Monitoring Drug Sensitivity In Cattle Ticks

Use of acaricides is one of the key strategies to protect cattle herds on pasture against tick infestation with Rhipicephalus (Boophilus) microplus. Unfortunately, the constant exposure to drugs has led to a selection of resistance to most of the chemical classes. Under these conditions it is even more important to know which drugs (or acaricide classes) can still be used and to what extent they provide protection. While testing drugs in vivo is costly and does not provide information on susceptibility to alternative acaricides, the in vitro tests seem more appropriate: they are less expensive and provide more data on the level of resistance against various chemical classes. Hence, resistance can be confirmed and differentiated using in vitro bioassays, as well as through the use of biochemical or molecular tests to detect metabolic- and target-site-based resistance, respectively. This chapter describes the currently available assays for determining the drug sensitivity status of tick populations, and discusses the advantages and limitations of the various assays.