What is Tularemia?
Tularemia is an uncommon infection caused by the bacterium Francisella tularensis. It occurs throughout the world and used to be quite common in the United States. The organism infects many different animals, including humans, cats, rabbits and a variety of small mammals.
The bacterium is transmitted through the bites of infected ticks or other arthropods (a group of animals that includes insects, ticks and mites). Although people are more likely to become infected from the bite of a tick -- a variety of ticks can spread the infection -- they can also contract the disease through contact with contaminated animals and animal products. Some individuals acquire the infection while skinning infected rabbits and squirrels or when they are scratched by a cat or other carnivore carrying the organisms on its claws. People can also become infected if they drink contaminated water, eat inadequately cooked meat or inhale particles containing the bacterium.
How is it diagnosed?
The initial signs of tularemia infection vary, depending on the site of infection. When the bacteria enter through the skin, an ulcer (open sore) forms and lymph nodes in the area become enlarged. Sometimes the swollen lymph nodes are present but no skin lesion can be found. In either case, high fever is a prominent feature of the infection. While the infection can last weeks and the patient can become quite ill, recovery is the rule. The eye is another point of entry for the organism, and the infection can cause a variety of eye problems (such as conjunctivitis, inflammation of the membrane lining the eyes and eyelids), along with redness and swelling in nearby lymph nodes.
Sometimes, patients with tularemia have fever and signs of sepsis (severe widespread infection), but no enlarged lymph nodes. In such cases, the infection is especially difficult to diagnose and is sometimes confused with typhoid fever.
How is it treated?
Tularemia is treated with antibiotics until four to five days after the fever subsides. Treatment of pneumonia is supportive in nature. In severe cases, corticosteroids may be used to reduce inflammation.
What might complicate it?
The major clue to all of the illnesses caused by F. tularensis is a history of animal exposure. The infection can result in pneumonia, pericarditis, or osteomyelitis, due to spread through the blood. Only rarely are there serious complications such as meningitis (infection of the meninges, the tissues lining the brain and spinal cord), encephalitis (a severe infection of the brain), or myocarditis (infection of the heart muscle).
The prognosis for tularemia is good with rapid diagnosis and antibiotic treatment, resulting in full recovery. If the infection is left untreated, prognosis worsens and can become grave, especially in immunocompromised individuals.
Tularemia needs to be distinguished from infections such as pyoderma, cat-scratch disease, brucellosis, plague, anthrax, infectious mononucleosis, and other bacterial and fungal diseases that invade the lungs, gastrointestinal tract, and skin.
Infectious disease specialist, pulmonary disease specialist and dermatologist.
Last updated 11 July 2021