The image, taken with a fluorescent microscope, shows mouse macrophages (red) 12 hours after infection with a virulent strain of Francisella tularensis (stained green). The cells on the left are untreated, while the cells on the right were treated 3 days in advance with CLDC+MPF. The untreated cells fail to control replication of Francisella tularensis. In contrast, cells activated with the CLDC+MPF therapeutic have nearly eliminated all of the bacteria. Francisella tularensis is a pathogenic species of gram-negative bacteria and the causative agent of tularemia or rabbit fever. Due to its ease of spread by aerosol and its high virulence, F. tularensis is classified as a Class A agent by the U.S. government. 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.