Time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes
Abstract Background Increasing metabolic resistance in malaria vector mosquitoes resulted in the development of insecticide-treated nets (ITNs) with active ingredients (AI) that target them. Bioassays that accurately measure the mortality induced by these AIs on ITNs are needed. Mosquito metabolic e...
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| Format: | Article |
| Language: | English |
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BMC
2024-03-01
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| Series: | Parasites & Vectors |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s13071-024-06190-z |
| _version_ | 1797275711375933440 |
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| author | Olukayode G. Odufuwa John Bradley Safina Ngonyani Ahmadi Bakari Mpelepele Isaya Matanila Joseph B. Muganga Rune Bosselmann Ole Skovmand Zawadi Mageni Mboma Sarah Jane Moore |
| author_facet | Olukayode G. Odufuwa John Bradley Safina Ngonyani Ahmadi Bakari Mpelepele Isaya Matanila Joseph B. Muganga Rune Bosselmann Ole Skovmand Zawadi Mageni Mboma Sarah Jane Moore |
| author_sort | Olukayode G. Odufuwa |
| collection | DOAJ |
| description | Abstract Background Increasing metabolic resistance in malaria vector mosquitoes resulted in the development of insecticide-treated nets (ITNs) with active ingredients (AI) that target them. Bioassays that accurately measure the mortality induced by these AIs on ITNs are needed. Mosquito metabolic enzyme expression follows a circadian rhythm. Thus, this study assessed (i) influence of the time of day of mosquito exposure and (ii) timing of assessment of mortality post exposure (24 and 72 h) to ITNs against vectors that are susceptible to pyrethroids and those with metabolic and knockdown resistance mechanisms. Methods Two cone bioassay experiments were conducted following World Health Organization (WHO) guidelines. Firstly, on ITNs incorporated with 2 g AI/kg of deltamethrin (DM) alone, or combined with 8 g AI/kg piperonyl butoxide (PBO) synergist, during the day (9:00–14:00 h) and repeated in the evening (18:00–20:00 h). This was followed by a confirmatory experiment during the afternoon (12:00–14:00 h) and repeated in the night (22:00–24:00 h) using mosquitoes unexposed or pre-exposed to PBO for 1 h before exposure to DM ITNs. Each net piece was tested with a minimum of eight cones per time (N = 24). The outcome was mortality after 24 h (M24) or 72 h (M72) of holding. Results The cone bioassays performed using metabolic resistant mosquitoes during the evening showed significantly lower M24 than those performed in the day for DM: odds ratio (OR) 0.14 [95% confidence interval (CI) 0.06–0.30, p < 0.0001] and DM PBO [OR 0.29 (95% CI 0.18—0.49, p < 0.0001). M72 was higher than M24 for metabolic resistant mosquitoes exposed to DM [OR 1.44 (95% CI 1.09–1.88), p = 0.009] and DM PBO [OR 1.82 (95% CI 1.42–2.34), p < 0.0001]. An influence of hour of experiment and time of assessment was not observed for mosquitoes that had knockdown resistance or that were pyrethroid-susceptible. Conclusions Time of day of experiment and hour of assessment of delayed mortality after exposure of mosquitoes are important considerations in evaluating insecticides that interact with mosquito metabolism to counter metabolic resistant mosquitoes. This is important when evaluating field-aged ITNs that may have lower concentrations of AI. Graphical Abstract |
| first_indexed | 2024-03-07T15:18:25Z |
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| id | doaj.art-c8c29a4f852640a7a9c15db9aaa0ec30 |
| institution | Directory Open Access Journal |
| issn | 1756-3305 |
| language | English |
| last_indexed | 2024-03-07T15:18:25Z |
| publishDate | 2024-03-01 |
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| spelling | doaj.art-c8c29a4f852640a7a9c15db9aaa0ec302024-03-05T17:50:35ZengBMCParasites & Vectors1756-33052024-03-0117111110.1186/s13071-024-06190-zTime of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoesOlukayode G. Odufuwa0John Bradley1Safina Ngonyani2Ahmadi Bakari Mpelepele3Isaya Matanila4Joseph B. Muganga5Rune Bosselmann6Ole Skovmand7Zawadi Mageni Mboma8Sarah Jane Moore9Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological SciencesMRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine (LSHTM)Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological SciencesVector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological SciencesVector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological SciencesVector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological SciencesVegro ApsMCC47Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological SciencesVector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological SciencesAbstract Background Increasing metabolic resistance in malaria vector mosquitoes resulted in the development of insecticide-treated nets (ITNs) with active ingredients (AI) that target them. Bioassays that accurately measure the mortality induced by these AIs on ITNs are needed. Mosquito metabolic enzyme expression follows a circadian rhythm. Thus, this study assessed (i) influence of the time of day of mosquito exposure and (ii) timing of assessment of mortality post exposure (24 and 72 h) to ITNs against vectors that are susceptible to pyrethroids and those with metabolic and knockdown resistance mechanisms. Methods Two cone bioassay experiments were conducted following World Health Organization (WHO) guidelines. Firstly, on ITNs incorporated with 2 g AI/kg of deltamethrin (DM) alone, or combined with 8 g AI/kg piperonyl butoxide (PBO) synergist, during the day (9:00–14:00 h) and repeated in the evening (18:00–20:00 h). This was followed by a confirmatory experiment during the afternoon (12:00–14:00 h) and repeated in the night (22:00–24:00 h) using mosquitoes unexposed or pre-exposed to PBO for 1 h before exposure to DM ITNs. Each net piece was tested with a minimum of eight cones per time (N = 24). The outcome was mortality after 24 h (M24) or 72 h (M72) of holding. Results The cone bioassays performed using metabolic resistant mosquitoes during the evening showed significantly lower M24 than those performed in the day for DM: odds ratio (OR) 0.14 [95% confidence interval (CI) 0.06–0.30, p < 0.0001] and DM PBO [OR 0.29 (95% CI 0.18—0.49, p < 0.0001). M72 was higher than M24 for metabolic resistant mosquitoes exposed to DM [OR 1.44 (95% CI 1.09–1.88), p = 0.009] and DM PBO [OR 1.82 (95% CI 1.42–2.34), p < 0.0001]. An influence of hour of experiment and time of assessment was not observed for mosquitoes that had knockdown resistance or that were pyrethroid-susceptible. Conclusions Time of day of experiment and hour of assessment of delayed mortality after exposure of mosquitoes are important considerations in evaluating insecticides that interact with mosquito metabolism to counter metabolic resistant mosquitoes. This is important when evaluating field-aged ITNs that may have lower concentrations of AI. Graphical Abstracthttps://doi.org/10.1186/s13071-024-06190-zInsecticideDeltamethrinPyrethroidPiperonyl butoxide (PBO)Cone bioassayTime |
| spellingShingle | Olukayode G. Odufuwa John Bradley Safina Ngonyani Ahmadi Bakari Mpelepele Isaya Matanila Joseph B. Muganga Rune Bosselmann Ole Skovmand Zawadi Mageni Mboma Sarah Jane Moore Time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes Parasites & Vectors Insecticide Deltamethrin Pyrethroid Piperonyl butoxide (PBO) Cone bioassay Time |
| title | Time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes |
| title_full | Time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes |
| title_fullStr | Time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes |
| title_full_unstemmed | Time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes |
| title_short | Time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes |
| title_sort | time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes |
| topic | Insecticide Deltamethrin Pyrethroid Piperonyl butoxide (PBO) Cone bioassay Time |
| url | https://doi.org/10.1186/s13071-024-06190-z |
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