Researchers: We Shared The Flu Virus With Olympic Peninsula Sea Otters

Apr 9, 2014

Humans are particularly generous with the flu, otter-wrangling scientists have found.

People shared the 2009 swine flu epidemic with ferrets, dogs, cats, raccoons and pigs, and new research shows even wild sea otters in Washington state got hit. 

"These otters, which we think were living in a relatively pristine environment off the Olympic Peninsula, were exposed to pathogens that are more commonly associated with people," said Virologist Hon Ip with the U.S. Geological Survey, who co-authored the study published in the May 2014 issue of “Emerging Infectious Diseases.”

Testing Sea Otters On The Peninsula

In 2011, some of Ip's colleagues went out to the Olympic Peninsula coast and donned some stealthy scuba equipment that allowed them to dive under unsuspecting sea otters without sending bubbles bumping into their floating backs. They netted some otters, took quick blood samples and released them.

Out of 30 otters tested, 21 had traces of certain antibodies that indicated that at one point, their immune systems had battled the 2009 H1N1 strain. (The testing took place two years after the flu passed, so they don't know if otters can get the same runny noses, nausea and fevers as infected people.) 

Transmission Goes Both Ways

The question of how people come into contact with otters — and enough so to get them sick — is an unsolved puzzle. It could have to do with another animal that catches the virus from people on land, then passes it to sea otters in the water. Elephant seals are the only other marine mammal known to have been infected with the pandemic H1N1 flu.

Regardless of how they got it, the fact that otters can be exposed to a human pandemic virus is an important finding. For one, it means the animals could be susceptible to a deadlier strain. 

Ip says the sea otters may have dodged a bullet in 2009. That virus, confusingly referred to as swine flu, proved widespread yet mild for humans. It also didn't make a dent in the sea otter population. But influenza strains are constantly evolving, and something as severe as the Spanish flu of 1918 — in which some patients woke up in the morning feeling fine, and died by nightfall — could crop up again. Since transmission can go both ways, that could be bad for sea otters and people alike. 

"The finding that sea otters are capable of being infected with influenza A virus means that a virus that will infect sea otters is likely to be able to infect us as well, too," Ip said. "So it may come back the other way around."  

Other Marine Mammals, Other Germs

Washington sea otters weren't the only marine mammals to be infected.

"Elephant seals also got exposed to the same strain of flu," said LeAnn White, a wildlife disease specialist and co-author of the paper. "They have a bit more contact with people because they haul out onto land more often, so there's potential for more contact with them." Whales have contracted earlier flu strains.

Another important finding was that otters also had increased exposure to other pathogens that tend to circulate among people, including a parasite called Toxoplasma gondii, which is commonly transmitted through contact with domestic cat poop. Tests in 2002 showed that about 58 percent of the otters had been exposed to the parasite. By 2011, the exposure rate jumped to 97 percent, tests showed. There's no telling how that happened.