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Tchouakui M, Thiomela RF, Nchoutpouen E, Menze BD, Ndo C, Achu D, Tabue RN, Njiokou F, Joel A, Wondji CS. High efficacy of chlorfenapyr-based net Interceptor ® G2 against pyrethroid-resistant malaria vectors from Cameroon. Infect Dis Poverty 2023; 12:81. [PMID: 37641108 PMCID: PMC10463949 DOI: 10.1186/s40249-023-01132-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 08/21/2023] [Indexed: 08/31/2023] Open
Abstract
BACKGROUND The increasing reports of resistance to pyrethroid insecticides associated with reduced efficacy of pyrethroid-only interventions highlight the urgency of introducing new non-pyrethroid-only control tools. Here, we investigated the performance of piperonyl-butoxide (PBO)-pyrethroid [Permanet 3.0 (P3.0)] and dual active ingredients (AI) nets [Interceptor G2 (IG2): containing pyrethroids and chlorfenapyr and Royal Guard (RG): containing pyrethroids and pyriproxyfen] compared to pyrethroid-only net Royal Sentry (RS) against pyrethroid-resistant malaria vectors in Cameroon. METHODS The efficacy of these tools was firstly evaluated on Anopheles gambiae s.l. and Anopheles funestus s.l. from Gounougou, Mibellon, Mangoum, Nkolondom, and Elende using cone/tunnel assays. In addition, experimental hut trials (EHT) were performed to evaluate the performance of unwashed and 20 times washed nets in semi-field conditions. Furthermore, pyrethroid-resistant markers were genotyped in dead vs alive, blood-fed vs unfed mosquitoes after exposure to the nets to evaluate the impact of these markers on net performance. The XLSTAT software was used to calculate the various entomological outcomes and the Chi-square test was used to compare the efficacy of various nets. The odds ratio and Fisher exact test were then used to establish the statistical significance of any association between insecticide resistance markers and bed net efficacy. RESULTS Interceptor G2 was the most effective net against wild pyrethroid-resistant An. funestus followed by Permanet 3.0. In EHT, this net induced up to 87.8% mortality [95% confidence interval (CI): 83.5-92.1%) and 55.6% (95% CI: 48.5-62.7%) after 20 washes whilst unwashed pyrethroid-only net (Royal Sentry) killed just 18.2% (95% CI: 13.4-22.9%) of host-seeking An. funestus. The unwashed Permanet 3.0 killed up to 53.8% (95% CI: 44.3-63.4%) of field-resistant mosquitoes and 47.2% (95% CI: 37.7-56.7%) when washed 20 times, and the Royal Guard 13.2% (95% CI: 9.0-17.3%) for unwashed net and 8.5% (95% CI: 5.7-11.4%) for the 20 washed net. Interceptor G2, Permanet 3.0, and Royal Guard provided better personal protection (blood-feeding inhibition 66.2%, 77.8%, and 92.8%, respectively) compared to pyrethroid-only net Royal Sentry (8.4%). Interestingly, a negative association was found between kdrw and the chlorfenapyr-based net Interceptor G2 (χ2 = 138; P < 0.0001) with homozygote-resistant mosquitoes predominantly found in the dead ones. CONCLUSIONS The high mortality recorded with Interceptor G2 against pyrethroid-resistant malaria vectors in this study provides first semi-field evidence of high efficacy against these major malaria vectors in Cameroon encouraging the implementation of this novel net for malaria control in the country. However, the performance of this net should be established in other locations and on other major malaria vectors before implementation at a large scale.
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Affiliation(s)
- Magellan Tchouakui
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon.
| | - Riccado F Thiomela
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Elysee Nchoutpouen
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
| | - Benjamin D Menze
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
| | - Cyrille Ndo
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 24157, Douala, Cameroon
| | - Dorothy Achu
- Ministry of Public Health, National Malaria Control Programme, P.O. Box 14386, Yaounde, Cameroon
| | - Raymond N Tabue
- Ministry of Public Health, National Malaria Control Programme, P.O. Box 14386, Yaounde, Cameroon
| | - Flobert Njiokou
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Ateba Joel
- Ministry of Public Health, National Malaria Control Programme, P.O. Box 14386, Yaounde, Cameroon
| | - Charles S Wondji
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon.
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L35QA, UK.
- International Institute of Tropical Agriculture (IITA), P.O. Box 2008, Yaoundé, Cameroon.
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Menze BD, Mugenzi LMJ, Tchouakui M, Wondji MJ, Tchoupo M, Wondji CS. Experimental Hut Trials Reveal That CYP6P9a/b P450 Alleles Are Reducing the Efficacy of Pyrethroid-Only Olyset Net against the Malaria Vector Anopheles funestus but PBO-Based Olyset Plus Net Remains Effective. Pathogens 2022; 11:pathogens11060638. [PMID: 35745492 PMCID: PMC9228255 DOI: 10.3390/pathogens11060638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/12/2022] [Accepted: 05/19/2022] [Indexed: 02/04/2023] Open
Abstract
Malaria remains a major public health concern in Africa. Metabolic resistance in major malaria vectors such as An. funestus is jeopardizing the effectiveness of long-lasting insecticidal nets (LLINs) to control malaria. Here, we used experimental hut trials (EHTs) to investigate the impact of cytochrome P450-based resistance on the efficacy of PBO-based net (Olyset Plus) compared to a permethrin-only net (Olyset), revealing a greater loss of efficacy for the latter. EHT performed with progenies of F5 crossing between the An. funestus pyrethroid-resistant strain FUMOZ and the pyrethroid-susceptible strain FANG revealed that PBO-based nets (Olyset Plus) induced a significantly higher mortality rate (99.1%) than pyrethroid-only nets (Olyset) (56.7%) (p < 0.0001). The blood-feeding rate was higher in Olyset compared to Olyset Plus (11.6% vs. 5.6%; p = 0.013). Genotyping the CYP6P9a/b and the intergenic 6.5 kb structural variant (SV) resistance alleles showed that, for both nets, homozygote-resistant mosquitoes have a greater ability to blood-feed than the susceptible mosquitoes. Homozygote-resistant genotypes significantly survived more with Olyset after cone assays (e.g., CYP6P9a OR = 34.6; p < 0.0001) than homozygote-susceptible mosquitoes. A similar but lower correlation was seen with Olyset Plus (OR = 6.4; p < 0.001). Genotyping EHT samples confirmed that CYP6P9a/b and 6.5 kb_SV homozygote-resistant mosquitoes survive and blood-feed significantly better than homozygote-susceptible mosquitoes when exposed to Olyset. Our findings highlight the negative impact of P450-based resistance on pyrethroid-only nets, further supporting that PBO nets, such as Olyset Plus, are a better solution in areas of P450-mediated resistance to pyrethroids.
