Serological Evaluation of Onchocerciasis and Lymphatic Filariasis Elimination in the Bakoye and Faleme Foci, Mali

Background. Ivermectin-based onchocerciasis elimination, reported in 2009-2012, for Bakoye and Faleme, Mali, supported policy-shifting from morbidity control to elimination of transmission (EOT). These foci are coendemic with lymphatic filariasis (LF). In 2007-2016 mass ivermectin plus albendazole administration was implemented. We report Ov16 (onchocerciasis) and Wb123 (LF) seroprevalence after 24-25 years of treatment to determine if onchocerciasis EOT and LF elimination as a public health problem (EPHP) have been achieved. Methods. The SD Bioline Onchocerciasis/LF Ig[immunoglobulin]G4 biplex rapid diagnostic test (RDT) was used in 2186 children aged 3-10 years in 13 villages (plus 2 hamlets) in Bakoye and in 2270 children in 15 villages (plus 1 hamlet) in Faleme. In Bakoye, all-age serosurveys were conducted in 3 historically hyperendemic villages (1867 individuals aged 3 -78 years). Results. In Bakoye, IgG4 seropositivity was 0.27% (95% confidence interval [CI] = .13%-.60%) for both Ov16 and Wb123 antigens. In Faleme, Ov16 and Wb123 seroprevalence was 0.04% (95% CI = .01%-.25%) and 0.09% (95% CI = .02%-.32%), respectively. Ov16-seropositive children were from historically meso/hyperendemic villages. Ov16 positivity was <2% in <= 14 year-olds, and 16% in >= 40 year-olds. Wb123 seropositivity was <2% in <= 39 year-olds, reaching 3% in >= 40 year-olds. Conclusions. Notwithstanding uncertainty in the biplex RDT sensitivity, Ov16 and Wb123 seroprevalence among children in Bakoye and Faleme is consistent with EOT (onchocerciasis) and EPHP (LF) since stopping treatment in 2016. The few Ov16-seropositive children should be skin-snip polymerase chain reaction tested and followed up.

Automated summary

The seroprevalence of Ov16 and Wb123 among children in Bakoye and Faleme is consistent with achieving the goals of onchocerciasis elimination and LF elimination as a public health problem after 24-25 years of treatment. Testing and follow-up are suggested for the few Ov16-seropositive children.