IRM for Vector Control Insecticide Resistance Action Committee www.irac-online.org

Importance of IRM in Vectors Managing Resistance Mode of Action Classification

Insecticide resistance in public As with agricultural practices, the Biochemical mode of action of chemical classes of WHO- health vectors can profoundly affect best option currently is the rotation recommended insecticides for the control of mosquito public health through the possible of different modes of action rather larvae and adults, and their IRAC classification group re-emergence of vector borne than alternating members of one (IRAC) 1 diseases. Surveillance wherever chemical class or different Life stage Target site (mode of action) Chemical class IRAC Examples possible is essential to proactively chemical classes addressing the same target site. The Adults Acetylcholinesterase Organophosphate 1A Fenitrothion, malathion, react once a change in susceptibility of a public health presence of kdr resistance renders DDT and pyrethroids pirimiphos-methyl pest to an insecticide is observed. To this end the World less effective, whereas carbamates and organophosphates Carbamate 1B Bendiocarb, propoxur Voltage-gated sodium channel Pyrethroid 3 α-Cypermethrin, bifenthrin, Health Organization has published methods for the can still be used. If MACE (modified acetylcholinesterase) surveillance of resistance development to insecticides, e.g. deltamethrin, ethofenprox, as a mechanism is not present, rotational use of λ-cyhalothrin, permethrin by simple, rapid diagnostic dose bioassays for mosquitoes. organophosphates and carbamates can be considered DDT 3 DDT where product labelling and local regulations permit. In Larvae Acetylcholinesterase Organophosphate 1A Fenthion, chlorpyriphos, addition, the use of larvicides in conjunction with pirimiphos-methyl, pyrethroids can support resistance management through temephos Mode of Action rotation of MoA across different life stages. Effective Chitin biosynthesis Benzoylureas 15 Diflubenzuron, triflumuron, long-term resistance management is necessary, but many novaluron An important aspect impacting resistance development in factors need to be considered (including regional Juvenile hormone (JH) mimic JH analogues 7A Methoprene insect species important to public health is the availability availability of insecticides) to successfully implement Pyriproxyfen 7C Pyriproxyfen Midgut-membrane disruption Microbials 11A1 Bacillus thuringiensis of only a limited number of classes of insecticides strategies in order to effectively control insect vectors. registered for vector control. Since the advent of synthetic 11A2 Bacillus sphaericus insecticides only four chemically different classes of insecticides are (or have been) used to treat adult 1. Including larvicidal and adulticidal insecticides. This mode-of- action classification is regularly edited and updated to include mosquitoes, i.e. organochlorines (nowadays mostly Mechanisms of Resistance new products. Please refer to: banned), organophosphates, carbamates and www.irac-online.org for the complete mode of action list. pyrethroids Major biochemical mechanisms conferring resistance to important classes of insecticides in mosquitoes. A large spot indicates an important resistance mechanism; a smaller spot means this mechanism has been described IRAC IRM Monograph but is considered to be of lesser importance. A publication produced by IRAC: Biochemical mechanism of resistance Metabolic Target-site • Multi-authored

Esterases Monooxygenases GSH S-Transferases kdr MACE • 10 Chapters incl. figures & tables • 5,000 copies printed (Dec. 2006) Pyrethroids • Available free of charge DDT • Funded by the Bill & Melinda Gates Carbamates Foundation Organophosphates • Copies via the IRAC website

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