Controlling Ticks and Tick-borne Zoonoses with Biological and Chemical Agents

Ticks are important vectors of disease-causing pathogens of humans, wildlife, and livestock. Reducing tick abundance is an important but elusive goal. Chemical pesticides applied to habitats occupied by ticks can be effective but appear to have significant negative effects on nontarget organisms. Devices that apply insecticides directly to vertebrate hosts for ticks reduce nontarget effects, and recent field tests support their effectiveness, but securing the devices and avoiding food subsidies to tick hosts remain significant challenges. Recent research has identified several types of organisms that show potential as biological control agents for ticks. Probably the most promising are the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana, which laboratory studies indicate are often highly lethal to several different tick species at multiple life stages. The few field tests undertaken show somewhat weaker impacts on tick survival, but suggest that the effectiveness of these fungi in controlling ticks could be enhanced by (a) identifying or selecting for highly lethal strains; (b) applying fungal spores directly to vertebrate hosts for ticks; and (c) optimizing the dose, delivery medium, and seasonal timing for environmental deployment. Thus both host-targeted chemical control and biocontrol of ticks show much promise, and would benefit from further research.