The big question to be answered was how could a virus that causes a highly contagious measles-like disease called phocine distemper virus (PDV) in marine mammals spread so quickly from the Atlantic coasts to the Pacific coast?
“We didn’t understand how a virus from the Atlantic ended up in these sea otters. It’s not a species that ranges widely,” said Tracey Goldstein, a scientist at the University of California Davis who investigates how pathogens move through marine ecosystems, according to EcoWatch.
Goldstein and her colleagues spent 15 years looking at data that included climate and satellite images and everything from taking nasal swabs and blood samples from live-captured bearded seals, ribbon seals, spotted seals, and ringed seals, northern fur seals, Steller sea lions, and northern sea otters, as well as taking blood and tissue samples from dead animals recovered from beaches.
The conclusion reached by the study shows that the spike in the virus was commensurate with Arctic sea ice loss. The data, published in a new study in the journal Scientific Reports, finds that the loss of Arctic sea ice allowed otters and other mammals to move west and spread the virus.
“It was a perfect storm in 2002,” Goldstein 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.”
In studying sea ice loss from Russia to Alaska, the researchers found a link between sea ice losses in the Arctic and spikes in outbreaks of the disease. In particular, the scientists found that drastic reductions in sea ice on the Russian side of the North Atlantic coincided with increases in exposure rates in both ocean basins.
Goldstein says the melted ice was likely opening up new waterways for infected animals to come into contact with other species while breeding or foraging for food. “As animals move and come in contact with other species, they carry opportunities to introduce and transmit new infectious disease, with potentially devastating impacts.”
Phocine distemper virus
Phocine distemper virus, (PDV) is closely related to the canine distemper virus, which veterinarians vaccinate for. It spreads easily when an animal comes into direct contact with an infected animal. And while there is no evidence to suggest that PDV is transmittable to humans, the virus belongs to the same family as the measles. And like the measles, it’s highly virulent.
The virus manifests in seals much like the canine version does in dogs — goop discharged from the eyes and nose and a fever. With marine mammals, it also leads to erratic swimming. Pneumonia develops, and mortality can be high in previously unexposed animals.
According to the Merck Veterinary Manual, vaccination with a subunit vaccine is practiced in European rescue centers and appears to be protective, but this approach has not been applied in North America, in large part due to lack of availability of the appropriate vaccine.
The climate crisis is changing the spread of diseases
Enabling the spread of the distemper virus in marine animals is just one negative effect of the climate crisis. Warming of our oceans has also led to an increase in the number of toxic algae blooms, not only in our oceans but in freshwater lakes and ponds.
When we see these changes happening in animals, we can’t ignore them, because the impacts on people and the planet are not far behind,” said Elizabeth VanWormer, the study’s lead author, as NBC News reported. “This shows how interconnected these things are — the health of people, animals, and the planet.”
