Mechanisms of resistance to chemicals in arthropod parasites of veterinary importance.

This review evaluates the significance, for ectoparasites, of the four resistance mechanisms that have emerged in arthropods as defence against chemicals used for their control. In particular the contrast of the relative importance of each mechanism in each of the major ectoparasitic pests of economic importance (sheep blowflies, mosquitoes and ticks) is discussed. Use is made of the experience gained in attempting to overcome these mechanisms to assess the consequences of resistance, and the chances for prolonging the useful life of pesticides, by suppressing the mechanisms, as an alternative to seeking replacement compounds.