Species composition and insecticide resistance in malaria vectors in Ellibou, southern Côte d’Ivoire and first finding of Anopheles arabiensis in Côte d’Ivoire

N'Dri, Bédjou P; Wipf, Nadja; Saric, Jasmina; Fodjo, Behi K.; Raso, Giovanna; Utzinger, Jürg; Müller, Pie; Mouhamadou, Chouaïbou S.

doi:10.1186/s12936-023-04456-y

Cited by 8 publications

(2 citation statements)

References 61 publications

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“…coluzzii with the former available in higher overall proportions and at most time points except in the middle of the dry season. This nding con rms several studies that have demonstrated that both species commonly occur in sympatry in West Africa, though they may differ substantially in their ecological behaviour, insecticide resistance status and vectorial capacity [45][46][47]. Previous entomological surveys in Benin have also shown a wide variability in the proportion of both sibling species in terms of geographical spread and seasons with reports of higher densities of An.…”

Section: Discussionsupporting

confidence: 83%

Malaria prevalence and transmission in the Zakpota sub-district of central Benin: baseline characteristics for a community randomised trial of a new insecticide for indoor residual spraying

Govoetchan,

Fongnikin,

Hueha

et al. 2024

Preprint

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Introduction: Malaria transmission is known to be perennial and heterogeneous in Benin. Studies assessing local malaria prevalence, transmission levels and vector characteristics are critical for designing, monitoring and evaluating new vector control interventions in community trials. We conducted a study in the Zakpota sub-district of central Benin to collect baseline data on household characteristics, malaria prevalence, vector characteristics and transmission dynamics in preparation for a randomised controlled trial to evaluate the community impact of VECTRON™ T500, a new broflanilide indoor residual spraying (IRS) product. Method A total of 480 children under 5 years of age from the 15 villages of the sub-district were tested for malaria by rapid diagnostic tests (RDTs). Mosquitoes were collected by human landing catches (HLCs), pyrethrum spray catches (PSCs) and Centers for Disease Control miniature light traps (CDC-LTs) in selected houses in each village to assess vector density, composition, vector infectivity and prevalence insecticide resistance markers. Bioassays were performed to detect vector susceptibility to pyrethroids, broflanilide (6µg/bottle) and clothianidin (90µg /bottle). Results A total of 9,080 households were enumerated in the 15 study villages. Insecticide-treated net (ITN) usage was > 90% with 1–2 ITNs owned per household. Houses were constructed mainly with cement (44%) and mud (38%) substrates or a mixture of cement and mud (18%) and 60% of them had open eaves. The overall prevalence of P. falciparum infection was 19% among surveyed children; 20% among females and 18% among males. The haemoglobin rate showed an anaemia (< 11 g/dL) prevalence of 66%. An. coluzzii and An. gambiae s.s. were the two vector species present at an overall proportion of 46% vs. 54% respectively. The human biting rate was 2.3 bites per person per night (b/p/n) and biting occurred mostly indoors compared to outdoors (IRR = 0.776; p = 0.001). The overall proportion of outdoor biting was 44% and exceeded indoor biting in 3 villages. The sporozoite rate was 2% with a combined monthly entomological inoculation rate (EIR) of 16.1 infected bites per person per year (ib/p/y). There was great variability in malaria transmission risk across the villages with EIR ranging from 0-29.3 ib/p/y. The vector population showed a high intensity of resistance to pyrethroids across the study villages but was largely susceptible to broflanilide and clothianidin. Conclusion This study found high levels of malaria prevalence, vector density and transmission in the Zakpota sub-district despite the high use of insecticide-treated nets. The vector population was mostly indoor resting and showed a high intensity of pyrethroid resistance but was generally fully susceptible to broflanilide. These findings demonstrated the suitability of the study area for the assessment of VECTRON™ T500 in a community randomised trial.

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Section: Discussionsupporting

confidence: 83%

Malaria prevalence and transmission in the Zakpota sub-district of central Benin: baseline characteristics for a community randomised trial of a new insecticide for indoor residual spraying

Govoetchan,

Fongnikin,

Hueha

et al. 2024

Preprint

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“…Notably, this species has been found adapting in more polluted breeding sites associated with urbanization, unlike An. gambiae, which prefers small, temporary, sunlit, and clear freshwater pools, typical habitats found in rural areas (43,(45)(46)(47).…”

Section: Discussionmentioning

confidence: 99%

Insecticide resistance and its intensity in urbanAnopheles arabiensisin Kisumu City, Western Kenya:Implications for malaria control in urban areas

