High pyrethroid/DDT resistance in major malaria vector Anopheles coluzzii from Niger-Delta of Nigeria is probably driven by metabolic resistance mechanisms

Abstract

Entomological surveillance of local malaria vector populations is an important component of vector control and resistance management. In this study, the resistance profile and its possible mechanisms was characterised in a field population of the major malaria vector Anopheles coluzzii from Port Harcourt, the capital of Rivers state, in the Niger-Delta Region of Nigeria. Larvae collected in Port-Harcourt, were reared to adulthood and used for WHO bioassays. The population exhibited high resistance to permethrin, deltamethrin and DDT with mortalities of 6.7% ± 2.4, 37.5% ± 3.2 and 6.3% ± 4.1, respectively, but were fully susceptible to bendiocarb and malathion. Synergist bioassays with piperonylbutoxide (PBO) partially recovered susceptibility, with mortalities increasing to 53% ± 4, indicating probable role of CYP450s in permethrin resistance (χ2 = 29.48, P < 0.0001). Transcriptional profiling revealed five major resistance-associated genes overexpressed in the field samples compared to the fully susceptible laboratory colony, Ngoussou. Highest fold change (FC) was observed with GSTe2 (FC = 3.3 in permethrin exposed and 6.2 in unexposed) and CYP6Z3 (FC = 1.4 in exposed and 4.6 in unexposed). TaqMan genotyping of 32 F0 females detected the 1014F and 1575Y knockdown resistance (kdr) mutations with frequencies of 0.84 and 0.1, respectively, while 1014S mutation was not detected. Sequencing of a fragment of the voltage-gated sodium channel, spanning exon 20 from 13 deltamethrin-resistant and 9 susceptible females revealed only 2 distinct haplotypes with a low haplotype diversity of 0.33. The findings of high pyrethroid resistance but with a significant degree of recovery after PBO synergist assay suggests the need to move to PBO-based nets. This could be complemented with carbamate- or organophosphate-based indoor residual spraying in this area.

Susceptibility status of Anopheles gambiae complex in NNEWI community, Anambra state

“…However, the carbamate insecticides (bendiocarb, and propoxur) particularly bendiocarb as observed in the present study may be a useful alternative chemical class to organochlorine (DDT) and the pyrethroids (deltermathrin and permethrin) for vector control. This has also been suggested by Muhammad et al (2021) [17] with continuous monitoring through bioassay of the carbamate insecticides. This investigation did not involve studies on mechanisms conferring resistance in An.…”

“…gambiae mosquitoes to DDT, pyrethroid, and organophosphate were reported in Amansea community (Nwankwo et al,) [19] . Household and agricultural use of these insecticides have been implicated in the occurrence of resistance in the [17,18,20,7] . In addition, there have been two major rounds of LLINs mass distribution and IRS campaigns conducted between 2009 and 2014 in Anambra State.…”

Use of Novel Lab-Assays to Examine the Effect of Pyrethroid-Treated Bed Nets on Blood Feeding Success and Longevity of Highly Insecticide-Resistant Anopheles Gambiae S.I. Mosquitoes.

“…The experiments also highlight the fact that the standard WHO test procedures for evaluating resistance and measuring the bio-e cacy of ITNs [16,43] are weak indicators of how ITNs ultimately determine malaria transmission risk, and hence for understanding the functional signi cance of insecticide resistance. The WHO resistance assay uses tubes (as used in the initial assays here) to force mosquitoes into contact with lter paper treated with diagnostic doses of insecticide for 1h [44][45][46].The WHO ITN bioe cacy assay uses cones to force mosquitoes into contact with ITNs for 3 minutes [47][48][49]. Neither assay simulates how mosquitoes contact ITNs during host searching and blood feeding in nature [26].…”

Potential of Essential Oil-Based Anticholinesterase Insecticides against Anopheles Vectors: A Review

“…This antagonizes the action of pyrethroids and organochlorines since these compounds bind to open sodium channels [ 25 , 41 , 46 , 47 ]. Apart from the kdr mutations, elevated metabolic enzymes, including P450 monooxygenases, glutathione-S-transferases and non-specific esterases, also convey high resistance to pyrethroids and organochlorides [ 13 , 39 , 40 , 44 , 48 , 49 ]. On the other hand, the resistance mechanism commonly conferring organophosphate and carbamate resistance is a single point polymorphism resulting from glycine conversion to a serine residue at position 119 (G119S; Torpedo californica AChE numbering) or more precisely, position 280 (G280S; Anopheles gambiae AChE numbering) in the AChE target [ 41 , 47 , 50 , 51 ].…”

“…The implementation of large-scale larviciding is however challenging in Sub-Saharan Africa and these may be used as a complementary intervention [ 6 , 9 , 10 , 11 ]. The Anopheles vectors have developed substantial resistance against almost all current insecticides [ 12 , 13 , 14 , 15 ]. To compound the issue, the commercial development of insecticides through various and often complicated synthetic mechanisms is expensive and time-consuming [ 16 , 17 ].…”