The relationship between Anopheles gambiae density and rice cultivation in the savannah zone and forest zone of Cote d'Ivoire

Abstract Routine monitoring of occurrence, levels and mechanisms of insecticide resistance informs effective management strategies, and should be used to assess the effect of new tools on resistance. As part of a cluster randomised controlled trial evaluating a novel insecticide-based intervention in central Côte d’Ivoire, we assessed resistance and its underlying mechanisms in Anopheles gambiae populations from a subset of trial villages. Resistance to multiple insecticides in An. gambiae s.s. and An. coluzzii was detected across villages, with dose–response assays demonstrating extremely high resistance intensity to the pyrethroid deltamethrin (> 1,500-fold), and mortality following exposure to pyrethroid-treated bednets was low (< 30% mortality in cone bioassays). The 1014F kdr mutation was almost fixed (≥ 90%) in all villages but the 1575Y kdr-amplifying mutation was relatively rare (< 15%). The carbamate and organophosphate resistance-associated Ace-1 G119S mutation was also detected at moderate frequencies (22–43%). Transcriptome analysis identified overexpression of P450 genes known to confer pyrethroid resistance (Cyp9K1, Cyp6P3, and Cyp6M2), and also a carboxylesterase (COEAE1F) as major candidates. Cyp6P3 expression was high but variable (up to 33-fold) and correlated positively with deltamethrin resistance intensity across villages (r2 = 0.78, P = 0.02). Tools and strategies to mitigate the extreme and multiple resistance provided by these mechanisms are required in this area to avoid future control failures.

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Étude du niveau de production larvaire d’Anopheles gambiae s.l. (Diptera: Culicidae) dans différents types de gîtes à Oussou-yaokro au Centre-Ouest et à Korhogo, au Nord (Côte d’Ivoire).

Journal of Applied Biosciences ◽

10.4314/jab.v105i1.13 ◽

2016 ◽

Vol 105 (1) ◽

pp. 10170 ◽

Cited By ~ 1

Author(s):

Tia Emmanuel Gbalegba ◽

N.G. Constant M'Bra ◽

K. Richard Kaba ◽

Aboudramane Boby ◽

O.A Marie Koné ◽

...

Keyword(s):

Anopheles Gambiae ◽

Cote D'ivoire ◽

Côte D’Ivoire ◽

Cote D’Ivoire ◽

Côte D'ivoire

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Susceptibility of Anopheles gambiae from Côte d’Ivoire to insecticides used on insecticide-treated nets: evaluating the additional entomological impact of piperonyl butoxide and chlorfenapyr

Malaria Journal ◽

10.1186/s12936-020-03523-y ◽

2020 ◽

Vol 19 (1) ◽

Author(s):

Bernard L. Kouassi ◽

Constant Edi ◽

Emmanuel Tia ◽

Lucien Y. Konan ◽

Maurice A. Akré ◽

...

Keyword(s):

Anopheles Gambiae ◽

Cote D'ivoire ◽

Côte D’Ivoire ◽

Resistance Management ◽

Piperonyl Butoxide ◽

Assay Method ◽

Insecticide Treated Nets ◽

Cote D’Ivoire ◽

Pyrethroid Insecticides ◽

Côte D'ivoire

Abstract Background Pyrethroid-treated mosquito nets are currently the mainstay of vector control in Côte d’Ivoire. However, resistance to pyrethroids has been reported across the country, limiting options for insecticide resistance management due to the paucity of alternative insecticides. Two types of insecticide-treated nets (ITNs), ITNs with pyrethroids and the synergist piperonyl butoxide (PBO), and Interceptor®G2 nets, a net treated with a combination of chlorfenapyr and alpha-cypermethrin, are believed to help in the control of pyrethroid-resistant mosquitoes. Methods The susceptibility of Anopheles gambiae sensu lato (s.l.) to pyrethroid insecticides with and without pre-exposure to PBO as well as to chlorfenapyr was investigated in fifteen sites across the country. Susceptibility tests were conducted on 2- to 4-day old adult female An. gambiae s.l. reared from larval collections. The resistance status, intensity, and effects of PBO on mortality after exposure to different concentrations of deltamethrin, permethrin and alpha-cypermethrin were determined using WHO susceptibility test kits. In the absence of a WHO-recommended standard protocol for chlorfenapyr, two interim doses (100 and 200 µg/bottle) were used to test the susceptibility of mosquitoes using the CDC bottle assay method. Results Pre-exposure to PBO did not result in full restoration of susceptibility to any of the three pyrethroids for the An. gambiae s.l. populations from any of the sites surveyed. However, PBO pre-exposure did increase mortality for all three pyrethroids, particularly deltamethrin (from 4.4 to 48.9%). Anopheles gambiae s.l. from only one site (Bettie) were susceptible to chlorfenapyr at the dose of 100 µg active ingredient (a.i.)/bottle. At the dose of 200 µg (a.i.)/bottle, susceptibility was only recorded in 10 of the 15 sites. Conclusion Low mosquito mortality was found for pyrethroids alone, and while PBO increased mortality, it did not restore full susceptibility. The vector was not fully susceptible to chlorfenapyr in one third of the sites tested. However, vector susceptibility to chlorfenapyr seems to be considerably higher than for pyrethroids alone or with PBO. These data should be used cautiously when making ITN procurement decisions, noting that bioassays are conducted in controlled conditions and may not fully represent field efficacy where the host-seeking behaviours, which include free-flying activity are known to enhance pro-insecticide chlorfenapyr intoxication to mosquitoes.

