When a deadly virus, which killed tens of thousands of European harbor seals in the northern Atlantic Ocean in the year 2002, began threatening seals, sea lions, and otters in the northern Pacific Ocean, scientists were puzzled at first. The extremely contagious ‘phocine morbillivirus,’ formerly known as ‘phocine distemper virus (PDV),’ which does not affect humans, attacks the nervous and respiratory systems of a few marine mammals. However, there was no indication that it had infected animals that might have carried it to other parts across the globe. “How did a virus that had previously been seen in the Atlantic Ocean end up in the Pacific Ocean?” wondered Tracey Goldstein, Associate Director, One Health Institute, University of California, Davis, School of Veterinary Medicine.
Goldstein and some of her research team members examined 15 years of data that incorporated measurements of Arctic sea ice as well as data from animals that had been tagged by the National Oceanic and Atmospheric Administration as well as other organization to study their migration patterns. Melting Arctic sea ice brought on by the Earth’s humid climate created a way for the virus to move into a new area and infect a new sea life. “It was a perfect storm in 2002,” she said. “It was the lowest ice year on record at the time, and at the same time, in August and September, there was a really large outbreak.” The work of Goldstein and her colleagues, published recently, also used blood and nasal swab samples from sea lions, seals, and otters from southeast Alaska to Russia to evaluate which populations had been infected with the virus, and which precise strain they had been exposed to.
The researchers noticed an association between spikes in outbreaks of the disease and sea ice losses in the Arctic. In particular, the scientists found that severe reductions in sea ice on the Russian side of the North Atlantic coincided with rises in exposure rates in both ocean basins. The melted ice, Goldstein stated, was likely opening up new waterways for infected animals to come into contact with other species