Sea otters in Washington state waters face potential threats from infectious diseases, federal researchers said in a study released Tuesday.

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Sea otters in Washington state waters face potential threats from infectious diseases, federal researchers said in a study released Tuesday.

The study found the otters are exposed to pathogens that have caused diseases in marine-mammal populations in other parts of the country.

Sea otters in Washington don’t appear to be suffering harm from those pathogens, but they still may be at risk because of their relatively small population and limited range.

“What surprised us was that disease threats were the biggest concern versus contaminants,” said Mary Sue Brancato, a study co-author and a resource-protection specialist at NOAA’s Olympic Coast National Marine Sanctuary in Port Angeles.

“Sea otters are a keystone species in the sanctuary, so potential disease threats are a significant concern for us,” she added.

Brancato said the population of sea otters is faring well and still expanding — they number more than 1,100 — but a disease outbreak or oil spill could be catastrophic for the small group.

The northern sea otters are federally protected under the Marine Mammal Protection Act and were listed as endangered in 1981 in Washington state.

Sea otters were common along Washington’s coast for thousands of years until they were wiped out in the early 1900s by fur traders. Otters from Amchitka Island, Alaska, were transplanted in 1969 and 1970 to reintroduce the species to the Washington coast.

Along with the sanctuary, the U.S. Fish and Wildlife Service and other agencies worked on the study to examine contaminants and pathogen exposure.

Researchers took blood and liver samples from sea otters off the Washington coast in 2001 and 2002.

There were traces of chemical contaminants, but the levels didn’t raise concerns, said Jay Davis, co-author and resource-contaminant specialist for the U.S. Fish and Wildlife Service.

Eighty percent of the otters tested positive for morbillivirus, which can cause serious disease in some animals and humans. It was the first time the virus was detected in sea otters, the study found.

About 60 percent of the otters tested positive for toxoplasmosis, a parasitic disease that has been responsible for the deaths of southern sea otters in California.

“Although we’re seeing evidence that they’re exposed, we’re not seeing mortality,” Brancato said. “It’s a very good sign.”