Tularemia is a zoonotic disease caused by the Gram-negative coccobacillus Francisella tularensis, which was first isolated from rodents in 1911 in Tulare County, California, USA. Tularemia has been found in more than 250 animal species. F. tularensis strains have been identified as belonging to several subspecies including tularensis (also known as type A or subspecies nearctica), palaearctica (also known as type B or subspecies holarctica), mediasiatica, and novicida. This classification has been done principally on the basis of virulence, citrulline ureidase activity, and acid production from glycerol. Subspecies holarctica is now the more widely used terminology in place of subspecies palaearctica. Type A is reported to have a terrestrial cycle with the main reservoirs being cottontail rabbits (Sylvilagus spp) and ticks. Type B is reported to have a mainly water-borne cycle with aquatic rodents as reservoirs. These rodents include muskrats (Ondatra zibethicus) and beavers (Castor canadensis) in North America, and ground voles (Arvicola terrestris) in the former Soviet Union. However, it is not clear whether these animal species are the true reservoir of the bacterium in the environment. Type A is considered more virulent than type B for humans. 1, 2 and 3