Monitoring of acaricide resistance in Rhipicephalus bursa ticks collected from sheep on the island of Lesvos, Greece.

Abstract

Chemical acaricides are widely used to control ticks on animals to avoid heavy tick burdens, which cause economic loses. In tick populations certain individuals are more tolerant for a specific acaricide than other individuals. Previous studies have shown that continued exposure to an acaricide results in removal of the susceptible part of a tick population and an increase in the proportion of resistant individuals. Tick control strategies in Greece rely heavily on synthetic pyrethroids. Therefore, this study was designed to test the susceptibility of Rhipicephalus bursa ticks, collected from sheep of the island Lesvos, for the synthetic pyrethroid, alpha-cypermethrin. The Larval Packet Test was carried out for definitive confirmation of a diagnosis of resistance. For Rhipicephalus bursa ticks, the lethal concentration (LC) to kill 50% of the ticks was 3,816 · 10-3 mg/mL alpha-cypermethrin. In future studies, this LC50 can be used as a baseline to compare and/or confirm the resistance status of field populations of Rhipicephalus bursa ticks. It is recommended to closely monitor possible changes in susceptibility to acaricides at an early stage in order to adapt the tick control policies. Additional baseline data are required for other ticks found on livestock in Greece using the same methods employed in this study.