Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Lyme disease is the most important vector-borne disease infecting over 400,000 Americans through tick bites each year. The blacklegged tick (Ixodes scapularis) is the vector that transmits the causative pathogen to humans. The lack of effective and affordable tick control products is among major challenges for the existing tick control and Lyme disease prevention strategies in the United States. USDA ARS scientists led a research team including industry researchers to evaluate potential of an existing veterinary acaricidal compound, Ivermectin, for use to develop a new mouse bait formulation targeting ticks feeding on mice to break the life cycle of this disease vector in nature. The acaricidal properties of ivermectin were evaluated using an artificial blood feeding technique followed by animal trials designed to determine tick control efficacy of ivermectin at different serum concentrations. The study determined the lethal concentrations of ivermectin against adult and immature stages of the blacklegged tick. Results also revealed that orally delivered ivermectin was metabolized rapidly in mice. Further evaluation of the performance of ivermectin-based mouse bait may be necessary before its utility as a valid host-targeted tick control tool can be decided. Pest control companies and tick control researchers will benefit from the data and knowledge generated from this study.

Technical Abstract: The lack of effective and affordable new host-targeted tick control products is among major challenges for the existing control strategies against the blacklegged tick, Ixodes scapularis, the vector of Lyme disease affecting public health in the United States. The goal of this study was to assess acaricidal properties of orally delivered ivermectin against the blacklegged tick, Ixodes scapularis, for development of new mouse bait formulation to control immature stages of the blacklegged tick. Female ticks capillary-fed with rabbit blood containing 300 and 600 ppb demonstrated a significantly higher mortality starting at 72 h after the start of capillary feeding. Such Ivermectin concentrations also significantly reduced blood feeding of the females, as determined by female excretion and engorgement scores. Nymphal capillary feeding experiments were unsuccessful as nymphal in all treatment groups died like in the control group, likely due to desiccation. In the mouse trials, ivermectin reached peak serum concentrations, 650 ppb and 6715 ppb, respectively at 2 hours after consumption of a single treated pellet containing 80 µg and 160 µg ivermectin by mice but was rapidly depleted from mouse blood with a half-life less than six hours. When mice were infested with nymphal and larval ticks at different times relative to mice’s access to diet pellets containing ivermectin (48 ppm) ad libitum, a 45.5% to 100% reduction in the number of blood-fed nymphs and larvae was observed in the treatment groups in comparison to ticks fed on untreated mouse pellets. Further laboratory and field studies are necessary to validate the utility of ivermectin-based mouse-targeted tick control products.