Determination of optimum age of Rhipicephalus microplus tick larvae for monitoring esterase mediated resistance development

Acaricide resistance in ticks is one of the major problems hampering tick management. Currently, bioassays are used as gold standard tests to determine acaricide resistance. These tests are costly, time consuming and do not provide information on the reasons for resistance. In comparison, biochemical test like esterase assay is cheaper, robust, less time consuming and can analyse large number of samples at a time. Esterase plays crucial role in blood digestion, host attachment and detoxification of acaricides in ticks. However, the assay is not yet standardized in tick system. In the present study, reference characterized tick lines of Rhipicephalus microplus were used to determine the age at which most significant result can be obtained. It was concluded that 10–14 days old larvae are most appropriate for conducting the esterase assay. Peak esterase activity at this age also provides evidence for successful attachment of tick to hosts.