Parasites & Vectors (Jan 2024)

The impact of pyrethroid-pyriproxyfen and pyrethroid-chlorfenapyr long-lasting insecticidal nets on density of primary malaria vectors Anopheles gambiae s.s. and Anopheles coluzzii in Benin: a secondary analysis of a cluster randomised controlled trial

  • Boulais Yovogan,
  • Arthur Sovi,
  • Armel Djènontin,
  • Constantin J. Adoha,
  • Bruno Akinro,
  • Manfred Accrombessi,
  • Edouard Dangbénon,
  • Come Z. Koukpo,
  • Zul-Kifl Affolabi,
  • Prudenciène A. Agboho,
  • Casimir Dossou Kpanou,
  • Landry Assongba,
  • Antoine Abel Missihoun,
  • Tatchémè Filémon Tokponnon,
  • Clément Agbangla,
  • Germain Gil Padonou,
  • Louisa A. Messenger,
  • Corine Ngufor,
  • Jackie Cook,
  • Martin C. Akogbéto,
  • Natacha Protopopoff

DOI
https://doi.org/10.1186/s13071-023-06104-5
Journal volume & issue
Vol. 17, no. 1
pp. 1 – 12

Abstract

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Abstract Background Long-lasting insecticidal nets (LLINs) may have different impacts on distinct mosquito vector species. We assessed the efficacy of pyrethroid-pyriproxyfen and pyrethroid-chlorfenapyr LLINs on the density of Anopheles gambiae s.s. and An. coluzzii compared to pyrethroid-only nets in a three-arm cluster randomised control trial in Benin. Methods Indoor and outdoor collections of adult mosquitoes took place in 60 clusters using human landing catches at baseline and every 3 months for 2 years. After morphological identification, around 15% of randomly selected samples of An. gambiae s.l. were dissected to determine parity, species (using PCR). Results Overall, a total of 46,613 mosquito specimens were collected at baseline and 259,250 in the eight quarterly collections post-net distribution. Post-net distribution, approximately 70% of the specimens of An. gambiae s.l. speciated were An. coluzzii, while the rest were mostly composed of An. gambiae s.s. with a small proportion (< 1%) of hybrids (An. gambiae/coluzzii). There was no evidence of a significant reduction in vector density indoors in either primary vector species [An. coluzzii: DR (density ratio) = 0.62 (95% CI 0.21–1.77), p = 0.3683 for the pyrethroid-pyriproxyfen LLIN and DR = 0.56 (95% CI 0.19–1.62), p = 0.2866 for the pyrethroid-chlorfenapyr LLIN, An. gambiae s.s.: DR = 0.52 (95% CI 0.18–1.46), p = 0.2192 for the pyrethroid-pyriproxyfen LLIN and DR = 0.53 (95% CI 0.19–1.46), p = 0.2222 for the pyrethroid-chlorfenapyr]. The same trend was observed outdoors. Parity rates of An. gambiae s.l. were also similar across study arms. Conclusions Compared with pyrethroid-only LLINs, pyrethroid-chlorfenapyr LLINs and pyrethroid-pyriproxyfen LLINs performed similarly against the two primary mosquito species An. gambiae s.s. and An. coluzzii in Benin. Graphical Abstract

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