Francisella tularensis is a pathogenic species of gram-negative
bacteria. A member of the genus Francisella, F. tularensis is the
causative agent of tularemia or rabbit fever. F. tularensis is
capable of infecting a number of small mammals such as voles,
rabbits, and muskrats, as well as 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 and mosquitos.