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

Area of Science:

• Vector-borne disease ecology
• Epidemiological surveillance methods
• Entomology

Background:

• Tick dragging is crucial for Ixodes scapularis surveillance in Ontario, Canada, to map Lyme disease risk.
• Concerns exist regarding tick dragging repeatability due to climate-driven tick population fluctuations.

Purpose of the Study:

• To evaluate the short-term repeatability of tick dragging for Ixodes scapularis surveillance.
• To compare the consistency of three outcome measures: presence/absence, abundance, and establishment likelihood.

Main Methods:

• Tick dragging was performed twice within one month at 15 sites in eastern and southern Ontario.
• Outcome measures included tick presence/absence, abundance, and an establishment likelihood indicator.
• Kappa statistics were used to assess agreement between repeated measurements.

Main Results:

• Ixodes scapularis was detected at 11 of 15 sites.
• Presence/absence and likelihood levels showed consistency at 13 of 15 sites.
• Tick abundance varied significantly between sampling visits, while likelihood levels demonstrated substantial agreement.

Conclusions:

• Presence/absence and likelihood levels are more repeatable measures for tick dragging than abundance alone.
• The likelihood indicator, combined with dragging data, offers valuable insights into potential Ixodes scapularis establishment risk.