Integrated Control of Nymphal Ixodes scapularis: Effectiveness of White-Tailed Deer Reduction, the Entomopathogenic Fungus Metarhizium anisopliae, and Fipronil-Based Rodent Bait Boxes.

Pathogens transmitted by ticks are the leading cause of arthropod-associated human diseases in the United States and managing the risk of exposure to potentially infected ticks is of vital public health importance. A 3-year integrated tick management program to control blacklegged ticks, Ixodes scapularis, the primary vector for the pathogenic agents of Lyme disease, human anaplasmosis, and babesiosis, was implemented in the town of Redding in southwestern Connecticut beginning in 2013. Combinations of white-tailed deer, Odocoileus virginianus, reduction, area application of the entomopathogenic fungus Metarhizium anisopliae, and fipronil-based rodent bait boxes were evaluated for their ability to reduce nymphal I. scapularis over 3 years. Interference from local hunters prevented sufficient, sustained deer removal previously reported to negatively impact I. scapularis abundances (i.e., <5 deer/km2). The combination of fipronil-based bait boxes and broadcast application of M. anisopliae had the most impact of any treatment combination; questing nymphs were reduced 78-95% within each year and Borrelia burgdorferi-infected questing nymphal I. scapularis encounter potential was reduced by 66% as compared with no treatment in the third year of the study. A combination of the broadcast application of M. anisopliae and small rodent-targeted fipronil-based bait boxes is an effective low-toxicity integrated approach that significantly reduced encounters with B. burgdorferi-infected questing nymphal I. scapularis on individual properties.