SEASONAL VARIATION IN THE INFESTATION OF RODENTS WITH IXODES RICINUS (ACARI: IXODIDAE) AND PREVALENCE OF INFECTION WITH BORRELIA BURGDORFERI IN A RECREATION AREA

Abstract:
In woodlands of Western Europe, rodents like yellow-necked mice (Apodemus flavicollis Melchior) or bank voles (Clethrionomys glareolus Schreber) play an important role in the natural circulation of B. burgdorferi sensu lato. It was possible to catch a total number of 120 small mammals (only first capture) of four species, among them 62 voles and 52 mice and both were shown parasitized by uninfected and infected Ixodes ricinus immatures. The infestation of small mammals with larvae was highest in June and lowest in July/August. Our study also showed that the level of infestation with I. ricinus was lower in bank voles than in mice. The seasonal patterns of peak infestation by I. ricinus on Apodemus were bimodal with peaks in June and September. In contrast, voles showed a unimodal activity pattern with the highest larvae numbers in June. In general, the maximal abundance of larvae on rodents was observed in June. The infection rate of engorged larvae increased from spring to autumn. This behaviour was also detectable in questing nymphs of the same study area. Compared to A. flavicollis, bank voles had both a lower mean number of infesting larvae and a lower number of infected animals. The spirochetal agent of Lyme borreliosis occurred endemically in the study area, with Apodemus flavicollis being mainly participating when both investigated species of small mammals were compared. There is a high infection risk for men in the investigated recreation area. Due to the course of prevalence, the infection risk seems to be highest in summer and autumn.