Francisella Tularensis - Pathogenesis

Pathogenesis

F. tularensis has been reported in birds, reptiles, fish, invertebrates and mammals including humans. Despite this, no case of tularemia has been shown to be initiated by human-to-human transmission. Rather, tularemia is caused by contact with infected animals or vectors such as ticks, mosquitos, and deer flies. Reservoir hosts of importance can include lagomorphs, rodents, galliform birds and deer.

Infection with F. tularensis can occur via several routes. The most common occurs via skin contact, yielding an ulceroglandular form of the disease. Inhalation of bacteria - particularly biovar tularensis, leads to the potentially lethal pneumonic tularemia. While the pulmonary and ulceroglandular forms of tularemia are more common, other routes of inoculation have been described and include oropharyngeal infection due to consumption of contaminated food and conjunctival infection due to inoculation at the eye.

F. tularensis is capable of surviving outside of a mammalian host for weeks at a time and has been found in water, grassland, and haystacks. Aerosols containing the bacteria may be generated by disturbing carcasses due to brushcutting or lawn mowing; as a result, tularemia has been referred to as lawnmower disease. Recent epidemiological studies have shown a positive correlation between occupations involving the above activities and infection with F. tularensis.