Data acquisition and sampling period

The minimum number of tick submissions (N) required to compare the sensitivity and specificity of ‘eTick’ to the conventional system was estimated at 245 using the method of Greiner and Gardner (2000) based on the standard formula for estimating sensitivity and specificity

where Z_1−α/2 (the number of standard deviations from the mean of a normal distribution required to contain 0·975 of the area) = 1·96, α = 0·05, θ was the assumed a priori estimate of sensitivity or specificity (set at 0·8), and e was the error margin on the estimate (set at ±0·05) [using recommended values in Greiner and Gardner (2000)].

A pilot test conducted in fall 2014 with ten voluntary veterinary clinics in Quebec to ensure that the web platform was simple and flexible enough yielded ten high-quality submitted digital images. In 2015, to reach our target of 245 submissions (but anticipating a participation rate of <40% based on the 2014 pilot), 122 clinics who had submitted at least five ticks to the passive surveillance programme the previous year were contacted by telephone and e-mail to request their voluntary participation to the project.

Adult I. scapularis are active mostly in spring and autumn but other species are mostly active in summer (Ogden et al. 2010; Bouchard et al. 2013). Therefore, the 2015 sampling season extended from April to December to ensure the collection of multiple tick species.