The impact of deer exclusion fencing on host-seeking blacklegged ticks on suburban residential properties in southern New England

Recommendations to use deer-excluding fencing as a method to reduce blacklegged ticks (Ixodes scapularis Say) in residential settings are based primarily upon studies excluding deer from large areas (≥3.5 hectares), often in undeveloped woodland settings. Evidence is still needed on the efficacy of deer-excluding fences for tick management at smaller suburban residential properties common to tick-endemic areas of the northeastern United States. We measured I. scapularis abundance at 16 fenced and 16 unfenced properties in Fairfield County, Connecticut, Westchester County, New York, and Washington County, Rhode Island. Overall, adult and nymphal I. scapularis encounter rates (ticks per sampling meter) were slightly higher on unfenced properties compared to within fenced properties, but differences were not significant (P > 0.05). Among fenced properties alone, tick encounter rates were significantly higher in areas immediately outside of fences compared with inside of fences for nymphs (P = 0.005), but not for adults (P > 0.05). Prevalence of tick pathogen infection with Borrelia burgdorferi sensu stricto, Borrelia miyamotoi, Babesia microti, Babesia odocoilei, or Anaplasma phagocytophilum did not differ significantly between fenced and unfenced properties (P > 0.05). Irrespective of fencing, adult tick abundance was higher at properties with stonewalls, dense herbaceous ecotone vegetation, and an absence of bird feeders. Nymphal tick encounter rates were associated with stonewalls, an absence of bird feeders, and presence of dense herbaceous understory vegetation. Household survey data revealed that deer were observed within some fenced areas. Our findings do not provide strong evidence that deer-excluding fences at properties smaller than 3.5 hectares surpress blacklegged ticks.