Tularemia - Infectious Diseases - MSD Manual Professional Edition (2024)

Tularemia is a febrile disease caused by the gram-negative bacterium Francisella tularensis; it may resemble typhoid fever

There are 7 clinical syndromes associated with tularemia (see table Types of Tularemia); clinical manifestations vary by the type of exposure to the organism.

The causative organism, F. tularensis, is a small, pleomorphic, nonmotile, nonsporulating aerobic, gram-negative bacillus that enters the body by

  • Ingestion of contaminated food or water

  • Bite of an infected arthropod vector (ticks, deer flies, fleas)

  • Inhalation

  • Direct contact with infected tissues or material

Tularemia does not spread from person to person.

Table

The organism can penetrate apparently unbroken skin but may actually enter through microlesions.

Two types of F. tularensis cause most cases of tularemia:

  • Type A: This type is a more virulent serotype for humans; it usually occurs in rabbits, hares, and rodents in the US and Canada.

  • Type B: This type usually causes a mild ulceroglandular infection and occurs in rodents and in aquatic environments throughout the Northern Hemisphere, including North America, Europe, and Asia.

Hunters, butchers, farmers, and fur handlers are most commonly infected. In winter months, most cases result from contact (especially during skinning) with infected wild rabbits and hares. In summer months, infection usually follows handling of other infected animals or birds or bites of infected ticks or other arthropods. Rarely, cases result from eating undercooked infected meat, drinking contaminated water, or mowing fields in endemic areas. In the Western US, ticks, deer flies, horse flies, and direct contact with infected animals are other sources of infection. Human-to-human transmission has not been reported. Laboratory workers are at particular risk because infection is readily acquired during normal handling of infected specimens.

Tularemia is considered a possible agent of bioterrorism because inhalation of as few as 10 organisms in the form of an aerosol can cause severe pneumonia.

In disseminated cases, characteristic focal necrotic lesions in various stages of evolution are scattered throughout the body. They are 1 mm to 8 cm in diameter and whitish yellow; they are seen externally as the primary lesions on the fingers, eyes, or mouth and commonly occur in lymph nodes, spleen, liver, kidneys, and lungs. In pneumonia, necrotic foci occur in the lungs. Although severe systemic toxicity may occur, no toxins have been demonstrated.

Symptoms and Signs of Tularemia

Onset of tularemia is sudden, occurring 1 to 10 (usually 2 to 4) days after exposure, with headache, chills, nausea, vomiting, fever of 39.5 to 40° C, and severe prostration. Extreme weakness, recurring chills, and drenching sweats develop. Clinical manifestations depend to some extent on the type of exposure (see table Types of Tularemia).

Within 24 to 48 hours, an inflamed papule appears at the site of exposure (finger, arm, eye, roof of the mouth), except in glandular or typhoidal tularemia. The papule rapidly becomes pustular and ulcerates, producing a clean ulcer crater with a scanty, thin, colorless exudate. Ulcers are usually single on the extremities but multiple in the mouth or eyes. Usually, only one eye is affected. Regional lymph nodes enlarge and may suppurate and drain profusely. A typhoid-like state frequently develops by the 5th day, and the patient may develop atypical pneumonia, sometimes accompanied by delirium.

Tularemia

Tularemia - Infectious Diseases - MSD Manual Professional Edition (1)Tularemia - Infectious Diseases - MSD Manual Professional Edition (2)

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In ulceroglandular tularemia, an inflamed papule appears on the finger or hand (top); it then rapidly becomes pustular and ulcerates, producing a clean ulcer crater with scanty, thin, colorless exudates (bottom).

Images courtesy of CDC/Dr. Brachman (top) and CDC/Emory Univ.; Dr. Sellers (bottom) via the Public Health Image Library of the Centers for Disease Control and Prevention.

Pneumonic tularemia can occur after inhalation or by hematogenous spread from another type of tularemia; it develops in 10 to 15% of ulceroglandular tularemia cases and in about 50% of typhoidal tularemia cases. Although signs of consolidation are frequently present, reduced breath sounds and occasional rales may be the only physical findings in tularemic pneumonia. A dry, nonproductive cough is associated with a retrosternal burning sensation. A nonspecific roseola-like rash may appear at any stage of the disease. Splenomegaly and perisplenitis may occur. In untreated cases, temperature remains elevated for 3 to 4 weeks and resolves gradually. Mediastinitis, lung abscess, and meningitis are rare complications.

