Francisella tularensis, the causative agent of the zoonotic disease tularaemia, is highly contagious and potentially fatal for a wide range of wildlife species of the northern hemisphere, also humans. Although recognized as a pathogen for over 100 years, much still remains to be elucidated concerning the ecology and transmission of the bacterium, hence this literature overview aims at compiling data regarding the aquatic association and the role of mosquitoes in transmission of Francisella tularensis subspecies holartica, the sole subspecies in Sweden. While a linkage between the bacterium and natural waters stands beyond dispute, there is no consensus in the literature concerning its potential as a reservoir. However, two prevailing theories can be distinguished; one proposes the water association being mammaldependent and thus merely the result of contamination from semi-aquatic mammals living in close vicinity to the water source. The other, quite contrary, suggests mammal-independence and hence that water, possibly in association with protozoa, serves as an environmental reservoir for the bacterium.

This thesis aims to analyse relations between the risk of Francisella in endemic areas and environmental variables. The thesis also discusses relations between occurrences of Tularemia and meteorological factors. The analysis resulted in several significant models that explained the occurrence of Francisella. These models can however only be applied to the year 2004 since there were too few test performed the other years, therefore no comparisons could be made. Another conclusion was that the relative humidity was significally higher in the year 2003, the same year as the occurrences of Tularemia was at its peak. .