title: Ticks in the wrong boxes: assessing error in blanket-drag studies due to occasional sampling.
abstract: BACKGROUND
  The risk posed by ticks as vectors of disease is typically assessed by blanket-drag sampling of host-seeking individuals. Comparisons of peak abundance between plots - either in order to establish their relative risk or to identify environmental correlates - are often carried out by sampling on one or two occasions during the period of assumed peak tick activity.
  
  
  METHODS
  This paper simulates this practice by 're-sampling' from model datasets derived from an empirical field study. Re-sample dates for each plot are guided by either the previous year's peak at the plot, or the previous year's peak at a similar, nearby plot. Results from single, double and three-weekly sampling regimes are compared.
  
  
  RESULTS
  Sampling on single dates within a two-month window of assumed peak activity has the potential to introduce profound errors; sampling on two dates (double sampling) offers greater precision, but three-weekly sampling is the least biased.
  
  
  CONCLUSIONS
  The common practice of sampling for the abundance of host-seeking ticks on single dates in each plot-year should be strenuously avoided; it is recommended that field acarologists employ regular sampling throughout the year at intervals no greater than three weeks, for a variety of epidemiological studies.
authors: School of Biological and Environmental Sciences, University of Stirling, Cottrell Building, FK9 4LA, Stirling, UK. andrew.dobson@stir.ac.uk.
authors: Andrew D M
authors: AD
authors: Dobson
mesh_terms: D000818:Animals; D004772:Entomology / Q000379:methods*; D013987:Ticks / Q000145:classification* / Q000254:growth & development*; D013997:Time Factors