Comparative behavior of different life-cycle stages of Ixodes ricinus (Acari: Ixodidae) to human-produced stimuli.

Nymphs of Ixodes ricinus (Linnaeus, 1758), I. scapularis Say, 1821, and I. pacificus Cooley & Kohls, 1943 are epidemiologically the most dangerous stage for transmission of Lyme disease to humans. Many factors play a role in the epidemiological significance of the nymphs. In this study, we address the question of whether nymphs show a greater tendency than adults to accept humans as their host. To evaluate this, we have compared the host acceptance behavior of nymphs and adults (males and females) with respect to a human in Rambouillet forest, a focus of Lyme disease. Individual ticks (nymph, male or female) located on a herbaceous stem were exposed to different stimuli (e.g., approach, stem movement, breathing), and the response of each individual to these stimuli was noted. Tick responses were categorised into classes (from 0 to 3) according to their intensity. Statistical analysis carried out on 22 ticks allowed us to compare the behavior of the nymph stage with respect to males and females. Despite the small sample sizes, it appears that nymphs are more responsive to a human than are the adults.