How Can Forest Managers Help To Reduce The Risk For Lyme Borreliosis?

In the northern temperate zone, the highest Ixodid tick densities are found in forests. However, tick densities and Borrelia prevalence strongly vary from one forest location to another. Multiple drivers underlie this variability. In this chapter we provide more information on the way forest managers can influence three important risk determining factors, notably forest stand composition and structure, visitor rates and the probability that visitors come in contact with questing ticks. Using a simple probabilistic model, we demonstrate that guidance of visitor flows in forests combined with a trail management that focuses on reducing the contact probability with questing ticks appear to be the most effective risk reducing measures. Densities of infected nymphs vary between forest types, but the differences are too small to significantly affect Lyme borreliosis risk. Altering the forest composition through changing the dominant tree species or the forest structure should therefore not be the primary focus of risk management. However, forest type also affects the Borrelia genospecies community composition and a forest type-dependent prevalence of more or less pathogenic genospecies deserves more attention in risk assessments.