Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia
Abstract Background Pyrethroid-based indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) have been employed as key vector control measures against malaria in Namibia. However, pyrethroid resistance in Anopheles mosquitoes may compromise the efficacy of these interventions. To a...
| Main Authors: | , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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BMC
2024-03-01
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| Series: | Malaria Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s12936-024-04898-y |
| _version_ | 1797259525079695360 |
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| author | Rosalia N. Joseph Tabeth Mwema Seth J. Eiseb Deodatus V. Maliti Munyaradzi Tambo Iitula Iitula Lydia Eloff Ophilia Lukubwe Cara Smith-Gueye Élodie A. Vajda Allison Tatarsky Stark T. Katokele Petrina N. Uusiku Dennis Walusimbi Sheila B. Ogoma Davis R. Mumbengegwi Neil F. Lobo |
| author_facet | Rosalia N. Joseph Tabeth Mwema Seth J. Eiseb Deodatus V. Maliti Munyaradzi Tambo Iitula Iitula Lydia Eloff Ophilia Lukubwe Cara Smith-Gueye Élodie A. Vajda Allison Tatarsky Stark T. Katokele Petrina N. Uusiku Dennis Walusimbi Sheila B. Ogoma Davis R. Mumbengegwi Neil F. Lobo |
| author_sort | Rosalia N. Joseph |
| collection | DOAJ |
| description | Abstract Background Pyrethroid-based indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) have been employed as key vector control measures against malaria in Namibia. However, pyrethroid resistance in Anopheles mosquitoes may compromise the efficacy of these interventions. To address this challenge, the World Health Organization (WHO) recommends the use of piperonyl butoxide (PBO) LLINs in areas where pyrethroid resistance is confirmed to be mediated by mixed function oxidase (MFO). Methods This study assessed the susceptibility of Anopheles gambiae sensu lato (s.l.) mosquitoes to WHO tube bioassays with 4% DDT and 0.05% deltamethrin insecticides. Additionally, the study explored the effect of piperonyl butoxide (PBO) synergist by sequentially exposing mosquitoes to deltamethrin (0.05%) alone, PBO (4%) + deltamethrin (0.05%), and PBO alone. The Anopheles mosquitoes were further identified morphologically and molecularly. Results The findings revealed that An. gambiae sensu stricto (s.s.) (62%) was more prevalent than Anopheles arabiensis (38%). The WHO tube bioassays confirmed resistance to deltamethrin 0.05% in the Oshikoto, Kunene, and Kavango West regions, with mortality rates of 79, 86, and 67%, respectively. In contrast, An. arabiensis displayed resistance to deltamethrin 0.05% in Oshikoto (82% mortality) and reduced susceptibility in Kavango West (96% mortality). Notably, there was reduced susceptibility to DDT 4% in both An. gambiae s.s. and An. arabiensis from the Kavango West region. Subsequently, a subsample from PBO synergist assays in 2020 demonstrated a high proportion of An. arabiensis in Oshana (84.4%) and Oshikoto (73.6%), and 0.42% of Anopheles quadriannulatus in Oshana. Non-amplifiers were also present (15.2% in Oshana; 26.4% in Oshikoto). Deltamethrin resistance with less than 95% mortality, was consistently observed in An. gambiae s.l. populations across all sites in both 2020 and 2021. Following pre-exposure to the PBO synergist, susceptibility to deltamethrin was fully restored with 100.0% mortality at all sites in 2020 and 2021. Conclusions Pyrethroid resistance has been identified in An. gambiae s.s. and An. arabiensis in the Kavango West, Kunene, and Oshikoto regions, indicating potential challenges for pyrethroid-based IRS and LLINs. Consequently, the data highlights the promise of pyrethroid-PBO LLINs in addressing resistance issues in the region. |
| first_indexed | 2024-04-24T23:10:48Z |
| format | Article |
| id | doaj.art-bd170a89508548969010d0994a710940 |
| institution | Directory Open Access Journal |
| issn | 1475-2875 |
| language | English |
| last_indexed | 2024-04-24T23:10:48Z |
| publishDate | 2024-03-01 |
| publisher | BMC |
| record_format | Article |
| series | Malaria Journal |
