International Journal of Pulmonology and Infectious Diseases

Objectives: The aim of the study was to know the status of insecticide resistance to mosquito in Ethiopia. As well as what questions were answered and for next what questions needed to be answered.

Results: Extreme resistance to DDT and pyrethroids was insidious across Ethiopia, related with historic use of DDT for indoor residual spray and concomitant increases in insecticide-treated net coverage over the last 17 years. Longitudinal resistance trends to malathion, bendiocarb, propoxur and pirimiphos-methyl corresponded to shifts in the national insecticide policy. DDT resistance was widely distributed in Ethiopia and DDT was replaced by deltamethrin. Moreover, in 2012 Ethiopia switched from deltamethrin to bendiocarb for indoor residual spray in response to the observed resistance. All the study that conducted in Ethiopia was only focused on mosquitoes that are vectors for malaria.

Key words: Mosquito; Insecticide resistance; Ethiopia;

Insect vectors accounts for almost 20 per cent of all infectious diseases affecting people in developing countries [1]. Significant vector borne diseases, such as malaria, typhus fever, yellow fever, and insect borne enteric infections, have been controlled effectively in certain parts of the world and nearly eradicated in others through the use of insecticides [2].There are four main classes of neurotoxic insecticides that are recommended or prequalified by WHO for indoor residual spray (IRS) namely: carbamates, organochlorines, organophosphates and pyrethroids, But only pyrethroids are recommended for insecticide-treated nets (ITNs) due to their relatively low toxicity to humans, a rapid knockdown effect on mosquitoes, and low cost [3]. From the time when pyrethroids are introduced for ITN impregnation in the 1980s, no new adulticide has been approved for ITN treatment [4].

The mechanisms of insecticide resistance vary widely, as target sites and mechanisms of degradation can differ among insecticides. These classes of insecticides mainly target receptors in the mosquito’s nervous system or inhibit enzymes involved in transmitting nerve impulses, causing paralysis and insect death. Some target sites are shared by different classes of insecticides. DDT and pyrethroid insecticides act through the receptor for the voltage-dependent sodium channel (CNaVdp), organophosphates and carbamates target acetylcholin esterase (AChE), and cyclodiene insecticides target the gene coding for the gammaaminobutyric acid (GABA) receptor [5]. Resistant strains have mutations in target sites or genes that code for enzymes that impact the effectiveness of a specific insecticide.

Even though insecticides are quite effective when used according to technical indications, some of the factors that affect insecticides effectiveness are the use of poor quality insecticides of or adulterated processes of resistance in insects, failures in the processes of preparation and application, among others [6].The development of resistance to insecticides by many insect vectors which transmit different diseases, threatens the continuation and extension of worldwide progress in the control of vector borne diseases. For this reason, insect resistance is internationally recognized by leading health authorities as the most important problem facing organized vector borne disease control programs [7]. Different insect vectors have developed resistance due to mismanagement of the insecticides used [8]. Resistance can be understood as the inability of an insecticide used according to the technical indications to achieve an adequate control of a pest or group of pests, due to genetic modifications in the target species, which make them less sensitive to the applied product [9].

About 325 insecticides already have technical reports of resistance by one or more species [10]. Different levels of resistance have been found in the different classes of insecticides. DDT, organochlorines, carbamates, organophosphates, pyrethroids and pyrethrins are the chemical groups that present a higher level of resistance, mainly due to their diversity of chemical compounds and for the long time of use in the market; however, in other insecticides considered as new generation, resistance reports also have been found [11].

The mechanisms of resistance can be divided into two main groups: physiological and behavioral. Physiologically, the resistance can be presented by changes in the site of action of the insecticide, due to specific mutations in the receptors, which limits the ability of the toxic to bind to the receptor molecule or affects its function after the union. The second mechanism of resistance is biotransformation, which involves the metabolic destruction of the insecticide within the organism, by means of biochemical processes such as hydrolysis, oxidation or conjugation, wherever some enzymes play a preponderant role such as esterases, glutathione-S-transferases and cytochrome P450 monoxygenases [12,13]. Resistance can also occur because of a reduction in the rate of cuticular penetration, which prevents the insecticide from reaching its lethal concentration, and on the contrary allows the body to metabolize and eliminate the drug with minimal or absent toxic effects. Finally, physiological resistance can occur due to the binding of the insecticide with non-objective macromolecules, so it does not exert any toxic action [13]. On the other hand, behavioral resistance should be understood as the heritable capacity of an insect to avoid contact with an insecticide, which results in a measurable decrease in susceptibility to a toxic [14].

