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Tularemia

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Tularemia is a disease of animals and humans caused by the bacterium Francisella tularensis. Rabbits, hares, and rodents are especially susceptible and often die in large numbers during outbreaks. Humans can become infected through several routes, including:
  • Tick and deer fly bites
  • Skin contact with infected animals
  • Ingestion of contaminated water
  • Laboratory exposure
  • Inhalation of contaminated dusts or aerosols

In addition, Tularemia is considered a potential bioterrorism agent. The Arkansas Department of Health has developed plans for the distribution of medical countermeasures in the event Tularemia is utilized as a bioterrorism agent against the general population. Those plans are maintained by the Preparedness and Emergency Response Branch (PERB), Strategic National Stockpile (SNS) program, and include guidance on medication utilization for clinicians.

Symptoms vary depending upon the route of infection. Although tularemia can be life-threatening, most infections can be treated successfully with antibiotics. Antibiotics used to treat tularemia include streptomycin, gentamicin, doxycycline, and ciprofloxacin. Treatment usually lasts 10 to 21 days depending on the stage of illness and the medication used. Although symptoms may last for several weeks, most patients completely recover.

    Epidemiology

    Tularemia has been a reportable disease in the United States since the 1920’s. The Arkansas Department of Health conducts surveillance and investigates cases of Tularemia reported in Arkansas.

    • Tularemia is the third most prevalent tickborne disease in Arkansas, and is found statewide.
    • Approximately 13 percent of all reported Tularemia cases in the U.S. occurred in Arkansas, from 2001-2010.
    • Tularemia in Arkansas can occur year round, with a higher instance in the spring through fall.

    Clinical Description

    Tularemia can be difficult to diagnose. It is a rare disease, and the symptoms can be mistaken for other more common illnesses. For this reason, it is important to ask about likely exposures, such as tick and deer fly bites, or contact with sick or dead animals. Blood tests and cultures can help confirm the diagnosis. The onset of tularemia is usually abrupt, with flu-like symptoms.

    The signs and symptoms of tularemia vary depending on how the bacteria enter the body. Illness ranges from mild to life-threatening. All forms are accompanied by fever, which can be as high as 104 °F. Main forms of this disease are:

    • Ulceroglandular - This is the most common form of tularemia and usually occurs following a tick or deer fly bite or after handing of an infected animal. A skin ulcer appears at the site where the organism entered the body. The ulcer is accompanied by swelling of regional lymph glands, usually in the armpit or groin.
    • Glandular - Similar to ulceroglandular tularemia but without an ulcer. Also generally acquired through the bite of an infected tick or deer fly or from handling sick or dead animals.
    • Oculoglandular - This form occurs when the bacteria enter through the eye. This can occur when a person is butchering an infected animal and touches his or her eyes. Symptoms include irritation and inflammation of eye and swelling of lymph glands in front of the ear.
    • Oropharyngeal - This form results from eating or drinking contaminated food or water. Patients with orophyangeal tularemia may have sore throat, mouth ulcers, tonsillitis, and swelling of lymph glands in the neck.
    • Pneumonic - This is the most serious form of tularemia. Symptoms include cough, chest pain, and difficulty breathing. This form results from breathing dusts or aerosols containing the organism. It can also occur when other forms of tularemia (e.g. ulceroglandular) are left untreated and the bacteria spread through the bloodstream to the lungs.

    Physicians who suspect tularemia should promptly collect appropriate specimens and alert the laboratory to the need for special diagnostic and safety procedures. Rapid diagnostic testing for tularemia is not widely available.

    Growth of F. tularensis in culture is the definitive means of confirming the diagnosis of tularemia. Appropriate specimens include:

    • swabs or scrapping of skin lesions
    • lymph node aspirates or biopsies
    • pharyngeal washings
    • sputum specimens
    • gastric aspirates, depending on the form of illness
    • blood cultures are often negative

    A presumptive diagnosis of tularemia may be made through testing of specimens using direct fluorescent antibody, immunohistochemical staining, or PCR.

    The diagnosis of tularemia can also be established serologically by demonstrating a 4-fold change in specific antibody titers between acute and convalescent sera. Convalescent sera are best drawn at least 4 weeks after illness onset; hence this method is not useful for clinical management.

    CaseDefinition

    The Arkansas Department of Health utilizes the Centers for Disease Control and Prevention (CDC) case definition for Tularemia. Current case definitions for all tickborne diseases can be found on the National Notifiable Diseases Surveillance System (NNDSS) website.

    Treatment

    Streptomycin is the drug of choice based on experience, efficacy and FDA approval. Gentamicin is considered an acceptable alternative, but some series have reported a lower primary success rate, and is not a U.S. Food and Drug Administration-approved use. Treatment with aminoglycosides should be continued for 10 days.

    Tetracyclines may be a suitable alternative to aminoglycosides for patients who are less severely ill. Tetracyclines are static agents and should be given for at least 14 days to avoid relapse.

    Ciprofloxacin and other fluoroquinolones are not FDA-approved for treatment of tularemia but have shown good efficacy in vitro, in animals, and in humans.

    Prevention

    Avoiding potential avenues of exposure is the best prevention for Tularemia. Antibiotic treatment following a tick bite is not recommended as a means to prevent Tularemia. There is no evidence this practice is effective, and this may simply delay onset of disease. For more in-depth information about prevention of tickborne disease, please visit our Prevention of Mosquito and Tickborne Disease section. Additional information on tickborne disease can be found at CDC’s Division of Vector-Borne Diseases (DVBD) webpage.