| spelling | doaj.art-bd170a89508548969010d0994a7109402024-03-17T12:16:05ZengBMCMalaria Journal1475-28752024-03-012311910.1186/s12936-024-04898-yInsecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern NamibiaRosalia N. Joseph0Tabeth Mwema1Seth J. Eiseb2Deodatus V. Maliti3Munyaradzi Tambo4Iitula Iitula5Lydia Eloff6Ophilia Lukubwe7Cara Smith-Gueye8Élodie A. Vajda9Allison Tatarsky10Stark T. Katokele11Petrina N. Uusiku12Dennis Walusimbi13Sheila B. Ogoma14Davis R. Mumbengegwi15Neil F. Lobo16University of Namibia (UNAM)University of Namibia (UNAM)University of Namibia (UNAM)Clinton Health Access Initiative (CHAI)University of Namibia (UNAM)Ministry of Health and Social Services (MoHSS)University of Namibia (UNAM)Clinton Health Access Initiative (CHAI)Malaria Elimination Initiative, University of California, san franciscoMalaria Elimination Initiative, University of California, san franciscoMalaria Elimination Initiative, University of California, san franciscoMinistry of Health and Social Services (MoHSS)Ministry of Health and Social Services (MoHSS)Clinton Health Access Initiative (CHAI)Clinton Health Access Initiative (CHAI)University of Namibia (UNAM)Malaria Elimination Initiative, University of California, san franciscoAbstract Background Pyrethroid-based indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) have been employed as key vector control measures against malaria in Namibia. However, pyrethroid resistance in Anopheles mosquitoes may compromise the efficacy of these interventions. To address this challenge, the World Health Organization (WHO) recommends the use of piperonyl butoxide (PBO) LLINs in areas where pyrethroid resistance is confirmed to be mediated by mixed function oxidase (MFO). Methods This study assessed the susceptibility of Anopheles gambiae sensu lato (s.l.) mosquitoes to WHO tube bioassays with 4% DDT and 0.05% deltamethrin insecticides. Additionally, the study explored the effect of piperonyl butoxide (PBO) synergist by sequentially exposing mosquitoes to deltamethrin (0.05%) alone, PBO (4%) + deltamethrin (0.05%), and PBO alone. The Anopheles mosquitoes were further identified morphologically and molecularly. Results The findings revealed that An. gambiae sensu stricto (s.s.) (62%) was more prevalent than Anopheles arabiensis (38%). The WHO tube bioassays confirmed resistance to deltamethrin 0.05% in the Oshikoto, Kunene, and Kavango West regions, with mortality rates of 79, 86, and 67%, respectively. In contrast, An. arabiensis displayed resistance to deltamethrin 0.05% in Oshikoto (82% mortality) and reduced susceptibility in Kavango West (96% mortality). Notably, there was reduced susceptibility to DDT 4% in both An. gambiae s.s. and An. arabiensis from the Kavango West region. Subsequently, a subsample from PBO synergist assays in 2020 demonstrated a high proportion of An. arabiensis in Oshana (84.4%) and Oshikoto (73.6%), and 0.42% of Anopheles quadriannulatus in Oshana. Non-amplifiers were also present (15.2% in Oshana; 26.4% in Oshikoto). Deltamethrin resistance with less than 95% mortality, was consistently observed in An. gambiae s.l. populations across all sites in both 2020 and 2021. Following pre-exposure to the PBO synergist, susceptibility to deltamethrin was fully restored with 100.0% mortality at all sites in 2020 and 2021. Conclusions Pyrethroid resistance has been identified in An. gambiae s.s. and An. arabiensis in the Kavango West, Kunene, and Oshikoto regions, indicating potential challenges for pyrethroid-based IRS and LLINs. Consequently, the data highlights the promise of pyrethroid-PBO LLINs in addressing resistance issues in the region.https://doi.org/10.1186/s12936-024-04898-yAnopheles gambiae sensu latoInsecticide resistancePyrethroidPBO synergist |
| spellingShingle | Rosalia N. Joseph Tabeth Mwema Seth J. Eiseb Deodatus V. Maliti Munyaradzi Tambo Iitula Iitula Lydia Eloff Ophilia Lukubwe Cara Smith-Gueye Élodie A. Vajda Allison Tatarsky Stark T. Katokele Petrina N. Uusiku Dennis Walusimbi Sheila B. Ogoma Davis R. Mumbengegwi Neil F. Lobo Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia Malaria Journal Anopheles gambiae sensu lato Insecticide resistance Pyrethroid PBO synergist |
| title | Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia |
| title_full | Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia |
| title_fullStr | Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia |
| title_full_unstemmed | Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia |
| title_short | Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia |
| title_sort | insecticide susceptibility status of anopheles gambiae mosquitoes and the effect of pre exposure to a piperonyl butoxide pbo synergist on resistance to deltamethrin in northern namibia |
| topic | Anopheles gambiae sensu lato Insecticide resistance Pyrethroid PBO synergist |
| url | https://doi.org/10.1186/s12936-024-04898-y |
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