Validating a common tick survey method: cloth-dragging and line transects

Abstract

Cloth-dragging is the most widely-used method for collecting and counting ticks, but there are few studies of its reliability. By using cloth-dragging, we applied a replicated line transects survey method, in two areas in Sweden with different Ixodes ricinus tick-densities (low at Grimsö and high at Bogesund) to evaluate developmental stage specific repeatability, agreement and precision in estimates of tick abundance. ‘Repeatability’ was expressed as the Intraclass Correlation Coefficient (ICC), ‘agreement’ with the Total Deviation Index (TDI) and ‘precision’ by the coefficient of variation (CV) for a given dragging distance. Repeatability (ICC) and agreement (TDI) were higher for the most abundant instar (nymphs) and in the area of higher abundance. At Bogesund tick counts were higher than at Grimsö and so also repeatability, with fair to substantial ICC estimates between 0.22 and 0.75, and TDI ranged between 1 and 44.5 counts of difference (thus high to moderate agreement). At Grimsö, ICC was poor to moderate and ranged between 0 and 0.59, whereas TDI remained low with estimates lower or equal to 1 count (thus high agreement). Despite a 100-fold lower abundance at Grimsö, the same level of precision for nymphs could be achieved with a 70% increase of dragging effort. We conclude that the cloth-dragging technique is useful for surveying ticks’ and primarily to estimate abundance of the nymphal stage, whereas it rarely will be recommended for larvae and adults.

Exploring the Individual Bacterial Microbiota of Questing Ixodes ricinus Nymphs

“…The number of adult ticks ( n = 29) represented 9.2% of our overall collection which was much lower than the number of nymphs collected ( n = 315). This is in line with other studies that have employed a dragging protocol to collect questing ticks [ 78 , 79 , 80 ]. We chose to study I. ricinus nymphs only for three main reasons.…”

Longer study length, standardized sampling techniques, and broader geographic scope leads to higher likelihood of detecting stable abundance patterns in long term black-legged tick studies

“…However, other research has found that data produced using different tick sampling methods is similar ( Rulison et al, 2013 ). Yet even more recent research attempting to validate dragging with other tick species in Sweden concluded that dragging was not recommended for tick adults or larvae, due to low repeatability and agreement ( Kjellander et al, 2021 ). This may be due to the lack of standardization within dragging cloths or other within-method variability between surveys ( Newman et al, 2019 ).…”

Meteorological and climatic variables predict the phenology of Ixodes ricinus nymphs activity in France, accounting for habitat heterogeneity

“…The present study attempted to explore the baseline abundance, seasonal, and interannual variations of I. ricinus nymph activity by expanding the observation across a wide range of geographical/climatic areas over a long period, involving a total of 11 sampling sites from 7 tick observatories in France over 8 years. With the repeated removal sampling design, we controlled the uncertainty on the proxy measure of tick abundance (nymph counts per 100 m 2 ) that arises from the variability of sampling rate across different sites and times 24,49 . Furthermore, all transects were covered with low vegetations, which were shown to maximize sampling rates compared to other types of vegetative oors 24 , resulting in higher accuracy in estimating the proxy of tick abundance.…”