Tularemia is a rare but highly infectious disease that resides in small mammals such as rodents and rabbits, and arthropods, such as ticks. The disease is caused by the bacterium Francisella tularensis. Tularemia is most often transmitted to humans by tick or biting fly bite, handling of an infected animal, or inhalation or ingestion of the bacterium. People have not been known to transmit the infection to others. The severity of tularemia varies greatly. Some cases are mild and self-limiting; others may have serious complications, and a small percentage (about 2 percent) are fatal.
The symptoms of tularemia vary greatly among affected individuals. Some individuals may have no apparent symptoms (asymptomatic); others can develop serious complications affecting several organ systems with potentially life-threatening complications. After infection, the period of time it takes symptoms to appear (incubation period) is usually three to five days, but may take as long as two to three weeks.
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. Infection through skin (e.g., tick bite or handling of infectious matter) may result in an ulcer or rash on the skin at the point of infection and swollen, painful lymph nodes (lymphadenopathy). These cases may be referred to as ulceroglandular tularemia. In some cases, individuals will have lymphadenopathy without any skin symptoms. These cases are referred to as glandular tularemia. Ulceroglandular and glandular tularemia account for more than 75 percent of cases.
Infection through breathing in (inhalation) the bacterium may result in infection of the lungs (pneumonia), a collection of fluid around the lungs (pleural effusion), and lung abscesses. These cases are referred to as pneumonic tularemia. Eating undercooked, infected animal meat may result in sore throat, nausea, vomiting, diarrhea, and abdominal pain. In rare cases, gastrointestinal bleeding may occur. These cases are referred to as oropharyngeal tularemia.
Tularemia can also affect the eyes resulting in inflammation of the delicate membrane that lines the eyes (conjunctiva), a condition called conjunctivitis. Conjunctivitis can cause pain, redness, and itching of the eyes. Nearby lymph nodes may be swollen and painful. These cases are referred to oculoglandular tularemia.
Some individuals may develop the typhoidal form of tularemia in which fever, myalgias, and general ill health (malaise) develop without accompanying skin lesions or lymphadenopathy. Because of the lack of obvious symptoms, this form of tularemia is difficult to diagnose.
Tularemia has the potential to affect various organ systems of the body including the central nervous system, heart, and liver resulting in inflammation of the membranes surrounding the brain and spinal cord (meningitis), inflammation of the lining of the heart (endocarditis), and inflammation of the liver (hepatitis). Additional serious complications potentially associated with tularemia include infection of the blood (sepsis) and infection of various bones (osteomyelitis).
Tularemia is caused by the bacterium Francisella tularensis. Most cases occur from being bitten by flies or ticks carrying the disease or from exposure to animals infected with the bacteria.
Tularemia has been found in >100 animal species including rabbits, muskrats, squirrels and beavers. Handling infected animal tissue (e.g., skinning or dressing animal carcasses) or eating insufficiently cooked meat from an infected animal may result in tularemia. Domestic pets such as dogs and cats can be responsible for transmitting tularemia to humans as well. Dogs and cats may come in contact with infected animals or ticks and may spread the disease to humans through their saliva or claws.
Tularemia may be also transmitted through the air by breathing in (inhalation) of aerosolized bacteria. Common activities including cutting brush or mowing lawns can aerosolize the bacteria from the environment and cause infection in humans.
Francisella tularensis is an extremely resilient bacterium and able to survive in the environment (e.g., mud, water, or decaying animal carcasses) for weeks and, rarely, direct contact or ingestion of contaminated materials including water or soil may cause tularemia.
No cases of human-to-human transmission have been documented in the medical literature.
Tularemia has gained more attention in recent years because of its potential for use in biological warfare.
Tularemia affects males and females, although the majority of cases are males, probably because of greater outdoor exposure opportunities. The disease is rare in the United States with approximately 100-200 new cases reported each year. Some researchers believe that many cases of tularemia often go unreported or misdiagnosed, making it difficult to determine the true frequency of this disease in the general population.
Although tularemia can occur anywhere in the United States, more than half of the cases reported each year occur in rural areas of Arkansas, Missouri, Oklahoma, and Kansas. Tularemia may be found in all parts of Europe and Asia with greater frequency in Siberia and Scandinavian countries.
In Japan, tularemia may be known as yato-byo or Ohara’s disease, after Dr. Ohara who first described a rabbit-associated febrile disease.
A diagnosis of tularemia is made by a thorough clinical evaluation, a detailed patient history, and a variety of tests that may include an attempt to isolate the bacteria from blood or body tissue or through specialized blood tests (serologic tests) that measur. the body's immune system response against the bacterium.
Tularemia is treated with antibiotics. Antibiotics such as doxycycline and Ciprofloxacin can be effective and can be taken by mouth (orally). In severe cases, streptomycin or gentamicin can be given by injection into a muscle or vein.
Other treatment is symptomatic and supportive.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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Research on infectious diseases such as tularemia is ongoing. For more information about these disorders, contact the World Health Organization (WHO) listed in the Resources section below.
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