The pyrethroid chemical family is described as having low tox¬icity on humans. Insecticidal molecules belonging to these four families target different ion channels or en¬zymes to interrupt the proper functioning of the insect nervous system [15].Mutations in the amino-acid sequence of binding site of the insecticide target as well as metabolic changes, lead to frequent resistance in mos¬quito populations [16]. After decades of insecticide pressure, mosquito populations have become resistant to multiple chemical insecticide families, compromising the effectiveness of chemical-based control [17,18].

Unluckily, in the last decade pyrethroid resistance has become widespread in Anopheles genera in Sub-Saharan Africa [18]. This was mainly driven by the high selective pressure stemming from the huge use of pyrethroids in agriculture and the scaling-up of pyrethroid ITNs and IRS for malaria control [19-21]. Although the epidemiological impact of resistance mechanisms on vector control remains controversial, numerous reports of pyrethroid resistance have discovered reduced vector mortality and a consequent drastic loss of personal protection conferred by pyrethroid-treated nets to humans [22]. Sixty one countries reported mosquito resistance to at least one insecticide used in nets and IRS [23]. This situation represents a serious threat to the efficacy of malaria control tools. The WHO recommends the use of insecticide combinations with different modes of action for LLIN impregnation in order to manage pyrethroid resistance in malaria vectors; the underlying hypothesis is that insects that can survive contact with one component of the mixture would be killed by the second insecticide [24,25].

Chlorfenapyr has been shown to have the potential to provide improved control of pyrethroid-resistant An. gambiae both in laboratory and in controlled conditions against natural freeflying resistant malaria vectors [26]. A mixture of chlorfenapyr and alpha-cypermethrin on bed nets has been shown to provide excito-repellency and strong insecticidal activity against pyrethroid resistant mosquitoes [27,28]. Recently, BASF® developed a long-lasting insecticidal mixture net, called Interceptor G2, that is made of polyester fibers and treated with a mixture of alphacypermethrin/chlorfenapyr. The World Health Organization Pesticide Evaluation Scheme (WHOPES) reviews and makes recommendations on new pesticide technologies for public health programs, such as LLINs [29].

There are local evidences showing the widespread of insecticide resistance to various chemicals used for IRS. Intense resistance to DDT and pyrethroids was persistent across Ethiopia, consistent with historic use of DDT for IRS and concomitant increases in insecticide-treated net coverage over the last 17 years. Longitudinal resistance trends to malathion, bendiocarb, propoxur and pirimiphos-methyl corresponded to shifts in the national insecticide policy. By 2016, resistance to propoxur and pirimiphos-methyl insecticides had emerged, with the potential to jeopardize future long term effectiveness of vector control activities in these areas. Between 2015 and 2016, the West African (L1014F) kdrallele was detected in 74.1% (n = 686/926) of specimens, with frequencies ranging from 31 to 100% and 33 to 100%in survivors from DDT and deltamethrin bioassays, respectively. Restoration of mosquito susceptibility, following pre-exposure to PBO, along with a lack of association between kdrallele frequency and An. Arabiensis mortality rate, both indicate metabolic and target-site mutation mechanisms are contributing to insecticide resistance [30]. DDT resistance was widely distributed in the country and DDT was replaced by deltamethrin. Moreover, in 2012 Ethiopia switched from deltamethrin to bendiocarb for IRS in response to the observed resistance. Populations of An. arabiensis were resistant to DDT and deltamethrin but were susceptible to fenitrothion in all the study sites. Reduced susceptibility to malathion, pirimiphosmethyl, propoxur and bendiocarb was observed in some of the study sites. Knockdown resistance (kdr L1014F) was detected in all mosquito populations with allele frequency ranging from 42 to 91%. Elevated levels of glutathione-S-transferases (GSTs) were detected in some of the mosquito populations [31].

