Borgmann-Winter and Allen
How the distance between drag-cloth checks affects the estimate of adult and nymphal Ixodes scapularis (Acari: Ixodidae) density
J. Med. Entomol., 2019, in press, doi: 10.1093/jme/tjz179
While numerous methods have been developed for collecting ticks, the most commonly used method is dragging (flagging) a cloth along the ground and to check at regular intervals to count (and/or pick up) the ticks attached to the cloth. One major drawback of this method is that ticks may drop off the cloth while sampling and longer distance intervals could result in more ticks dropping off the drag cloth between the checks resulting in a lower estimate of questing tick density. The authors observed that with increasing distance between checks while dragging Ixodes scapularis ticks, the estimated tick density decreased significantly for nymphs and adult ticks. The drop-off rate may be influenced by the drag-cloth material used, the temperature and the ground structure/vegetation type. Checking every 10 m will capture 79% of nymphs attached to the cloth, checking every 20 m will capture 65% of nymphs, and checking every 30 m will capture 54% of nymphs. Different cloth check frequencies may thus have an impact on the nymphal density estimated by dragging/flagging. The effect seen here is not only true for I. scapularis but has also been observed earlier for I. pacificus and Dermacentor variabilis (Li and Dunley, Exp. Appl. Acarol. 1998, 22:233-248) and may be considered for every questing tick species to be dragged/flagged.