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Background <p>Onchocerciasis remains a major public health problem in sub-Saharan Africa, despite decades of control efforts. In Senegal, transmission was historically focal but intense along the Gambia and Falémé river basins in the southeast of the country. Building on the legacy of the Onchocerciasis Control Programme and the African Programme for Onchocerciasis Control, Senegal implemented long-term community-directed mass drug administration (MDA) with ivermectin, aiming to interrupt local transmission and progress towards elimination.</p> Methods <p>A retrospective descriptive analysis was conducted based on data from the Senegalese National Onchocerciasis Control Programme between 1998 and 2022. Annual MDA reports were used to estimate geographical and therapeutic coverage across endemic districts. Epidemiological impact was assessed through serial parasitological surveys (skin snips), entomological pool-screen PCR of Simulium blackflies, and Ov16 IgG4 ELISA performed on dried blood spots collected from children aged 5–9 years in the Gambia and Falémé river basins. These data were interpreted against WHO thresholds for stopping MDA and for verification of elimination.</p> Results <p>From 1998 onwards, geographical coverage rapidly reached 100% of identified endemic villages and was maintained throughout the programme. Therapeutic coverage remained around 78–80% of the total population annually, exceeding the WHO minimum target of 65%. Microfilarial prevalence fell from hyperendemic baseline levels (&gt; 15% with nodules in some villages) to near zero within a decade. In the most recent surveys (2020 and 2022), skin snip examinations of more than 1,100 individuals across four historically endemic districts detected no microfilariae. Entomological pool-screening of hundreds of thousands of Simulium flies showed infection rates generally below 0.2%, with several years at zero and values consistently under the WHO threshold for sustainable transmission. In 2022, none of the 6,229 children tested by Ov16 ELISA (3,077 from the Gambia basin and 3,150 from the Falémé basin) was seropositive (95% CI 0–0.06%), indicating the absence of recent exposure to <i>Onchocerca volvulus</i>.</p> Conclusion <p>High and sustained coverage with community-directed ivermectin MDA, combined with rigorous parasitological, entomological and serological surveillance, has led to the apparent interruption of <i>O. volvulus</i> transmission in Senegal’s historical foci. MDA was safely stopped nationwide in 2022, and the country has entered a three-year post-treatment surveillance phase in line with WHO guidelines. Maintaining integrated surveillance and cross-border collaboration will be essential to prevent recrudescence and to support Senegal’s dossier for WHO verification of onchocerciasis elimination.</p>

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Progress towards Onchocerciasis elimination in Senegal’s historical transmission zones, following sustained annual mass drug administration and multilevel surveillance

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月4日

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  • Djiby Sow,
  • Mamadou Alpha Diallo,
  • Rose Monteil,
  • Aita Sene,
  • Achille Kabore,
  • Moussa Dieng Sarr,
  • Khadim Diongue,
  • Mame Cheikh Seck,
  • Mouhamadou Ndiaye,
  • Aida Sadikh Badiane,
  • Mariama Touré,
  • Daniel Boakye,
  • Didier K. Bakajika,
  • Ngayo Sy,
  • Daouda Ndiaye

摘要

Background

Onchocerciasis remains a major public health problem in sub-Saharan Africa, despite decades of control efforts. In Senegal, transmission was historically focal but intense along the Gambia and Falémé river basins in the southeast of the country. Building on the legacy of the Onchocerciasis Control Programme and the African Programme for Onchocerciasis Control, Senegal implemented long-term community-directed mass drug administration (MDA) with ivermectin, aiming to interrupt local transmission and progress towards elimination.

Methods

A retrospective descriptive analysis was conducted based on data from the Senegalese National Onchocerciasis Control Programme between 1998 and 2022. Annual MDA reports were used to estimate geographical and therapeutic coverage across endemic districts. Epidemiological impact was assessed through serial parasitological surveys (skin snips), entomological pool-screen PCR of Simulium blackflies, and Ov16 IgG4 ELISA performed on dried blood spots collected from children aged 5–9 years in the Gambia and Falémé river basins. These data were interpreted against WHO thresholds for stopping MDA and for verification of elimination.

Results

From 1998 onwards, geographical coverage rapidly reached 100% of identified endemic villages and was maintained throughout the programme. Therapeutic coverage remained around 78–80% of the total population annually, exceeding the WHO minimum target of 65%. Microfilarial prevalence fell from hyperendemic baseline levels (> 15% with nodules in some villages) to near zero within a decade. In the most recent surveys (2020 and 2022), skin snip examinations of more than 1,100 individuals across four historically endemic districts detected no microfilariae. Entomological pool-screening of hundreds of thousands of Simulium flies showed infection rates generally below 0.2%, with several years at zero and values consistently under the WHO threshold for sustainable transmission. In 2022, none of the 6,229 children tested by Ov16 ELISA (3,077 from the Gambia basin and 3,150 from the Falémé basin) was seropositive (95% CI 0–0.06%), indicating the absence of recent exposure to Onchocerca volvulus.

Conclusion

High and sustained coverage with community-directed ivermectin MDA, combined with rigorous parasitological, entomological and serological surveillance, has led to the apparent interruption of O. volvulus transmission in Senegal’s historical foci. MDA was safely stopped nationwide in 2022, and the country has entered a three-year post-treatment surveillance phase in line with WHO guidelines. Maintaining integrated surveillance and cross-border collaboration will be essential to prevent recrudescence and to support Senegal’s dossier for WHO verification of onchocerciasis elimination.