Among the various species of hard ticks, Ixodes ricinus is the most frequently 
found tick throughout Europe. As with other ixodid ticks, the developmental 
cycle runs through three stages. In each stage a blood meal is required in order 
to develop to the next stage. Ixodes ricinus has been found to feed on more than 
300 different vertebrate species. Usually, larval ticks feed on small mammals 
such as mice and become infected with various microorganisms and viruses, of 
which some are substantial pathogens to humans. The pathogens remain in the tick 
during molting and are thus transstadially transmitted to the next developmental 
stage. Pathogens transmitted to humans are the agents of Lyme borreliosis, the 
tick-borne encephalitis virus, Rickettsia species, Anaplasma phagocytophilum, 
occasionally Francisella tularensis, and protozoal Babesia species. Within the 
scope of an EU project Ixodes ricinus ticks from all federal states of Austria 
were searched by means of PCR methods for bacterial pathogens such as Anaplasma 
phagocytophilum, Borrelia burgdorferi sensu lato, Coxiella burnetii, Ehrlichia 
spp., Francisella tularensis, Rickettsia spp., and protozoal Babesia. 
Additionally, the prevalence of Bartonella spp. in this tick species was also 
determined. Besides the singular detection of Coxiella burnetii and Francisella 
tularensis in one tick collection site the overall prevalence of Anaplasma 
phagocytophilum, borreliae, rickettsae and babesiae in Ixodes ricinus amounted 
to 15%, 14%, 6% and surprising 36% and 51%, respectively. Bartonellae were 
detected in about 7%.