Sea otters and seals in the Pacific off the coast of Alaska are infected with a virus that was previously observed only in animals in the Atlantic.
A new study suggests that melting ice in the Arctic could be to blame – and that climate change could help move the disease to new areas and new animals.
Tracey Goldstein, a biologist at the University of California, Davis, became curious when Sea Otters in the Pacific in 2004, two years after a large outbreak of European seals, tested positive for the Phocine Distemper Virus – a cousin of Canine Distemper Virus .
Until 2002, the oceans around the Arctic Circle remained largely frozen even in late summer. This year, the Arctic Ocean was passable between the North Atlantic and the Pacific at the end of the summer, she and her colleagues noted.
Although sea otters are not far from home, seals may have been able to transmit the virus from the Atlantic Ocean to the Pacific Ocean. Goldstein.
The melting of sea ice is a viable explanation for the spread of viruses – but not the only one, said Charles Innis, veterinarian and director of animal health at the New England Aquarium in Boston.
"A skeptic could argue that this virus could potentially be transmitted through an intermediate host, such as a bird that can fly far," said Drs. Innis, who was not involved in the new study. "Or maybe it will be transferred in the ballast water of ships or the like."
Even the illegal trade in pets or wildlife or spoiled meat shipped from coast to coast could spread a virus, he added.
DR. Goldstein and her team also investigated antibodies to the virus in the animals. In tests performed before the year 2000, there was no evidence of antibodies.
In 2002, however, the new study found a "considerable difference" in antibody levels in Steller sea lions, suggesting that the animals had active infections or had recovered from them.
The stagnant virus is quite deadly among the Atlantic seals. Hundreds of seals and seals were found dead on the coast of New England from Massachusetts to Maine in 2018 because they were infected with distemper and influenza.
But seals seem to be better able to survive distemper Goldstein said, and may serve as his reservoir – the ecological niche in which the infection persists. Outbreaks can occur when a sick seal comes into contact with a gray seal .
The outbreaks seem to be cyclical, Dr. Goldstein, because the animals build immunity to the infection. Every five to ten years, when new seals and otters are born and overall immunity diminishes, the population becomes vulnerable again and another outbreak occurs.
The new study identified a second wave of viral antibodies in 2009 in several seal species, including ice seals, northern fur seals and Steller sea lions. The current study ended in 2016, so it is not clear if the virus has spread since then, said Drs. Goldstein.
But she fears that another infection cycle is not far off. "These channels in the ice seem to be open every year, so these rare events could occur more often," she said.