Diagnosis of Tularemia

  • Cultures

  • Acute and convalescent serologic and polymerase chain reaction (PCR) testing

Diagnosis of tularemia is suspected based on a history of contact with rabbits, hares, or rodents or exposure to arthropod vectors, the sudden onset of symptoms, and the characteristic primary lesion and regional lymphadenopathy.

Patients should have cultures of blood and relevant clinical material (eg, sputum, lesions); routine cultures may be negative, and the laboratory should be notified that tularemia is suspected so that appropriate media can be used (and appropriate safety precautions ensured).

Acute and convalescent antibody titers should be done 2 weeks apart. A 4-fold rise or a single titer > 1:128 is diagnostic. The serum of patients with brucellosis may cross-react to F. tularensis antigens but usually in much lower titers. Fluorescent antibody or immunohistochemical staining is used by some laboratories. PCR testing can provide a rapid diagnosis.

Leukocytosis is common, but the white blood cell count may be normal with an increase only in the proportion of polymorphonuclear leukocytes.

Because this organism is highly infectious, samples and culture media from patients suspected of having tularemia should be handled with extreme caution and, if possible, processed by a high-level biosafety containment-equipped laboratory with a level 3 rating.

Prognosis for Tularemia

Case fatality is almost nil in treated cases and about 6% in untreated cases of ulceroglandular tularemia. Case fatality rates are higher for type A infection and for typhoidal, septicemic, and pneumonic tularemia; they are as high as 33% for untreated cases. Death usually results from overwhelming infection, pneumonia, meningitis, or peritonitis. Relapses can occur in inadequately treated cases. One attack confers immunity.

Treatment of Tularemia

The preferred drug is

Continuous wet saline dressings are beneficial for primary skin lesions and may diminish the severity of lymphangitis and lymphadenitis. Surgical drainage of large abscesses is rarely necessary unless therapy is delayed.

In ocular tularemia, applying warm saline compresses and using dark glasses give some relief. In severe cases, 2% homatropine 1 to 2 drops every 4 hours may relieve symptoms.

Intense headache usually responds to oral analgesics.

Prevention of Tularemia

When entering endemic areas, people should use tick-proof clothing and repellents. A thorough search for ticks should be done after leaving tick-infested areas. Ticks should be removed at once (see sidebar Tick Bite Prevention).

When handling rabbits, hares, and rodents, especially in endemic areas, people should wear protective clothing, including rubber gloves and face masks, because organisms may be present in the animal and in tick feces on the animal’s fur. Wild birds and game must be thoroughly cooked before eating.

Water that may be contaminated must be disinfected before use.

Key Points

  • F. tularensis is a highly infectious organism; in the US and Canada, the main reservoir is wild rabbits, hares, and rodents.

  • Tularemia can be acquired in many ways, including direct contact with infected animals (particularly rabbits and hares) or birds, bites of infected arthropods, inadvertent contact with laboratory specimens, or, rarely, inhalation of an infectious aerosol or ingestion of contaminated meat or water.

  • Patients have a fever of 39.5 to 40° C and other constitutional symptoms (eg, headache, chills, nausea, vomiting, severe prostration) along with specific manifestations related to the organ affected; skin lesions and/or lymphadenitis are most common, and pneumonia may occur.

  • Diagnose using cultures of blood and relevant clinical material; acute and convalescent antibody titers, polymerase chain reaction (PCR) testing, and certain staining techniques may also be helpful.

  • Take appropriate precautions in endemic areas, including tick avoidance strategies, use of protective gear while handling rabbits, hares, and rodents, and thorough cooking of wild birds and game.

Tularemia - Infectious Diseases - MSD Manual Professional Edition (2024)

FAQs

Is tularemia an infectious disease? ›

Tularemia is a highly infectious disease you get from the bacterium F. tularensis. You can get it from bug bites, infected animals, contaminated water or food, and particles of bacteria in the air. Tularemia can affect your skin, eyes, throat, lungs and intestines.

Which of the following is the causative agent of tularemia multiple choice question? ›

Tularemia, also known as “rabbit fever,” is a disease caused by the bacterium Francisella tularensis.

