Abstract:
The mainstream forestry policy in many European countries is to convert coniferous plantations into (semi-natural)
deciduous woodlands. However, woodlands are the main habitat for Ixodes ricinus ticks. Therefore, assessing to what extent
tick abundance and infection with Borrelia spirochetes are affected by forest composition and structure is a prerequisite for
effective prevention of Lyme borreliosis. We selected a total of 25 pine and oak stands, both with and without an abundant
shrub layer, in northern Belgium and estimated tick abundance between April and October 2008–2010. Additionally, the
presence of deer beds was used as an indicator of relative deer habitat use. Borrelia infections in questing nymphs were
determined by polymerase chain reactions. The abundance of larvae, nymphs, and adults was higher in oak stands compared
to pine stands and increased with increasing shrub cover, most likely due to differences in habitat use by the ticks’ main
hosts. Whereas tick abundance was markedly higher in structure-rich oak stands compared to homogeneous pine stands, the
Borrelia infection rates in nymphs did not differ significantly. Our results indicate that conversion towards structure-rich
deciduous forests might create more suitable tick habitats, but we were unable to detect an effect on the infection rate.
