Modelling anti-Ov16 seroprevalence for the control and elimination of onchocerciasis
- Aditya Ramani
- Jacob N. Stapley
- Matthew A. Dixon
- Jonathan I. D. Hamley
- Luís-Jorge Amaral
- Maria-Gloria Basáñez
- Martin Walker
2026-08-19
The World Health Organization aims to verify elimination of onchocerciasis transmission in 12 endemic countries by 2030. Serological assays detecting IgG4 antibodies against the Onchocerca volvulus Ov16 antigen guide decision-making regarding start- and stop-mass ivermectin treatment, post-treatment and post-elimination surveillance. Transmission models are crucial for understanding anti-Ov16 IgG4 seroprevalence dynamics. Uncertainty associated with the parasite stage(s) stimulating seroconversion and duration of antibody persistence has hitherto hindered progress. We use the individual-based stochastic transmission model, EPIONCHO-IBM, to test hypotheses regarding the timing of seroconversion and seroreversion. We fit the model to data from (treatment-naïve) Gabon and validate it using data from Togo (four decades of control). The best-fit hypothesis is that seroconversion is elicited by near-patent/patent infection. The duration of antibody persistence remains uncertain. Our findings support the use of mechanistic transmission models to refine serological thresholds for start- and stop-treatment, and aid interpretation of post-treatment and post-elimination surveillance serological signals.