Francisella tularensis: an Overview

F rancisella tularensis was first isolated in 1912 from rodents suffering from a plague-like disease in Tulare County, Calif. Subsequently, investigators learned that this small, gram-negative bacterium infects many animal species and is associated with a wide range of diseases. In humans, the bacterium causes a serious, sometimes fatal disease, called tularemia, which is also known as rabbit fever, hare fever, deerfly fever, or lemming fever. Tularemia in humans occurs in many countries in the Northern but not the Southern Hemisphere. The reason for this distribution is not known. Terrestrial and aquatic mammals such as ground squirrels, rabbits, hares, voles, muskrats, water rats, and other rodents are thought to serve as reservoirs for this disease. In particular, increases in rodent tularemia are closely linked to epidemic outbreaks of human tularemia. Additionally, F. tularensis survives in amoebae, a finding that appears to explain the association of this bacterium with waterways. Although our understanding of F. tularensis is limited, ongoing research is elucidating its pathogenesis and virulence mechanisms. Researchers who are sequencing the genomes of the Schu S4 and LVS strains expect to complete these projects soon, and information from them is already providing valuable insights. In parallel, large-scale microarray and proteomic analyses are being used to identify differences among these and other strains. Such information will surely prove valuable for developing new diagnostic, prophylactic, and therapeutic agents for F. tularensis. F. tularensis Has Few Close Relatives