Healthcare Providers
- An ongoing tularemia outbreak in wildlife in the Larimer County poses an exposure risk to people who contact sick or dead rabbits, or who are bitten by vector deer flies or ticks.
- Human tularemia is a serious and potentially life-threatening febrile illness. Patients may present with varied signs and symptoms depending on their route of exposure to the bacterium.
- All suspected cases of human tularemia must be reported immediately to public health so that disease control measures can be implemented as soon as possible. A laboratory diagnosis is not required to report a suspect case.
Tularemia is a disease caused by the gram negative bacterium Francisella tularensis. All warm-blooded animals are susceptible to tularemia, including livestock and pets such as dogs, cats and birds. These bacteria normally circulate in nature in lagomorphs (rabbits and hares), small rodents such as voles and muskrats, and in beavers, and commonly cause mortality. While infected, these animals can shed bacteria in their feces and urine, and once they die their carcasses will also still be infectious. The bacteria can persist in soil and water for several weeks to months. Ticks and biting flies can transmit the bacteria among animals and to people and their pets. People and their pets can also become infected from direct contact with infected animals, by drinking contaminated water, by inhalation of the bacteria from environmental sources, by contaminated soil entering skin abrasions or cuts, and by ingestion. The infective dose of this bacterium is very small.
Infected pets such as cats may transmit the disease to people. Person-to-person transmission of tularemia has not been documented. Some actions that people can take to help prevent tularemia infections include 1) protecting themselves from tick and deer fly bites, 2) not handling sick or dead animals without personal protection such as gloves and 3) avoid walking barefoot on lawns where dead rabbits have been found.
RECOMMENDATIONS / GUIDANCE: Tularemia is difficult to diagnose because it is a rare disease and the same symptoms may be observed with other diseases. View the clinical forms of human tularemia.
There are several clinical manifestations of tularemia, all of which are potentially life-threatening. These include ulceroglandular, glandular, oculoglandular, oropharyngeal, pneumonic, typhoidal, and septicemic. A patient's presentation and clinical signs will vary depending on the route of exposure (bite, ingestion, inhalation, cut, etc.). The incubation period can range from 2 to 14 days. Infected people will develop a fever up to 104 °F. Other symptoms may include ulcerations of the skin or mucosa, lymphadenopathy, vomiting, diarrhea, coughing and chest pain. Tularemia is a rare disease and many symptoms are non-specific. Patient presentation and clinical signs may vary greatly depending on the route of exposure. Because of this, several of the 2014 tularemia cases in Colorado went a week or more without adequate antibiotic treatment, and most were hospitalized for treatment. Providers should maintain a high index of suspicion for this condition, particularly in areas where animal die-offs have been reported, or in patients engaging in frequent outdoor activities.
Diagnostic testing
Clinical specimens such as blood, swabs of affected areas (such as ulcers), and biopsies from lesions or lymph nodes can be tested by PCR, fluorescent direct fluorescent antibody (DFA) assays, immunohistochemical staining, or by growth on culture media. Doctors may diagnose tularemia in a patient by requesting culture of the bacteria from patient samples. Swabs or scrapings from skin ulcers, lymph node aspirates, sputum or pharyngeal washes, or gastric aspirates are all acceptable samples for bacterial culture. Blood cultures are not a preferred sample and do not often grow the bacteria. Because the infectious dose for this bacterium is extremely low, laboratories should be advised that tularemia is suspected. Biosafety Level III precautions should be used when handling samples for culture. Tularemia patients may also need a chest X-ray to see if they show signs of pneumonia. A serological diagnosis of tularemia can be made by documenting a 4-fold change in antibody titer between acute and convalescent serum samples. A single titer of greater than 1:128 may be considered presumptively positive, but such levels are generally not reached until nearly 2 weeks after onset of symptoms, so serological testing is not generally useful for clinical management of a patient. An early negative serology does not rule out tularemia.
Treatment
Streptomycin is the drug of choice for treatment. Other antibiotics such as gentamicin and the tetracyclines may be used to treat tularemia. Fluoroquinolones are not FDA-approved for the treatment of human tularemia but have been used successfully. The choice of antibiotic can depend on the form of tularemia the patient presents with and the severity of illness. Antibiotics may be prescribed for a period of 10 to 21 days depending on the patient's condition. It can take several weeks to recover from tularemia. Immunity to re-infection is generally considered to be life-long.
Early detection and treatment is imperative to improve outcomes for human tularemia cases. We advise emergency room physicians and other medical providers to inquire about local die-offs in the patient's neighborhood, possible exposures to wildlife and sick pets, and to consider tularemia in patients presenting with these symptoms.
Suspected cases of human tularemia should be reported to the Larimer County Health Department 970-498-6700 or to the state health department at 303-692-2700 so that disease control measures can be implemented.
For more specific information about diagnosis and treatment go to CDC - Clinicians - Tularemia.