In Ethiopia, target site resistance mechanism in populations of An. arabiensis was first reported from areas around the Gilgel Gibe hydro-electric dam, southwestern Ethiopia. The kdr allele frequency of the L1014F mutation in the Gilgel Gibe region was the highest ever reported in An. arabiensis [32]. Subsequent studies have also documented the same mutation in this species in other parts of the country [33–35].

Anopheles gambiae s.l. was sensitive to DDT only in 2 of 16 localities where susceptibility studies were carried out in northern Ethiopia; it was resistant in 11 sites and potentially resistant in three. To malathion, the test population was sensitive in four of the six study sites in southern Ethiopia and potentially resistant in the other two sites. In northern Ethiopia, the population was resistant in five localities and sensitive in three. Of the six localities in northern Ethiopia where permethrin was tested, populations were sensitive in three, resistant in one and potentially resistant in two. In southern Ethiopia, the populations were resistant in five of the six sites. Against deltamethrin, the population was sensitive in five of 13 localities, three in northern and two in southern Ethiopia. It was resistant only in two localities, one in northern and one in southern Ethiopia, and potentially resistant in five localities. In eastern Ethiopia at Sabure, the population was sensitive to all insecticides but DDT to which it was potentially resistant [36].

The mechanisms responsible for insecticide resistance are complex and include behavioral and/or physiological changes of mosquitoes leading to insecticide avoidance, altered penetration, sequestration, target site alteration or biodegradation. In mosquitoes, resistance is mainly associated with target site modification and metabolic resistance. Target site resistance involves mutations leading to well defined target site alteration and resistance to chemical insecticides [37]. Metabolic resistance, on the other hand, involves more subtle alterations in the expression of a complex array of enzymes and detoxification pathways, the mechanisms of which are far less well understood [38,39]. Metabolic resistance occurs through increased biodegradation of the insecticide, usually through overproduction of detoxification enzymes such as P450s, glutathione S-transferases (GSTs) and carboxy/cholinesterases (CCE) [39]. Of these, P450sare the primary enzyme family associated with resistance to most insecticides including pyrethroids, the most widely used class of insecticide for vector control. Elevated levels of P450s activity are frequently observed in pyrethroid-resistant malaria vectors in Africa [37,40-44]. Esterase hydrolysis of pyrethroids leading to detoxification is also believed to act as a cause of metabolic resistance in some instances, while GSTs are regularly found over expressed in pyrethroid-resistant strains [45,46]. However, the contribution these enzymes make towards pyrethroid resistance and their biochemical relationships with P450-mediated resistance is still unclear.

Several P450s in An. gambiae associated with pyrethroid resistance includes CYP6Z1, CYP6Z2, CYP6M2, CYP6P3 and CYP325A3 [44,47,48]. Of these, CYP6P3 and CYP6M2 have appeared most widely over-transcribed in resistant field populations [43,44].Importantly, they have been shown to metabolize permethrin and deltamethrin, thus operationally are considered key diagnostic markers of resistance [49,50]. Most recently, high levels of CYP6M2 gene expression have been found in a highly DDT-resistant population of An. gambiae from Ghana, using a novel whole genome microarray [51]. Likewise, CYP6Z1 has been found over expressed in both pyrethroid and DDT resistant strains and shown to metabolize DDT, placing it in the frontline of metabolic resistance markers for DDT [52].

Resistance mechanisms in An. funestus, the second major vector of malaria in Sub-Saharan Africa, the use of quantitative trait loci (QTL) has identified CYP6P9, CYP6P4, CYP6Z1, CYP6Z3 and CYP6M7 as being strongly associated with pyrethroid resistance [53,54]. CYP6Z1 and CYP6Z3 have already been linked with insecticide resistance in An. gambiae, while CYP6P9 and CYP6M7are orthologues of An. gambiae resistance markers, CYP6P3and CYP6M2, respectively. To date, increased levels of CYP6P9 have been most frequently observed in pyrethroidresistant laboratory and field populations from Mozambique, Uganda and Benin[40,41,53,55-58].

