Testing the efficiency of capture methods for questing Hyalomma lusitanicum ticks (vector of Crimean-Congo hemorrhagic fever virus)

Abstract

Abstract Background Available methods to census exophilic tick populations have limitations in estimating true population size due to their inability to capture a high proportion of the actual tick population. We currently ignore the efficacy of these methods to capture questing Hyalomma spp. ticks, vectors of the Crimean-Congo hemorrhagic fever virus. To address the need to accurately estimate questing densities of Hyalomma spp. we designed a field experiment to test the efficacy of blanket dragging, blanket flagging, CO2-baited traps, and and ad hoc designed method, absolute surface counts, in capturing adult Hyalomma lusitanicum ticks. Methods The experiment was designed in two stages to estimate the point (one-day sampling) and cumulative (three-day serial sampling) efficacy of the methods under varying sampling effort and habitat. Tick survival, host interference, and weather effects on efficacy were controlled for in multiple regression models. Results There was high variability in method efficacy for capturing ticks, which was also modulated by effort and habitat. The most effective method was absolute surface counts for both point estimates (39%) and cumulative efficacy (83%). CO2-baited traps reached a maximum efficacy of 37%, while blanket dragging and blanket flagging captured around 8% of the marked ticks. Conclusions Our results reveal the strengths and weaknesses of the different tick capture methods applied to study the demography of H. lusitanicum, and lay the groundwork for more accurate inferences about the true size of exophilic tick populations.