Does Experimental Reduction of Blacklegged Tick (Ixodes scapularis) Abundance Reduce Lyme Disease Incidence?

Controlling the abundance of blacklegged ticks is considered the foundation for the prevention of human exposure to pathogens transmitted by these vectors in eastern North America. The use of broadcast or host-targeted acaricides is generally found to be effective at reducing the local abundance of ticks. However, studies that incorporate randomization, placebo controls, and masking, i.e., blinding, generally find lower efficacy. The few studies that include measurements of human-tick encounters and cases of tickborne disease have not shown impacts of acaricidal treatments. We compile literature on relevant studies from northeastern North America to address possible causes for discrepancies in study outcomes and suggest possible mechanisms that could underlie the diminished efficacy of tick control in reducing cases of tickborne disease in people.

Automated summary

Controlling the abundance of blacklegged ticks through acaricides has been found to be effective, but studies with randomization, placebo controls, and blinding show lower efficacy. Studies measuring human-tick encounters and tickborne disease cases have not shown impacts of acaricidal treatments. This literature review explores possible causes for discrepancies in study outcomes and discusses potential mechanisms for the diminished efficacy of tick control in reducing tickborne disease cases in people.