Pyrethroid resistance is now wide spread in Sub-Saharan Africa. Novel insecticides to manage pyrethroid resistance are critical to maintain the efficacy of malaria vector control. The pyrrole insecticide chlorfenapyr has been identified as a novel insecticide of interest to public health. In Ethiopia, we have found studies only related to insecticide resistance to malaria vector mosquito.

The limitation of this study is we reviewed only those which were accessed in online as open access.

Not applicable

Not applicable

Data is available in PDF and MS word

Not applicable

We want to acknowledge for the researchers who cited as a reference in this manuscript. Because we grasp information regarding mosquito insecticide resistance in our local.

The authors declare that they have no competing interests.

GT and GG wrote and edited the manuscript. All authors read and approved the final manuscript.

1. WHO. 2004 WHO Regional Office for the Eastern Mediterranean, integrated vector management: strategic framework for the Eastern Mediterranean Region 2004–2010. Geneva, Switzerland: World Health Organization.
2. Simmons SW and Grant JS. Current status of insecticide resistance. In Proceedings, 3d Conference of Industrial Council for Tropical Health, Cambridge, Mass. Harvard School of Public Health. 1957.
3. WHO. 2011. World Malaria Report 2011. World Health. Organisation: Geneva
4. Nauen R. Insecticide resistance in disease vectors of public health importance. Pest Management Science. 2007;63(7):628–633.
5. Karunamoorthi K and  Sabesan S. Insecticide Resistance in Insect Vectors of Disease with Special Reference to Mosquitoes: A Potential Threat to Global Public Health. Health Scope. 2013;2:4-18.
6. Djogbénou L, Chandre F, Berthomieu A, Dabiré R and KoffiA, Alout H. et al. Evidence of introgression of the ace-1R mutation and of the ace-1 duplication in West African Anopheles gambiaes.s.PLoS One. 2008;3(5):e2172.
7. Hess AC. The significance of insecticide resistance in vector control programs. Am. J. Trop. Med. &Hyg. 1953;1:371-388.
8. Kikuchi Y, Hayatsu M, Hosokawa T, Nagayama A, Tago K and Fukatsu T . Symbiont-mediated insecticide resistance. Proc Natl Acad Sci USA. 2012;109(22):8618-8622.  Doi: 10.1073/pnas.1200231109.
9. Nauen R, Elbert E, Mccaffery A, Slater R and Sparks TC. IRAC: Insecticide Resistance, and Mode of Action Classification of Insecticides. In: Kramer W, SchirmerU, Jeschke P, Witschel M (Eds) Modern Crop Protection Compounds, 2nd Edition. 2012; 935-955.
10. Sparks TC and Nauen R. IRAC: Mode of action classification and insecticide resistance management. Pestic Biochem Physiol. 2015;121:122-128.  Doi: 10.1016/j.pestbp.2014.11.014.
11. Whalon ME, Mota-Sanchez D and Hollingworth RM. Analysis of Global Pesticide Resistance in Arthropods. In: Whalon ME, Mota-Sanchez D, Hollingworth RM (Eds) Global Pesticide Resistance in Anthropods. CAB International, UK. 2008;5-31.
12. Hollingworth R M and Dong K. The Biochemical and Molecular Genetic Basis of Resistance to Pesticides in Arthropods. In: Whalon ME, Mota-Sanchez D, Hollingworth RM (Eds) Global Pesticide Resistance in Anthropods, Chapter 3, CAB International, UK. 2008;40-89.
13. Montella IR, Schama R and Valle D.  The classification of esterases: an important gene family involved in insecticide resistance--a review. MemInstOswaldo Cruz. 2012;107(4):437-449.
14. Zalucki MP and Furlong MJ. Behavior as a mechanism of insecticide resistance: evaluation of the evidence. CurrOpin Insect Sci. 2017;21:19-25.  Doi: 10.1016/j.cois.2017.05.006.
