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Peer-reviewedCC BY-NC-ND 4.0Malaria Journal

Durability of Yorkool® long-lasting insecticidal nets in Benin: temporal evolution of deltamethrin concentration assessed using portable C-Vue HPLC chromatography during household use

  • Steve Zinsou Hougbe1
  • Razaki A. Ossé1,2,3
  • Minassou Juvenal Ahouandjinou1,2,3
  • Koffi Djigbodi Koumodji1
  • Zul-kifl Affolabi1,2,3
  • Arthur Sovi4
  • Sena V. Alohoutade1
  • Idelphonse Ahogni1
  • Terry Layne5
  • Martin Akogbeto1
5 affiliations
  1. 1Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
  2. 2Laboratoire des Sciences Animales et Halieutiques, Unité de Recherche en Santé Animale et Biosécurité, Université Nationale d’Agriculture, Kétou, Bénin
  3. 3École de Gestion et d’Exploitation des Systèmes d’Elevage, Université Nationale d’Agriculture, Kétou, Benin
  4. 4Faculty of Agronomy, University of Parakou, Parakou, Benin
  5. 5Direction Cvue-HPLC, Atlanta, GA USA
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Abstract

Background: The effectiveness of long-lasting insecticidal nets (LLINs) depends on both chemical durability and sustained biological efficacy under operational conditions. However, insecticide depletion over time does not always correspond directly to loss of entomological effectiveness. This study assessed the relationship between deltamethrin content and biological efficacy of Yorkool® LLINs over 18 months of household use in Benin.

Methods: A longitudinal study was conducted in southern Benin to monitor Yorkool® LLINs at baseline (T0), 7 months (T7), 12 months (T12), and 18 months (T18). Household practice data were collected and analyzed at all time points except T0. However, chemical and biological evaluations were performed only at T0, T12, and T18. Deltamethrin surface concentrations were quantified using a portable C-Vue HPLC device and expressed in mg/m2. Biological efficacy was assessed using WHO cone bioassays with susceptible Anopheles gambiae Kisumu mosquitoes, measuring knock-down at 60 min and mortality at 24 h. Chemical and biological trends were analyzed comparatively.

Results: Mean deltamethrin concentration declined progressively from approximately 55 mg/m2 at T0 to 50.7 mg/m2 at T12 and 45.3 mg/m2 at T18. Despite this chemical depletion, cone bioassays showed consistently high knock-down and mortality rates, with most nets meeting WHO criteria for optimal or minimal effectiveness. The relationship between insecticide concentration and mosquito mortality was positive but non-linear, suggesting a biological threshold effect.

Conclusion: Yorkool® LLINs maintained high biological efficacy during the first 18 months of use despite moderate chemical depletion. These findings suggest that loss of insecticide content does not immediately translate into loss of functional performance. However, the absence of follow-up up to 36 months and the use of a susceptible mosquito strain limit extrapolation to full operational lifespan and resistance settings. Extended durability studies are needed to define the functional failure threshold of LLINs.

Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s12936-026-06103-8.

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Cite

BibTeXRIS
BibTeX
@article{hougbe2026durability,
  title = {{Durability of Yorkool® long-lasting insecticidal nets in Benin: temporal evolution of deltamethrin concentration assessed using portable C-Vue HPLC chromatography during household use}},
  author = {Steve Zinsou Hougbe and Razaki A. Ossé and Minassou Juvenal Ahouandjinou and Koffi Djigbodi Koumodji and Zul-kifl Affolabi and Arthur Sovi and Sena V. Alohoutade and Idelphonse Ahogni and Terry Layne and Martin Akogbeto},
  journal = {Malaria Journal},
  year = {2026},
  month = aug,
  doi = {10.1186/s12936-026-06103-8},
  url = {https://doi.org/10.1186/s12936-026-06103-8},
  note = {CC BY-NC-ND 4.0},
}
RIS
TY  - JOUR
TI  - Durability of Yorkool® long-lasting insecticidal nets in Benin: temporal evolution of deltamethrin concentration assessed using portable C-Vue HPLC chromatography during household use
AU  - Steve Zinsou Hougbe
AU  - Razaki A. Ossé
AU  - Minassou Juvenal Ahouandjinou
AU  - Koffi Djigbodi Koumodji
AU  - Zul-kifl Affolabi
AU  - Arthur Sovi
AU  - Sena V. Alohoutade
AU  - Idelphonse Ahogni
AU  - Terry Layne
AU  - Martin Akogbeto
PY  - 2026
DA  - 2026/08/12
JO  - Malaria Journal
DO  - 10.1186/s12936-026-06103-8
UR  - https://doi.org/10.1186/s12936-026-06103-8
AB  - Background: The effectiveness of long-lasting insecticidal nets (LLINs) depends on both chemical durability and sustained biological efficacy under operational conditions. However, insecticide depletion over time does not always correspond directly to loss of entomological effectiveness. This study assessed the relationship between deltamethrin content and biological efficacy of Yorkool® LLINs over 18 months of household use in Benin.  Methods: A longitudinal study was conducted in southern Benin to monitor Yorkool® LLINs at baseline (T0), 7 months (T7), 12 months (T12), and 18 months (T18). Household practice data were collected and analyzed at all time points except T0. However, chemical and biological evaluations were performed only at T0, T12, and T18. Deltamethrin surface concentrations were quantified using a portable C-Vue HPLC device and expressed in mg/m2. Biological efficacy was assessed using WHO cone bioassays with susceptible Anopheles gambiae Kisumu mosquitoes, measuring knock-down at 60 min and mortality at 24 h. Chemical and biological trends were analyzed comparatively.  Results: Mean deltamethrin concentration declined progressively from approximately 55 mg/m2 at T0 to 50.7 mg/m2 at T12 and 45.3 mg/m2 at T18. Despite this chemical depletion, cone bioassays showed consistently high knock-down and mortality rates, with most nets meeting WHO criteria for optimal or minimal effectiveness. The relationship between insecticide concentration and mosquito mortality was positive but non-linear, suggesting a biological threshold effect.  Conclusion: Yorkool® LLINs maintained high biological efficacy during the first 18 months of use despite moderate chemical depletion. These findings suggest that loss of insecticide content does not immediately translate into loss of functional performance. However, the absence of follow-up up to 36 months and the use of a susceptible mosquito strain limit extrapolation to full operational lifespan and resistance settings. Extended durability studies are needed to define the functional failure threshold of LLINs.  Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s12936-026-06103-8.
SN  - 1475-2875
ER  -