Control of Lyme borreliosis in Sweden by reduction of tick vectors: An impossible task?

Abstract

During the last decade, much research on control strategies against the primary vector, Ixodes scapularis, of Lyme disease in northeastern USA has been carried out. This has included work on biological or chemical control, habitat modification, and reduction of host availability. In this paper we evaluate the possibility of using these methods for control of the primary vector of Lyme borreliosis in Sweden, I. ricinus. It is emphasized that in Sweden people mainly contract Lyme borreliosis in woodlands and forests. Because of the enormous size of the area that would need treatment, general application of acaricides and habitat modification may not work well in Sweden. Another possible method is to reduce the availability of tick hosts. This method can be targeted at species that are essential for tick reproduction or at hosts that are capable of infecting ticks with Borrelia burgdorferi. On isolated Swedish islands where few mammal species are present, reduction of the main or only reservoir host may effectively control Lyme borreliosis. On the Swedish mainland, however, at least four common mammal species are important blood-hosts to female I. ricinus, and at least eight common mammal species are competent reservoirs for B. burgdorferi. Sufficient reduction of host availability may therefore not be achieved here without killing vast numbers of mammals. In general in Sweden, the most effective method of preventing Lyme borreliosis seems to be to inform people about how to dress in risk areas, and that daily checks for ticks with prompt removal of attached ticks drastically reduces the infection risk.