15. Liu N. Insecticide resistance in mosquitoes: impact, mechanisms, and research directions. Annu Rev Entomol. 2015;60: 537-559. Doi: 10.1146/annurev-ento-010814-020828.
16. Ranson H, Burhani J, Lumjuan N and Black IV WC. Insecticide resis­tance in dengue vectors. TropIKA.net. 2010;1(1):1-17.
17. Ranson H, Lissenden N. Insecticide resistance in African Anopheles mosquitoes: a worsening situation that needs urgent action to maintain malaria control. Trends Parasitol. 2016;32(3):187-196. Doi: 10.1016/j.pt.2015.11.010.
18. Ranson H, N’Guessan R, Lines J, Moiroux N, Nkuni Z and Corbel V. Pyrethroid resistance in African anopheline mosquitoes: what are the implications for malaria control? Trends in Parasitology. 2011;27(2):91–98. Doi: 10.1016/j.pt.2010.08.004.
19. Dabiré RK, Namountougou M, Diabaté A, Soma DD, Bado J and Toé HK. et al. Distribution and frequency of kdr mutations within Anopheles gambiaes.l. populations and  first report of the Ace.1G119S mutation in Anopheles arabiensis from Burkina Faso (West Africa). PLoS One. 2014;10(11):e0141645.
20. Luc DS, Benoit A, Laurette D and Michel M. Indirect evidence that agricultural pesticides select for insecticide resistance in the malaria vector Anopheles gambiae. Journal of Vector Ecology. 2016;41(1):34–40. Doi: 10.1111/jvec.12191.
21. Sharp BL, Ridl FC, Govender D, Kuklinski J and Kleinschmidt I. Malaria vector control by indoor residual insecticide spraying on the tropical island of Bioko, Equatorial Guinea. Malaria Journal. 2007;6:52. Doi:10.1186/1475-2875-6-52.
22. Asidi A, N’Guessan R, Akogbeto M, Curtis C and Rowl M. Loss of household protection from use of insecticide treated nets against pyrethroid-resistant mosquitoes, Benin. Emerging Infectious Diseases. 2012;18:1101–1106. Doi: 10.3201/eid1807.120218.
23. WHO. 2017. World malaria report 2017. World Health. organization: Geneva.
24. Pennetier C, Bouraima A, Chandre F, Piameu M, Etang J and Rossignol M. et al. Efficacy of Olyset_ Plus, a new long-lastinginsecticidal net incorporating permethrin and piperonilbutoxide against multi-resistant malaria vectors. PLoS One. 2013;8:e75134.
25. WHO. 2012. Global plan for insecticide resistance management in malaria vectors. World Health Organization: Geneva.
26. Oxborough RM, N’Guessan R, Jones R, Kitau J, Ngufor C and  Malone D. et al. Rowland MW. The activity of the pyrrole insecticide chlorfenapyr in mosquito bioassay: towards a more rational testing and screening of non-neurotoxic insecticides for malaria vector control. Malaria Journal. 2015;14:124.  Doi: 10.1186/s12936-015-0639-x.
27. N’Guessan R, Ngufor C, Kudom AA, Boko P, Odjo A and Malone D. et al. Mosquito nets treated with a mixture of chlorfenapyr and alphacypermethrin control pyrethroidresistantAnophelesgambiae and Culexquinquefasciatus mosquitoes in West Africa. PLoS One. 2014;9(2):e87710.  
28. Oxborough RM, Kitau J, Matowo J, Feston E, Mndeme R and Mosha FW. et al. ITN Mixtures of chlorfenapyr (pyrrole) and alphacypermethrin (pyrethroid) for control of pyrethroid resistant Anopheles arabiensis and Culexquinquefasciatus. PLoS One. 2013;8(2):e55781.32.
29. N’Guessan R, Odjo A, Ngufor C, Malone D, Rowland M. A chlorfenapyr mixture net interceptor_ g2 shows high efficacy and wash durability against resistant mosquitoes in WestAfrica. PLoS One. 2016;11(11):e0165925.
