'Unusual' beaver die-off in Utah caused by 'rabbit fever,' which can also infect humans

At least nine beavers and a vole have been found dead across Utah after an unusual outbreak of tularemia, a disease that can also infect and kill humans, cats and dogs. Local wildlife experts are concerned by the unprecedented spread of the disease and have warned people to take precautions.

Tularemia, also known as rabbit fever, is a bacterial disease that most commonly affects rabbits, hares, beavers, as well as other rodents, mammals and livestock. However, the bacteria, Francisella tularensis, has also been reported in fish, cats and dogs, according to the American Veterinary Medical Association. The disease has a high mortality rate, especially among wild animals.

Tularemia is also a zoonotic disease, meaning that it can jump between animals and humans. People can be infected with tularemia through several different pathways, including tick and deerfly bites, physical contact with infected animals, eating undercooked meat and by drinking contaminated water. Humans can die from the disease if the infection is not treated promptly with antibiotics, according to the Centers for Disease Control and Prevention (CDC). Symptoms of tularemia across species include fever, swollen glands, lethargy, and poor appetite. 

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Between March 23 and April 10, nine otherwise healthy-looking North American beavers (Castor canadensis) and a vole from an unnamed species were found dead, according to a statement by the Utah Division of Wildlife Resources (UDWR). 

The first five beavers were found at Swaner Preserve & EcoCenter near Park City and are all believed to have shared the same den. The other animals were subsequently found at three other locations: near Midway, near the Jordanelle Dam and in the Birdseye area of Utah County.

Four of the beaver carcasses from three separate locations — Swaner preserve, Midway and Birdseye — were sent for testing at Utah Veterinary Diagnostic Lab and the Utah Public Health Lab, and three of the specimens (one from each location) tested positive for tularemia, according to UDWR. There is therefore a high chance that the others also died from the disease.

Cases of tularemia are occasionally reported in animals and in humans across the U.S. but are normally isolated to a single animal or location. The last reported case of the disease killing wildlife in Utah was in 2017, when a single rabbit was found dead.

"It is unusual to see this many animals die from it at once," UDWR veterinarian Ginger Stout, said in the statement.

It is unclear why the disease has spread so quickly and widely but it may be linked to the start of the tick season, which normally begins in April.

The CDC recommends that people use insect repellent, frequently check themselves and their pets for tick or insect bites and try to avoid mowing over dead animals with lawnmowers, which can disperse the bacteria into the air. UDWR representatives also warned people to not pick up any dead animals they find and instead report them to the nearest UDWR office.