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Tularemia

(This page is part of a series. For information on other illnesses that can affect NPS employees, volunteers, commercial use providers, and visitors, please see the NPS A–Z Health Topics index.)
Cottontail rabbit sitting among the plants
Cottontail rabbit

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THE BASICS
Tularemia is a highly infectious illness caused by the bacterium Francisella tularensis that affects both animals and humans. It is most commonly transmitted through the bite of infected ticks and biting flies but can also be transmitted by inhaling aerosolized bacteria from landscaping activities, contact with broken skin, and ingestion of infected meat or contaminated water. It can be spread through laboratory exposure but is not known to spread person-to-person. Naturally occurring infections have been reported in all states except Hawaii. Although numbers vary from year to year, approximately 250 U.S. cases are reported to the CDC annually. Tularemia can occur throughout the year but more commonly occurs in warmer months. Because it is so infectious, it is considered to be a potential bioterrorist threat.

Humans: Symptoms include fever and flu-like symptoms such as chills, lethargy, headaches, muscle aches, abdominal pain, vomiting and diarrhea. Additional symptoms depend on how a person was infected and can include skin ulcers, swollen lymph nodes, eye inflammation, sore throat, mouth ulcers, and pneumonia. Symptoms usually develop 3–5 days after exposure, although the range can be as wide as 1–21 days. Illness can be severe and result in death but is treatable with antibiotics, especially if treated early. Post-exposure prophylaxis is also available after an exposure to prevent illness. Although vaccines have been developed in the past, there is no vaccine currently available in the U.S.

Animals: Tularemia primarily affects mammals, but there have been rare cases of disease in birds. Many animals with tularemia are found dead, as clinical signs are rapid and often severe. Lagomorphs (e.g., cottontail rabbits, jackrabbits, hares) and rodents (e.g., voles, beavers, and muskrats) are especially susceptible to tularemia and can die in large numbers during outbreaks. Rabbits and rodents exhibiting clinical signs may be depressed, anorexic, easy to capture, and have a wobbly gait. Some may have roughened coat and a tendency to huddle. Ticks that transmit F. tularensis to humans include the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (D. andersoni), and lone star tick (Amblyomma Americanum). Deer flies (Chrysops spp) have been shown to transmit tularemia in the western United States.

Environment: F. tularensis can survive in the environment for long periods of time and is highly resistant to freezing temperatures. Infected animal carcasses/hides, dust, hay, water, and soil may harbor viable bacteria for weeks to months. F. tularensis is thought to be continuously maintained in a cycle between tick species (serving as a disease reservoir) and wildlife species. Disease may be more likely during years of heavy rainfall and increased rodent populations.


PREVENTION
  • Use an EPA registered insect repellent on skin when outside, as well as permethrin on clothing.
  • Check yourself for ticks at the end of the day; shower soon after spending time in tick habitat; and remove attached ticks promptly using tweezers.
  • Don’t drink untreated water.
  • Keep dogs leashed, cats indoors, and all pets supervised to reduce risk of contact with wildlife. Pets should be kept up to date with flea/tick preventatives.
  • If an exposure is suspected, contact your doctor immediately, as post-exposure prophylaxis can prevent illness.
  • Hunters: Use gloves when handling animals and cook game meat thoroughly before eating.
  • Employees:
    • Wear protective clothing and footwear. This may include wearing long sleeves and long pants, tucking pants into socks, and wearing a hat or cap.
    • Avoid mowing over dead animals. Consider wearing mask while mowing or landscaping.
    • Practice Safe Work Practices when handling animals.

RESPONSE
  • If you think you may have been exposed, contact a healthcare provider and let them know of your concern, as early antibiotic therapy is recommended for exposures as well as illness.
  • If you become ill following a potential exposure, contact your healthcare provider and let them know of your concern. Also, please report any confirmed illnesses to the NPS Office of Public Health publichealthprogram@nps.gov as directed in the “Disease Reporting” guidance below.
  • Report concerns about sick or dead wildlife to the park resource manager and the Wildlife Health Branch at e-mail us.

(Last updated 7/20/2023)
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RESOURCES:
NPS-SPECIFIC PUBLICATIONS:
  • Harrist A, Cherry C, Kwit N, et al. Francisella tularensis Exposure Among National Park Service Employees During an Epizootic: Devils Tower National Monument, Wyoming, 2015. Vector Borne Zoonotic Dis. 2019;19(5):316-322. doi:10.1089/vbz.2018.2360
  • Cherry CC, Kwit NA, Ohms RE, et al. Tularemia (Francisella tularensis) in a Black-Tailed Prairie Dog (Cynomys ludovicianus) Colony. J Wildl Dis. 2019;55(4):944-946.
  • Adjemian J, Weber IB, McQuiston J, et al. Zoonotic infections among employees from Great Smoky Mountains and Rocky Mountain National Parks, 2008-2009. Vector Borne Zoonotic Dis. 2012;12(11):922-931. doi:10.1089/vbz.2011.0917
  • Eisen L, Ibarra-Juarez LA, Eisen RJ, Piesman J. Indicators for elevated risk of human exposure to host-seeking adults of the Rocky Mountain wood tick (Dermacentor andersoni) in Colorado. J Vector Ecol. 2008;33(1):117-128. doi:10.3376/1081-1710(2008)33[117:iferoh]2.0.co;2
  • Gese EM, Schultz RD, Johnson MR, Williams ES, Crabtree RL, Ruff RL. Serological survey for diseases in free-ranging coyotes (Canis latrans) in Yellowstone National Park, Wyoming. J Wildl Dis. 1997;33(1):47-56. doi:10.7589/0090-3558-33.1.47

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Last updated: July 20, 2023