Community Environment Health & Wellness

Local case is first time tularemia, a rare infectious disease, spread from marine mammal to human

Epidemiologists with the Kitsap Public Health District have co-authored a new report documenting the first recorded case of a human contracting the infectious disease tularemia from a marine mammal.

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The finding, published last month in the Centers for Disease Control’s Morbidity and Mortality weekly report, details how a 32-year-old wildlife biologist from Kitsap County contracted the zoonotic disease after performing a necropsy on a dead harbor seal.

Tularemia, also known as “rabbit fever,”  is commonly found in rodents, hares and ticks. Humans can contract it through animal contact or contaminated water and food.

This is the first documented case in which scientists found the bacteria in a marine mammal.

Biologist fully recovered

The biologist, who works for a nonprofit, found the seal in the South Puget Sound. She performed the necropsy to determine if human interaction contributed to its death.

During the examination, she nicked her finger with a scalpel and cut through her gloves.

Nearly two weeks later, she went to a primary care provider for a reported fever plus swelling and pain on her left hand. Doctors prescribed medication and she fully recovered.

A harbor seal pup in Poulsbo in July. Photo by Meegan M. Reid/Kitsap Sun

Testing of a sample from her wound found Francisella tularensis, the bacteria that causes tularemia. The Kitsap Public Health District investigated. 

Wendy Inouye, a communicable disease epidemiologist with the KPHD and co-author of the report, said they were lucky that the case involved a scientist. The scientist handled the seal appropriately and its remains were available for testing by the Washington Animal Disease Diagnostic Laboratory and CDC.

“In this way, we were able to identify the disease-causing organism in the seal, and connect the seal to the human case’s infection,” Inouye wrote in an email. 

Bacteria natural in aquatic environments

Inouye described the finding as “surprising, but perhaps not shocking.” Scientists have found Francisella tularensis in more than 250 wild and domestic species. It is naturally present in aquatic environments, she said.

“It’s important to note though, that we don’t do animal surveillance testing for the tularemia bacteria, so we probably don’t know as much as we’d like to about how the bacteria circulates in the environment,” she said.

While tularemia is highly contagious, requiring only 10 to 50 bacteria to cause an infection — and is listed as a potential bioweapon by the CDC — it does not spread easily between people, said KPHD Health Officer Dr. Gib Morrow. Risk to the public is very low.

There are fewer than 10 cases per year in Washington and about 200 nationally, according to the CDC. Those working outside and near animals, including farmers, foresters and veterinarians, are most at risk of contracting the disease. Exposure to rabbits, hares or rodents likely causes most cases in Washington, Inouye said.

“This exposure often occurs through kicking up dust and aerosolized bacteria during yard work or landscaping activities,” she said.

Stay away from dead animals

Inouye said the public and their pets should remember to keep a safe distance from wildlife and report sick, injured or dead animals to wildlife agencies. This case, she said, is also a remainder of the connection between animal and human health.

“We do not routinely monitor animals for tularemia. However, because a person got sick, [KPHD] investigated and was able to connect the illness to a previously unknown animal source,” she said. “By sharing this finding, we helped increase knowledge of how this bacterium circulates in the environment, and how it could potentially be passed to people.”