Tularemia

Zoonosis UpdateI know of no other infection of animals communicable to man that can be acquired from sources so numerous and so diverse.In short, one can but feel that the status of tularaemia, both as a disease in nature and of man, is one of potentiality.-R. R. Parker, 1934 1 1934 BackgroundTularemia, also known as rabbit fever and deerfly fever, is a bacterial zoonosis caused by the small, pleomorphic, gram-negative coccobacillus Francisella tularensis.The organism can infect numerous species of animals; in the United States, rodents and lagomorphs are the important epizootic hosts, and various species of ticks are important maintenance hosts and biologic vectors.Of 4 biogroups of the organism, 2 account for most clinical disease; these biogroups can be distinguished biochemically, epidemiologically, and by virulence testing.Jellison type A (F tularensis subsp tularensis) ferments glycerol, is highly virulent for laboratory rabbits, and is found predominately in North America; Jellison type B (F tularensis subsp holarctica, formerly susbsp palaearctica), which is less virulent than type A, is found throughout Europe and Asia but also in North America.Francisella tularensis subsp mediaasiatica is not known to cause infections in humans and is found in Central Asia.Francisella novicida was previously considered a separate species but is now classified as another biogroup of F tularensis.Francisella tularensis subsp novicida is of low virulence 2 and has been isolated from human patients with a tularemia-like illness in the United States and Canada.3 Tularemia was first described by McCoy in 1911 as a plague-like illness of California ground squirrels.In 1912, McCoy and Chapin 4 published a paper on the syndrome and the causative agent, which was originally called Bacterium tularense after Tulare County, where the work was done.The first described clinical case in which F tularensis was implicated as the etiologic agent occurred in 1914, when the oculoglandular form was reported in a restaurant worker in Cincinnati. 5 Edward Francis, a US Public Health Service surgeon, dedicated much of his scientific career to research on the organism, including classifying the various clinical manifestations of the disease, cultivating the organism, devel-oping serologic tests, and elucidating its various mechanisms of transmission.In 1947, the agent was renamed Francisella tularensis in his honor.