Figure 1

I. ricinus life cycle. I. ricinus is a three-host tick of which each stage, i.e. larva, nymph and adult female (adult males may take a small blood meal but do not fully engorge), feeds on a different vertebrate host. I. ricinus ticks parasitize a wide range of hosts, i.e. more than 300 different vertebrate species [9]. Immature ticks particularly infest rodents such as Apodemus flavicollis, Myodes glareolus and Sciurus vulgaris [32,70-73]. Immature ticks also feed on ground-foraging birds (such as Turdus spp), lizards and artiodactyls [9,74]. Adults mainly feed on larger mammals, but are usually outnumbered by immature ticks on such hosts [75]. I. ricinus does not show host specificity and the most important determinants of host choice are host habitat and behaviour, microclimate conditions [32], and questing height of the different tick stages. Larvae and nymphs usually stay closer to the ground, i.e. they are predominantly observed between 0 to 30 cm and 30 to 70 cm, respectively [76,77], probably because they are more sensitive to ambient humidity than mature stages due to their high surface area to volume ratio [32]. Male and female adults are observed higher up on the vegetation, usually 60 to 80 cm above the ground, but they may be found higher than 1.5 m depending on the surrounding vegetation [76,77] (Tick pictures by N. Tonetti; Host pictures by P.-F. Humair and L. Gern).