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Assessing Anopheles vector species diversity and transmission of malaria in four health districts along the borders of Côte d’Ivoire

Malaria Journal ◽

10.1186/s12936-021-03938-1 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Firmain N. Yokoly ◽

Julien B. Z. Zahouli ◽

Graham Small ◽

Allassane F. Ouattara ◽

Millicent Opoku ◽

...

Keyword(s):

Species Diversity ◽

Anopheles Gambiae ◽

Cote D'ivoire ◽

Côte D’Ivoire ◽

Malaria Incidence ◽

Vector Species ◽

Cote D’Ivoire ◽

Côte D'ivoire ◽

Health Districts ◽

Sporozoite Infection

Abstract Background Although malaria and Anopheles mosquito vectors are highly prevalent in Côte d’Ivoire, limited data are available to help understand the malaria vector density and transmission dynamics in areas bordering the country. To address this gap, the Anopheles mosquito species diversity, the members of the Anopheles gambiae complex and the transmission of malaria were assessed in four health districts along the borders of Côte d’Ivoire. Methods From July 2016 through December 2016 and July 2017 through December 2017, adult Anopheles mosquitoes were collected in four health districts of Côte d’Ivoire (Aboisso, Bloléquin, Odienné and Ouangolodougou) using standardized window exit trap (WET) and pyrethrum knockdown spray collection (PSC) methods. The collected mosquitoes were identified morphologically at species level and the members of the An. gambiae complex were separated using short interspersed nuclear element-based polymerase chain reaction (SINE-PCR). Anopheles gambiae sensu lato (s.l.), Anopheles funestus s.l. and Anopheles nili specimens were analysed for malaria Plasmodium parasite detection using the cytochrome oxidase I gene (COX-I), and malaria prevalence among human population through local Ministry of Health (MoH) statistical yearbooks. Results A total of 281 female Anopheles were collected in Aboisso, 754 in Bloléquin, 1319 in Odienné and 2443 in Ouangolodougou. Seven Anopheles species were recorded including An. gambiae s.l. (94.8–99.1%) as the main vector, followed by An. funestus s.l. (0.4–4.3%) and An. nili (0–0.7%). Among An. gambiae s.l., Anopheles coluzzii represented the predominant species in Aboisso (89.2%) and Bloléquin (92.2%), while An. gambiae sensu stricto (s.s.) was the major species in Odienné (96.0%) and Ouangolodougou (94.2%). The Plasmodium sporozoite infection rate in An. gambiae s.l. was highest in Odienné (11.0%; n = 100) followed by Bloléquin (7.8%, n = 115), Aboisso (3.1%; n = 65) and Ouangologoudou (2.5%; n = 120). In An. funestus s.l., Plasmodium falciparum sporozoite infection rate was estimated at 6.2% (n = 32) in Bloléquin, 8.7% (n = 23) in Odienné. No An. funestus s.l. specimens were found infected with P. falciparum sporozoite infection in Ouangolodougou and Aboisso. No P. falciparum sporozoite was detected in An. nili specimens in the four health districts. Among the local human populations, malaria incidence was higher in Odienné (39.7%; n = 45,376) and Bloléquin (37.6%; n = 150,205) compared to that in Ouangolodougou (18.3%; n = 131,629) and Aboisso (19.7%; n = 364,585). Conclusion Anopheles vector species diversity, abundance and Plasmodium sporozoite infection were high within the health districts along the borders of the country of Côte d’Ivoire, resulting in high malaria transmission among the local populations. Anopheles gambiae s.l. and An. funestus s.l. were found to be highly infected with Plasmodium in the health districts of Bloléquin and Odienné where higher malaria incidence was observed than the other districts. This study provides important information that can be used to guide Côte d’Ivoire National Malaria Control Programme for vector control decision-making, mainly in districts that are at the country borders.

