in the North Pacific Ocean in 2003 and 2004, with over 30% of animals testing positive for the virus. The prevalence of phocine distemper virus then declined in the following years until peaking again in 2009, shows analysis. These peaks coincided with reductions in Arctic sea ice extent, says the study published in Scientific Reports.
The team says that the chances of viral infection were 9.2 times higher in animals sampled in 2004 and 2009 relative to other years. This was associated with the presence of open water routes in 2002, 2005, and 2008, detected using satellite imagery. Satellite telemetry data helped the researchers link animal movement and risk factor data to demonstrate that exposed animals have the potential to carry phocine distemper virus long distances.
"The loss of sea ice is leading marine wildlife to seek and forage in new habitats and removing that physical barrier, allowing for new pathways for them to move. As animals move and come in contact with other species, they carry opportunities to introduce and transmit new infectious disease, with potentially devastating impacts," says Goldstein.