The onchocerciasis transmission models EPIONCHO and ONCHOSIM have been independently developed
and used to explore the feasibility of eliminating onchocerciasis from Africa with mass (annual or
biannual) distribution of ivermectin within the timeframes proposed by the World Health Organization
(WHO) and endorsed by the 2012 London Declaration on Neglected Tropical Diseases (i.e. by 2020/2025).
Based on the findings of our previous model comparison, we implemented technical refinements and
tested the projections of EPIONCHO and ONCHOSIM against long-term epidemiological data from two
West African transmission foci in Mali and Senegal where the observed prevalence of infection was
brought to zero circa 2007–2009 after 15–17 years of mass ivermectin treatment. We simulated these
interventions using programmatic information on the frequency and coverage of mass treatments and
trained the model projections using longitudinal parasitological data from 27 communities, evaluating
the projected outcome of elimination (local parasite extinction) or resurgence. We found that EPIONCHO
and ONCHOSIM captured adequately the epidemiological trends during mass treatment but that resurgence,
while never predicted by ONCHOSIM, was predicted by EPIONCHO in some communities with the
highest (inferred) vector biting rates and associated pre-intervention endemicities. Resurgence can be
extremely protracted such that low (microfilarial) prevalence between 1% and 5% can be maintained for
3–5 years before manifesting more prominently. We highlight that post-treatment and post-elimination
surveillance protocols must be implemented for long enough and with high enough sensitivity to detect
possible residual latent infections potentially indicative of resurgence. We also discuss uncertainty and
differences between EPIONCHO and ONCHOSIM projections, the potential importance of vector control
in high-transmission settings as a complementary intervention strategy, and the short remaining timeline
for African countries to be ready to stop treatment safely and begin surveillance in order to meet the
impending 2020/2025 elimination targets.