Bottle-Acaricide-Impregnation-Test (BAIT): an alternative novel bioassay for diagnosis of acaricide tick-tolerance and/or resitance

Background: Ticks are blood-feeding ectoparasites which transmit pathogens ranging from protozoa, viruses, bacteria to both humans and animals. For decades, acaricides have significantly contributed to reduction of the tick-population, and tick-borne diseases. However, there is an increase in acaricide tick-resistance globally. Since the 1960s, diagnosis of acaricide-resistant ticks relies mainly on two methods: the Larval Packet Test (LPT) and the Adult Immersion Test (AIT). The limitations of these methods are for instance, (1) each assay is restricted to one stage of tick-development. (2) the assays require special additional reagents and materials therefore unaffordable in resource constrained regions. Objective: To address these gaps, we have developed an alternative novel method named: the Bottle-Acaricide-Impregnation-Test (BAIT) and assessed its efficacy. Methodology: We examined the potential of BAIT to detect acaricide resistant and/or tolerant ticks. Three acaricides: DuoDip (Organophosphate), Norotraz (Amidine) and SyperTix (Synthetic pyrethroid) were independently tested against unfed and fed Rhipicephalus appendiculatus colony ticks at different stages of development (larvae, nymphs and adults). The test acaricides were applied separately at single (1x) and double (2x) working concentration and the efficacy of the BAIT assessed in comparison with the AIT, LPT and Nymph Immersion Test (NIT). Results: Our data reveals that: (1) the BAIT assay is as efficient as the AIT, LPT, and NIT, and (2) the efficiency of the tests does not vary with acaricide class or concentration (3). Conclusion: The BAIT method is universal to all tick-developmental stages, simpler, cheaper and could be applicable both under field and laboratory conditions.