How the Distance Between Drag-Cloth Checks Affects the Estimate of Adult and Nymphal Ixodes scapularis (Acari: Ixodidae) Density

Abstract

Drag-cloth sampling is the most commonly used method to sample for ticks. A cloth is dragged along the ground and checked for ticks at regular intervals to count ticks before they drop off. The distance between drag-cloth checks differs between studies, which could result in lower density estimates for studies with greater distances between checks. Here, we measured this effect by 1) calculating the rate at which nymphal and adult Ixodes scapularis Say ticks drop off the cloth per meter dragged and 2) measuring tick density by drag-cloth sampling with three different drag-cloth check interval distances. We found a higher drop-off rate for adult ticks, 0.083/m, than nymphal ticks, 0.047/m. The estimated density of ticks decreased with increasing check interval distance. Our results not only highlight the importance of accounting for check interval distance when estimating tick density, but also provide the first estimate of nymphal I. scapularis drop-off rate.

Keywords: Ixodes scapularis; drag-cloth sampling; nymph; sampling bias.