Onchocerciasis status in Guinea-Bissau: An overview of trends in epidemiological and entomological indicators

The World Health Organization recommends monitoring infection and entomological indicators to evaluate onchocerciasis elimination. We reviewed trends in Guinea-Bissau since the onset of interventions to assess current progress toward elimination.

We collated programmatic, entomological, and epidemiological data from Guinea-Bissau, including Onchocerciasis Control Programme (OCP) records, impact data, and community-directed treatment with ivermectin (CDTi) data. Trends were visualized to assess impact.

Pre-control microfiladermia (mf) prevalences reached up to 70.6% along Rio Corubal and 27.4% along Rio Géba. Mf intensity ranged up to 59.9 and 6.5 mf/skin snip, respectively. Mf prevalence and intensity declined over time, despite irregular CDTi. In 2007-2008, the highest mf prevalence was 9.7% (Rio Corubal). Despite all villages being mf skin snip-negative by 2015, the detection of OV16 ELISA-positives (0.7%-14.9%) indicated ongoing transmission. Entomological surveys (2015) reported a blackfly infectivity rate of 0.06%, with infectious flies found at two of five sites (Gabú region).

CDTi substantially reduced mf prevalence, intensity, and vector infectivity in Guinea-Bissau, but transmission was not reduced to zero. Renewed serological and entomological assessments are needed to accurately determine elimination progress.