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Affiliation(s)
- Benjamin D. Menze
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK;
- Medical Entomology Department, Centre for Research in Infectious Diseases (CRID), Yaoundé 13591, Cameroon; (L.M.J.M.); (M.T.); (M.T.)
- Correspondence: (B.D.M.); (C.S.W.)
| | - Leon M. J. Mugenzi
- Medical Entomology Department, Centre for Research in Infectious Diseases (CRID), Yaoundé 13591, Cameroon; (L.M.J.M.); (M.T.); (M.T.)
| | - Magellan Tchouakui
- Medical Entomology Department, Centre for Research in Infectious Diseases (CRID), Yaoundé 13591, Cameroon; (L.M.J.M.); (M.T.); (M.T.)
| | - Murielle J. Wondji
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK;
- Medical Entomology Department, Centre for Research in Infectious Diseases (CRID), Yaoundé 13591, Cameroon; (L.M.J.M.); (M.T.); (M.T.)
| | - Micareme Tchoupo
- Medical Entomology Department, Centre for Research in Infectious Diseases (CRID), Yaoundé 13591, Cameroon; (L.M.J.M.); (M.T.); (M.T.)
| | - Charles S. Wondji
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK;
- Medical Entomology Department, Centre for Research in Infectious Diseases (CRID), Yaoundé 13591, Cameroon; (L.M.J.M.); (M.T.); (M.T.)
- Correspondence: (B.D.M.); (C.S.W.)
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An Experimental Hut Evaluation of PBO-Based and Pyrethroid-Only Nets against the Malaria Vector Anopheles funestus Reveals a Loss of Bed Nets Efficacy Associated with GSTe2 Metabolic Resistance. Genes (Basel) 2020; 11:genes11020143. [PMID: 32013227 PMCID: PMC7073577 DOI: 10.3390/genes11020143] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/14/2019] [Accepted: 12/16/2019] [Indexed: 11/16/2022] Open
Abstract
Growing insecticide resistance in malaria vectors is threatening the effectiveness of insecticide-based interventions, including Long Lasting Insecticidal Nets (LLINs). However, the impact of metabolic resistance on the effectiveness of these tools remains poorly characterized. Using experimental hut trials and genotyping of a glutathione S-transferase resistance marker (L119F-GSTe2), we established that GST-mediated resistance is reducing the efficacy of LLINs against Anopheles funestus. Hut trials performed in Cameroon revealed that Piperonyl butoxide (PBO)-based nets induced a significantly higher mortality against pyrethroid resistant An. funestus than pyrethroid-only nets. Blood feeding rate and deterrence were significantly higher in all LLINs than control. Genotyping the L119F-GSTe2 mutation revealed that, for permethrin-based nets, 119F-GSTe2 resistant mosquitoes have a greater ability to blood feed than susceptible while the opposite effect is observed for deltamethrin-based nets. For Olyset Plus, a significant association with exophily was observed in resistant mosquitoes (OR = 11.7; p < 0.01). Furthermore, GSTe2-resistant mosquitoes (cone assays) significantly survived with PermaNet 2.0 (OR = 2.1; p < 0.01) and PermaNet 3.0 (side) (OR = 30.1; p < 0.001) but not for Olyset Plus. This study shows that the efficacy of PBO-based nets (e.g., blood feeding inhibition) against pyrethroid resistant malaria vectors could be impacted by other mechanisms including GST-mediated metabolic resistance not affected by the synergistic action of PBO. Mosaic LLINs incorporating a GST inhibitor (diethyl maleate) could help improve their efficacy in areas of GST-mediated resistance.
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More S, Bøtner A, Butterworth A, Calistri P, Depner K, Edwards S, Garin‐Bastuji B, Good M, Gortázar Schmidt C, Michel V, Miranda MA, Nielsen SS, Raj M, Sihvonen L, Spoolder H, Stegeman JA, Thulke H, Velarde A, Willeberg P, Winckler C, Baldinelli F, Broglia A, Dhollander S, Beltrán‐Beck B, Kohnle L, Morgado J, Bicout D. Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): West Nile fever. EFSA J 2017; 15:e04955. [PMID: 32625621 PMCID: PMC7009844 DOI: 10.2903/j.efsa.2017.4955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
West Nile fever (WNF) has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of WNF to be listed, Article 9 for the categorisation of WNF according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to WNF. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, WNF can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 2 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (b) and (e) of Article 9(1). The animal species to be listed for WNF according to Article 8(3) criteria are several orders of birds and mammals as susceptible species and several families of birds as reservoir. Different mosquito species can serve as vectors.
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