What are the three types of tularemia? ›

There are several types of tularemia.
  • Ulceroglandular tularemia. This type is the most common. ...
  • Glandular tularemia. The lymph nodes become swollen and painful, but skin sores do not form.
  • Oculoglandular tularemia. ...
  • Oropharyngeal tularemia. ...
  • Typhoidal tularemia. ...
  • Pneumonic tularemia. ...
  • Septicemic tularemia.

What is the drug of choice for tularemia? ›

Medication Summary

Medical therapy in tularemia is directed at antibiotic eradication of the bacterium F tularensis. Streptomycin is the drug of choice (DOC) for this treatment; although less experience exists with other aminoglycosides, gentamicin also appears to be effective.

How is tularemia classified? ›

tularensis is classified as a Category A agent of bioterrorism because of its high infectivity, ease of dissemination, and its potential to cause severe disease. Anticipated mechanisms for dissemination include contamination of food or water and aerosolization.

Can you get tularemia from touching? ›

People can get tularemia by: Being bitten by a dog tick, lone star tick, wood tick, or deer fly with tularemia bacteria. Touching animal tissue with tularemia bacteria, most commonly when hunting or skinning infected rabbits, hares, muskrats, beavers, prairie dogs, and other rodents.

What is the main source of tularemia? ›

Tularemia is a potentially serious illness that occurs naturally in the United States. It is caused by the bacterium Francisella tularensis found in animals (especially rodents, rabbits, and hares).

How does tularemia affect the immune system? ›

tularensis tricks host cell mitochondria, which produce energy for the cell, in two different phases of infection. In the first eight hours of infection, the bacteria increase mitochondria function, which inhibits cell death and prevents the cell from mounting an inflammatory response to avoid an immune system attack.

What type of biological agent is tularemia? ›

Tularemia, a bacterial zoonosis, is caused by Francisella tularensis, one of the most infectious pathogenic bacteria known. It requires inoculation or inhalation of as few as 10 organisms to cause disease.

What are the first symptoms of tularemia? ›

Most cases of tularemia begin with rapid onset of nonspecific, flu-like symptoms including fever, chills, headaches, muscle pain (myalgia), joint pain (arthralgia), loss of appetite, and a general feeling of ill health (malaise). Additional symptoms may occur depending upon how a person is infected.

Can tularemia go away on its own? ›

There are no home remedies for tularemia. It is a relatively rare disease but can quickly become fatal (60% of individuals infected may die from it) if not treated with appropriate antimicrobials.

What kind of tick carries tularemia? ›

In the United States, ticks that transmit tularemia to humans include the dog tick (Dermacentor variabilis), the wood tick (Dermacentor andersoni), and the lone star tick (Amblyomma americanum).

What is the first-line treatment for tularemia? ›

Only aminoglycosides, tetracyclines and fluoroquinolones are considered in the first-line treatment of tularemia.

How is tularemia spread? ›

How do people get tularemia? People and animals most commonly get tularemia from a bite by an infected tick or fly, or following contact with an infected animal . Tularemia can be spread to humans from infected pets or wildlife, but is not spread person to person.

What are the long term effects of tularemia? ›

Hematogenous spreading and complications such as systemic disease, pneumonia, formation of abscesses and lymph node suppurations can be seen in relation to all forms of infection. Thus, tularemia can be a prolonged and debilitating disease especially in cases of delayed treatment [2,4].

Can someone become infected with the tularemia bacteria from another person? ›

Tularemia is not known to be spread from person to person. People who have tularemia do not need to be isolated. People who have been exposed to the tularemia bacteria should be treated as soon as possible. The disease can be fatal if it is not treated with the right antibiotics.

What category is tularemia bioterrorism? ›

Tularemia is an occupational risk for farmers, foresters, and veterinarians, and is listed by the U.S. Centers for Disease Control and Prevention (CDC) as one of the six category A, or high-priority, biological warfare agents.

Is tularemia a tick borne disease? ›

Tularemia is a rare disease caused by the bacterium Francisella tularensis. It can be spread to people through the bite of an infected American Dog Tick (Dermacentor variabilis) or Lone Star tick (Amblyomma americanum), the bite of an infected deer fly, or contact with tissues of an infected animal.

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