Introduction
Ticks most notably Rhipicephalus (Boophilus) microplus are becoming increasingly resistant to acaricides .This resistance is often broken down into the 3 main mechanisms of detoxification involving 3 groups of enzymes; Cytochrome P450s (CYPs), Glutathione-S-transferases (GST) or Esterases (EST or carboxylesterases) (Foil et al., 2004)
Material and Methods
Acaricide resistance research to date, has focused on identifying which acaricides are becoming redundant in terms of effectiveness to kill the arthropod. Often, this research uses mortality based experimental procedures (Li et al., 2003; Miller et al., 2005), and investigations into the molecular/enzymatic basis of resistance have focused on GSTs and ESTs rather than CYPs. Another method used in our laboratory investigating the role of CYPs in resistance is employing tick cell cultures as a model system developed in partnership with the Roslin Institute (Bell-Sakyi et al., 2007). This system provides an ideal way to monitor CYP expression before, during and after various treatments such as acaricides. In Anopheles gambiae, expression levels of CYPs, GSTs and ESTs were monitored using a microarray following infection of the mosquito by Plasmodium (Felix et al., 2010). A similar micro array approach could be employed with ticks and mites as more data becomes available.
Results
Our group is monitoring the expression levels of different CYPs in tick cell lines as well as looking to identify novel CYPs and work on phylogenetic links for those genes between different arthropod groups. We are also investigating polymorphisms between different tick cell lines and different arthropod species.
Discussion and Conclusions
Among the arthropods, research strongly suggests that the CYP6 (Hemingway et al., 2004) and CYP9families are most highly associated with xenobiotic resistance and a lot of research has been carried out looking at these CYP families in various insect species. In mosquito species some resistance to pesticides is due to their CYP enzymes evolving to detoxify these chemicals at increasing concentrations (Nikou et al., 2003
