Drug Resistance in Arthropod Parasites

Abstract

Despite considerable progress during the past 20 years in the development of nonchemical means of ectoparasite management, chemotherapy remains the basis, or an important adjunct, of many control programs designed to maximize production. There can be no argument that the greatest threat to stable chemical control and progress in the management of ectoparasites, and the diseases of which they are vectors, is the continued, and probably inevitable, emergence of pesticide resistance. The threat comes not only from the crises that are likely to arise in vector and disease outbreaks with the emergence of new resistant strains of parasites, but more importantly every new strain makes the task of finding replacement compounds more difficult. This difficulty arises partially because of ever-increasing costs associated with the development, and registration, of new materials. Of greater concern is the accumulation of resistance alleles in the population, which, with their associated biochemical and physiological defense mechanisms, constitute a formidable array of obstacles for any new chemical class to overcome. The latter problem can pose a difficult and expensive barrier to discovery and development, particularly as experience has shown that resistance mechanisms, selected by contemporary and previously used chemicals, often operate against structurally unrelated compounds. Thus, predictions on the expected life of even new chemical classes are difficult to make.