Major effect genes or loose confederations? The development of insecticide resistance in the malaria vector Anopheles gambiae

Abstract

Insecticide use in public health and agriculture presents a dramatic adaptive challenge to target and non-target insect populations. The rapid development of genetically modulated resistance to insecticides is postulated to develop in two distinct ways: By selection for single major effect genes or by selection for loose confederations in which several factors, not normally associated with each other, inadvertently combine their effects to produce resistance phenotypes. Insecticide resistance is a common occurrence and has been intensively studied in the major malaria vector Anopheles gambiae, providing a useful model for examining how insecticide resistance develops and what pleiotropic effects are likely to emerge as a consequence of resistance. As malaria vector control becomes increasingly reliant on successfully managing insecticide resistance, the characterisation of resistance mechanisms and their pleiotropic effects becomes increasingly important.

Insecticide resistance, associated mechanisms and fitness aspects in two Brazilian Stegomyia aegypti (= Aedes aegypti) populations

“…With respect to pyrethroids, previous evaluations are available only for Aracaju. Soon after the introduction of pyrethroids in the control of S. aegypti in Brazil, qualitative analysis detected incipient alterations in susceptibility in this locality (da-Cunha et al, 2005). The present study has confirmed that Aracaju resistance to deltamethrin is already installed (RR 95 = 17.8).…”

“…This may be partly attributable to the domestic use of pyrethroid products, which are directly available to the population, as some authors have suggested (Maciel-de-Freitas et al, 2014). In addition, this rapid dissemination of pyrethroid resistance, detected in some field samples from 2001 (da-Cunha et al, 2005), may also be the consequence of a cross-resistance mechanism.…”

“…This process, in general, has a significant impact on insect viability (Berticat et al ., ; Rivero et al ., ; Diniz et al ., ). However, it is possible that the Crato population may have suffered compensatory mutations that ameliorated its fitness, as has been seen in other vectors and in drug‐resistant microorganisms (Brooke & Koekemoer, ).…”

“…With respect to adult mosquitoes, the domestic use of pyrethroid insecticides has probably contributed to the selection of resistant populations (da-Cunha et al, 2005;Montella et al, 2007;Linss et al, 2014). This uncontrolled use of pyrethroids available on the retail market increases during periods of epidemics and, although difficult to quantify, is presumed to induce resistance even when no pyrethroid applications are made by public health personnel (Maciel-de-Freitas et al, 2014).…”

DDT and pyrethroid resistance in Anopheles arabiensis from South Africa

“…Cytochrome oxidases (P450s), glutathione S-transferases (GSTs) and esterases are generally associated with enzymatic detoxification of insecticides, while mutations in the voltage-gated sodium channel (commonly referred to as knockdown resistance or “ kdr ”) effectively decrease target site sensitivity [4,5]. The occurrence of kdr mutations is easily detected through the use of a polymerase chain reaction (PCR) assay [5] but this mechanism is not clearly correlated with all instances of pyrethroid resistance, especially deltamethrin resistance [6]. Identifying metabolic based resistance is more challenging and costly, especially when using microarrays [7].…”