30. Messenger, Shililu, Irish, Anshebo, Tesfaye and Ebiyoetal. et al. Insecticide resistance in Anophelesarabiensisfrom Ethiopia (2012–2016): anationwide study for insecticide resistance monitoring Malar J.  2017;16:469.Doi: 10.1186/s12936-017-2115-2.
31. Alemayehu, Asale, Eba, Getahun, Tushune and Bryon. et al .Mapping insecticide resistance and characterization of resistance mechanisms in Anopheles arabiensis (Diptera: Culicidae) in Ethiopia.Parasit Vectors. 2017;10(1):407. Doi: 10.1186/s13071-017-2342-y.
32. Yewhalaw D, Van Bortel W, Denis L, Coosemans M, Duchateau L and Speybroeck N. First evidence of high knockdown resistance frequency in Anopheles arabiensis (Diptera: Culicidae) from Ethiopia. Am J Trop Med Hyg. 2010;83(1):122–125.
33. Doi: 10.4269/ajtmh.2010.09-0738.
34. Asale A, Getachew Y, Hailesilassie W, Speybroeck N, Duchateau L, Yewhalaw D. Evaluation of the efficacy of DDT indoor residual spraying and longlasting insecticidal nets against insecticide resistant populations ofAnophelesarabiensis Patton (Diptera: Culicidae) from Ethiopia using experimental huts. Parasit Vectors. 2014;7:131. Doi: 10.1186/1756-3305-7-131.
35. Meshesha B, Muntaser I, Koekemoer LL, Brooke BD, Engers H and Aseffa A, et al. Insecticide resistance in Anopheles arabiensis (Diptera: Culicidae) from villages in central, northern and south west Ethiopia and detection of kdr mutation. Parasit Vectors. 2010;3:40.
36. Fettene M, Olana D, Christian RN, Koekemoer LL and Coetzee M. Insecticide resistance in Anopheles arabiensis from Ethiopia. AfrEntomol. 2013;21(1):89–94.
37. Abate and  Hadis. Susceptibility of Anopheles gambiaes.l. to DDT, malathion,permethrin and deltamethrin in Ethiopia. Trop Med and International Heal. 2011;16(4):486–491. Doi: 10.1111/j.1365-3156.2011.02728.x.
38. Donnelly MJ, Corbel V, Weetman D, Wilding CS, Williamson MS and Black IV WC. Does kdr genotype predict insecticide-resistance phenotype in mosquitoes? Trends Parasitol. 2009;25(5):213–219. Doi:10.1016/j.pt.2009.02.007.
39. Feyereisen R. 2005 Insect P450. In Comprehensive molecule insect science (eds LI Gilbert, K Latrou, SSGill). Oxford, UK: Elsevier.
40. Hemingway J and Ranson H. Insecticide resistance in insect vectors of human disease. Annu. Rev.Entomol. 2000;45:371–391. Doi:10.1146/annurev.ento.45.1.371.
41. Amenya DA, Naguran R, Lo TC, Ranson H, Spillings BL and Wood OR. et al. Over expression of a cytochrome P450 (CYP6P9) in a major African malaria vector, Anopheles funestus, resistant to pyrethroids. Insect Mol. Biol. 2008;17(1):19–25. Doi:10.1111/j.1365-2583. 2008.00776.x.
42. Matambo TS, Paine MJ, Coetzee M and Koekemoer LL. Sequence characterization of cytochrome P450 CYP6P9 in pyrethroid resistant and susceptible Anopheles funestus (Diptera: Culicidae). Genet. Mol. Res. 2010;9(1):554–564. Doi:10.4238/vol9- 1gmr719.
43. Djouaka RF, Bakare AA, Coulibaly ON, Akogbeto MC, Ranson H and Hemingway J. et al. Expression of the cytochrome P450s, CYP6P3 and CYP6M2 are significantly elevated in multiple pyrethroid resistant populations of Anopheles gambiaes.s. from Southern Benin and Nigeria. BMC Genom. 2008;9:538. Doi: 10.1186/1471-2164-9-538. Doi: 10.1186/1471-2164-9-538
44. Muller P, Emma Warr, Bradley J. Stevenson, Patricia M. Pignatelli, John C. Morgan and Andrew Steven.  et al. Field-caught permethrinresistant Anopheles gambiae overexpress CYP6P3, a P450 that metabolisespyrethroids. PLoS Genet. 2008;4(11):e1000286. Doi:10.1371/journal.pgen.1000286.