Machani,

Nzioki,

Onyango

et al. 2024

Preprint

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Background: The rise of insecticide resistance poses a growing challenge to the effectiveness of vector control tools, particularly in rural areas. However, the urban setting has received comparatively less focus despite its significance in attracting rural to urban migration. Unplanned urbanization, often overlooked, exacerbates insecticide resistance as Anopheles mosquitoes adapt to the polluted environments of rapidly expanding cities. This study aimed to assess the insecticide susceptibility status of malaria vectors and identify potential underlying mechanisms across three distinct ecological settings characterized by differing levels of urbanization in Kisumu County, Kenya. Methods: Field-derived An. gambiae (s.l.) larvae collected from a long stretch of urban-to-rural continuum were phenotyped as either resistant or susceptible to six different insecticides using the World Health Organization (WHO) susceptibility test. Polymerase chain reaction (PCR) techniques were used to identify the species of the An. gambiae complex and screened for mutations at voltage-gated sodium channels (Vgsc-1014F, Vgsc-1014S, Vgsc-1575Y) and acetylcholinesterase Ace1-119S. Metabolic enzymes activities (non-specific β-esterases and monooxygenases) were evaluated in mosquitoes not exposed to insecticides using microplate assays. Additionally, during larval sampling, a retrospective questionnaire survey was conducted to determine pesticide usage by the local inhabitants. Results: Anopheles arabiensis dominated in urban (96.2%) and peri-urban (96.8%) areas, while An. gambiae (s.s.) was abundant in rural settings (82.7%). Urban mosquito populations showed high resistance intensity to deltamethrin (mortality rate: 85.2% at 10x) and suspected resistance to pirimiphos-methyl and bendiocarb while peri-urban and rural populations exhibited moderate resistance intensity to deltametrin (mortality rate >98% at 10x). Preexposure of mosquitoes to a synergist piperonyl butoxide (PBO) significantly increased mortality rates: from 40.7% to 88.5% in urban, 51.9% to 90.3% in peri-urban, and 55.4% to 87.6% in rural populations for deltamethrin, and from 41.4% to 78.8% in urban, 43.7% to 90.7% in peri-urban, and 35% to 84.2% in rural populations for permethrin. In contrast, 100% mortality to chlorfenapyr and clothianidin was observed in all the populations tested. The prevalence of L1014F mutation was notably higher in urban An. arabiensis (0.22) unlike the peri-urban (0.11) and rural (0.14) populations while the L1014S mutation was more prevalent in rural An. gambiae (0.93). Additionally, urban An. arabiensis exhibited elevated levels of mixed function oxidases (0.8/mg protein) and non-specific esterases (2.12/mg protein) compared to peri-urban (0.57/mg protein and 1.5/mg protein, respectively) and rural populations (0.6/mg protein and 1.8/mg protein, respectively). Pyrethroids, apart from their use in public health through LLINs, were being highly used for agricultural purposes across all ecological settings (urban 38%, peri-urban 36% and rural 37%) followed by amidine group, with organophosphates, neonicotinoids and carbamates being of secondary importance. Conclusion: These findings show high resistance of An. arabiensis to insecticides commonly used for vector control, linked with increased levels of detoxification enzymes. The observed intensity of resistance underscores the pressing issue of insecticide resistance in urban areas, potentially compromising the effectiveness of vector control measures, especially pyrethroid-treated LLINs. Given the species' unique behavior and ecology compared to An. gambiae, tailored vector control strategies are needed to address this concern in urban settings.

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Recessivity of deltamethrin resistance, kdr mutations, and detoxifying enzymes in hybrids of Triatoma phyllosoma subcomplex from Mexico

Davila-Barboza,

Gutierrez-Rodriguez,

Lopez-Monroy

et al. 2024

Parasitol Res

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Species composition and insecticide resistance in malaria vectors in Ellibou, southern Côte d’Ivoire and first finding of Anopheles arabiensis in Côte d’Ivoire

Cited by 8 publications

References 61 publications

Malaria prevalence and transmission in the Zakpota sub-district of central Benin: baseline characteristics for a community randomised trial of a new insecticide for indoor residual spraying

Malaria prevalence and transmission in the Zakpota sub-district of central Benin: baseline characteristics for a community randomised trial of a new insecticide for indoor residual spraying

Insecticide resistance and its intensity in urbanAnopheles arabiensisin Kisumu City, Western Kenya:Implications for malaria control in urban areas

Recessivity of deltamethrin resistance, kdr mutations, and detoxifying enzymes in hybrids of Triatoma phyllosoma subcomplex from Mexico

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