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First report of the East African kdr mutation in an Anopheles gambiae mosquito in Côte d’Ivoire

Wellcome Open Research ◽

10.12688/wellcomeopenres.10662.1 ◽

2017 ◽

Vol 2 ◽

pp. 8 ◽

Cited By ~ 4

Author(s):

Mouhamadou Chouaïbou ◽

Fodjo Behi Kouadio ◽

Emmanuel Tia ◽

Luc Djogbenou

Keyword(s):

Anopheles Gambiae ◽

East Africa ◽

Cote D'ivoire ◽

Côte D’Ivoire ◽

Sub Saharan Africa ◽

Taqman Assay ◽

East African ◽

Cote D’Ivoire ◽

Côte D'ivoire ◽

Genotype Frequencies

Background. The intensive use of insecticides in public health and agriculture has led to the development of insecticide resistances in malaria vectors across sub-Saharan Africa countries in the last two decades. The kdr target site point mutation which is among the best characterised resistance mechanisms seems to be changing its distribution patterns on the African continent. The 1014F kdr mutation originally described only in West Africa is spreading to East Africa while the 1014S kdr mutation originally described in East Africa, is spreading to West and Central Africa. However, the East-kdr mutation has not been reported in Côte d'Ivoire so far. Methods. Immature stages of Anopheles gambiae s.l. were collected from breeding sites at the outskirts of Yamoussoukro, Côte d'Ivoire. Emerging 3–5 day old adult female mosquitoes were tested for susceptibility to deltamethrin 0.05%, malathion 5%, bendiocarb 1% and dichlorodiphenyltrichloroethane (DDT) 4% according to WHO standard procedures. A total of 50 An. gambiae s.l. specimens were drawn at random for DNA extraction and identification down to the species level. A subsample of 30 mosquitoes was tested for the East-African kdr mutation using a Taqman assay. Results. The tested mosquito population appeared to be strongly resistant to deltamethrin (1.03% mortality), bendiocarb (38.46% mortality) and DDT (0% mortality) with probable resistance observed for malathion (92.47%). Among the 41 mosquitoes that were successfully characterized, An. coluzzii was predominant (68.3%) followed by An. gambiae s.s. (19.5%) and a few hybrids (7.3%). Out of 30 specimens genotyped for East-kdr, a single hybrid mosquito appeared to be heterozygous for the mutation. Conclusion. The present study revealed the presence of the East-kdr mutation in Côte d’Ivoire for the first time in An. gambiae and highlights the urgent need to start monitoring the allele and genotype frequencies.

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Susceptibility of Anopheles gambiae sensu lato from Côte d’Ivoire to insecticides used on insecticide-treated nets: evaluating the additional entomological impact of piperonyl butoxide and chlorfenapyr

10.21203/rs.3.rs-21138/v2 ◽

2020 ◽

Author(s):

Bernard L. Kouassi ◽

Constant Edi ◽

Emmanuel Tia ◽

Lucien Y. Konan ◽

Maurice A. Akré ◽

...

Keyword(s):

Anopheles Gambiae ◽

Cote D'ivoire ◽

Côte D’Ivoire ◽

Resistance Management ◽

Piperonyl Butoxide ◽

Assay Method ◽

Insecticide Treated Nets ◽

Cote D’Ivoire ◽

Pyrethroid Insecticides ◽

Côte D'ivoire

Abstract BackgroundPyrethroid-treated mosquito nets are currently the mainstay of vector control in Côte d’Ivoire. However, resistance to pyrethroids has been reported across the country, limiting options for insecticide resistance management due to the paucity of alternative insecticides. Two types of insecticide-treated nets (ITNs), ITNs with pyrethroids and the synergist piperonyl butoxide (PBO), and Interceptor®G2 nets, a net treated with a combination of chlorfenapyr and alpha-cypermethrin, are believed to help in the control of pyrethroid-resistant mosquitoes. MethodsThe susceptibility of Anopheles gambiae sensu lato (s.l.) to pyrethroid insecticides with and without pre-exposure to PBO as well as to chlorfenapyr was investigated in fifteen sites across the country. Susceptibility tests were conducted on 2- to 4-day old adult female An. gambiae s.l. reared from larval collections. The resistance status, intensity, and effects of PBO on mortality after exposure to different concentrations of deltamethrin, permethrin and alpha-cypermethrin were determined using WHO susceptibility test kits. In the absence of a WHO-recommended standard protocol for chlorfenapyr, two interim doses (100 and 200 µg/bottle) were used to test the susceptibility of mosquitoes using the CDC bottle assay method. ResultsPre-exposure to PBO did not result in full restoration of susceptibility to any of the three pyrethroids for the An. gambiae s.l. populations from any of the sites surveyed. However, PBO pre-exposure did increase mortality for all three pyrethroids, particularly deltamethrin (from 4.4% to 48.9%). Anopheles gambiae s.l. from only one site (Bettie) were susceptible to chlorfenapyr at the dose of 100 µg active ingredient (a.i.)/bottle. At the dose of 200 µg (a.i.)/bottle, susceptibility was only recorded in 10 of the 15 sites.ConclusionLow mosquito mortality was found for pyrethroids alone, and while PBO increased mortality, it did not restore full susceptibility. The vector was not fully susceptible to chlorfenapyr in one third of the sites tested. However, vector susceptibility to chlorfenapyr seems to be considerably higher than for pyrethroids alone or with PBO. These data should be used cautiously when making ITN procurement decisions, noting that bioassays are conducted in controlled conditions and may not fully represent field efficacy where the host-seeking behaviors which include free-flying activity are known to enhance pro-insecticide chlorfenapyr intoxication to mosquitoes.

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