45. Somwang P, Yanola J, Suwan W, Walton C, Lumjuan N and Prapanthadara LA. et al. Enzymes-based resistant mechanism in pyrethroid resistant and susceptible Aedesaegypti strains from northern Thailand. Parasitol. Res. 2011;109(3):531–537. Doi: 10.1007/s00436-011-2280-0.
46. Lumjuan N, Rajatileka S, Changsom D, Wicheer J, Leelapat P and Prapanthadara LA. et al. The role of the Aedesaegypti epsilon glutathione transferases in conferring resistance to DDT and pyrethroid insecticides. Insect Biochem. Mol. Biol. 2011;41(3):203–209. Doi:10.1016/j. ibmb.2010.12.005.
47. Muller P, Donnelly MJ and Ranson H. Transcription profiling of a recently colonisedpyrethroid resistant Anopheles gambiae strain from Ghana. BMC Genom. 2007;8:36. Doi:10.1186/1471-2164-8-36.
48. Nikou D, Ranson H and Hemingway J. An adultspecific CYP6 P450 gene is overexpressed in a pyrethroid-resistant strain of the malaria vector, Anopheles gambiae. Gene. 2003;318:91–102. Doi:10. 1016/S0378-1119(03)00763-7.
49. Muller P, Chouaibou M, Pignatelli P, Etang J, Walker ED and Donnelly MJ.  et al. Pyrethroid tolerance is associated with elevated expression of antioxidants and agricultural practice in Anopheles arabiensis sampled from an area of cotton fields in Northern Cameroon. Mol. Ecol. 2008;17:1145–1155. Doi:10.1111/j.1365-294X.2007.03617.x.
50. Stevenson BJ, Bibby J, Pigneatelli P, Muangnoicharoen, O'Neill PM and Lian LY. et al. Cytochrome P450 6M2 from the malaria vector Anopheles gambiaemetabolizes pyrethroids: sequential metabolism of deltamethrin revealed. Insect Biochem. Mol. Biol. 2011;41:492–502. Doi:10.1016/j.ibmb.2011.02.003.
51. Mitchell SN, Stevenson BJ,  Müller P, Wilding CS, Egyir-Yawson A and  Field SG. et al. Identification and validation of a gene causing cross-resistance between insecticide classes in Anopheles gambiae from Ghana. Proc. Natl Acad. Sci. USA. 2012;109:6147–6152. Doi:10.1073/pnas.1203452109.
52.  Chiu TL, Wen Z, Rupasinghe SG and Schuler MA. Comparative molecular modeling of Anopheles gambiae CYP6Z1, a mosquito P450 capable of metabolizing DDT. Proc. Natl Acad. Sci. USA. 2008;105(26):8855–8860. Doi:10.1073/pnas.0709249105.
53. Wondji CS, Irving H, Morgan J, Lobo NF, Collins FH and Hunt RH. et al. Two duplicated P450 genes are associated with pyrethroid resistance in Anopheles funestus, a major malaria vector. Genome Res. 2009;19(3):452–459. Doi:10. 1101/gr.087916.108.
54. Irving H, Riveron J, Inbrahim S, Lobo N and Wondji C. Positional cloning of rp2 QTL associates the P450 genes CYP6Z1, CYP6Z3 and CYP6M7 with pyrethroid resistance in the malaria vector Anopheles funestus. Heredity. 2012;109(6): 383–392. Doi:10.1038/hdy.2012.53.
55. Wondji CS, Morgan J, Coetzee M, Hunt RH, Steen K and Black IV WC. et al. Mapping a quantitative trait locus (QTL) conferring pyrethroidresistance in the African malaria vector Anopheles funestus. BMC Genom. 2007;8:34. Doi:10. 1186/1471-2164-8-34.
56. Cuamba N, Morgan JC, Irving H, Steven A and Wondji CS. High level of pyrethroid resistance in an Anopheles funestus population of the Chokwe District in Mozambique. PLoS ONE. 2010;5(6):e11010. Doi:10.1371/journal.pone.0011010.
57. Morgan JC, Irving H, Okedi LM, Steven A and Wondji CS. Pyrethroid resistance in an Anopheles funestus population from Uganda. PLoS ONE. 2010;5(7):e11872. Doi:10.1371/journal.pone.0011872.
58. Djouaka R, Irving H, Tukur Z and Wondji CS. Exploring mechanisms of multiple insecticide resistance in a population of the malaria vector Anopheles funestus in Benin. PLoS ONE. 2011;6(11):e27760. Doi:10.1371/journal.pone.0027760.