Assessing the Repeatability of Tick Dragging as a Method for Ixodes scapularis Surveillance

Abstract

Tick dragging is an important tool used by public health for Ixodes scapularis surveillance to identify Lyme disease risk areas in Ontario, Canada. Concerns have been raised on the repeatability of tick dragging due to fluctuations that occur in the tick population in response to micro- and macroclimatic variations. Our objective was to assess the repeatability of tick dragging over a short timescale by examining three outcome measures: presence/absence of ticks, tick abundance, and likelihood of tick establishment based on an indicator developed by Clow et al. ( 2018 ). We conducted tick dragging twice per site within a 1-month period at a total of 15 sites in eastern and southern Ontario. Ixodes scapularis were detected at 11 sites. The outcome of presence/absence was consistent at 13 of 15 sites. Abundance was highly variable, changing between each visit at sites where ticks were detected. The likelihood level was consistent at 13 of 15 sites. Based on the kappa statistic, there was substantial agreement between measurements for the presence/absence and the likelihood levels. Our results indicate that both presence/absence and likelihood levels provide more consistent outcomes for tick dragging than tick abundance alone; however, applying the dragging data to the likelihood indicator provides additional information about the potential risk associated with I. scapularis establishment in the area.

Leveraging the Expertise of the New Jersey Mosquito Control Community to Jump Start Standardized Tick Surveillance

“…Lack of confidence in the results obtained may also help explain why individuals who collected fewer ticks than expected were less likely to collect after the Tick Blitz, although an alternative explanation is that they simply felt there were not many ticks in their county and did not see a need for additional surveillance. In either case, a better understanding of variability in tick collection and the drawbacks of current surveillance is needed [70,71].…”