Tularemia pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Francisella tularensis is an extremely infectious bacteria; fewer than ten organisms can cause disease leading to severe illness. The bacteria penetrate into the body through damaged skin and mucous membranes, or through inhalation. Francisella tularensis is an intracellular bacterium, meaning that it is able to live as a parasite within host cells. It primarily infects macrophages, a type of white blood cell. It is thus able to evade the immune system. The course of disease involves spread of the organism to multiple organ systems, including the lungs, liver, spleen, and lymphatic system.

• Bacteremic phase initiates the spread of disease into reticuloendothelial tissue.
• This evokes an immunological reaction resulting in a flurry of tumor necrosis factor alpha, interleukin-10 and 12, as well as IFN-gamma.
• T-cells become involved as the disease progresses.
• Studies show that T-cells are necessary in stopping the reaction, but not controlling it.
• A successful tularemia infection is the ultimate result of the disease’s ability to survive within macrophage host cells. ^[1]

• Francisella tularensis is one of the most infectious bacteria known; fewer than ten organisms can cause disease leading to severe illness.
• The bacteria penetrate into the body through damaged skin and mucous membranes, or through inhalation.
• Humans are most often infected by tick bite or through handling an infected animal.
• Ingesting infected water, soil, or food can also cause infection. ^[2]
• Tularemia can also be acquired by inhalation; hunters are at a higher risk for this disease because of the potential of inhaling the bacteria during the skinning process.
• Tularemia is not spread directly from person to person.
• Francisella tularensis is an intracellular bacterium, meaning that it is able to live as a parasite within host cells.
• It primarily infects macrophages, a type of white blood cell. It is thus able to evade the immune system.
• The course of disease involves spread of the organism to multiple organ systems, including the lungs, liver, spleen, and lymphatic system. ^[1]

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