Progress towards onchocerciasis elimination in Côte d'Ivoire: A geospatial modelling study.

Area of Science:

• Tropical medicine
• Infectious disease epidemiology
• Public health interventions

Background:

• Côte d'Ivoire has implemented 45 years of onchocerciasis control, including vector control, mass drug administration (MDA), and community-directed treatment with ivermectin (CDTi).
• Modeling endemicity during different intervention phases helps assess progress toward disease elimination.

Purpose of the Study:

• To model onchocerciasis endemicity in Côte d'Ivoire using historical data.
• To identify areas at risk for ongoing transmission and inform future control strategies.

Main Methods:

• Utilized Ministry of Health skin snip microfilaria (MF) prevalence and intensity data (1975-2016).
• Incorporated socio-demographic and environmental factors into a machine learning algorithm to map endemicity.
• Assessed model performance using root mean squared error and R2 values.

Main Results:

• Predicted mean MF prevalence dropped from 51.8% (circa 1991) to 3.9% (circa 2016).
• Predicted mean community MF load (CMFL) decreased from 10.1 MF/snip to 0.1 MF/snip.
• Higher infection prevalence and density foci were predicted in the southern region; proximity to water and altitude were key correlates.

Conclusions:

• Widespread ivermectin use has significantly reduced onchocerciasis in Côte d'Ivoire.
• Predictive maps highlight areas requiring continued surveillance for potential ongoing transmission.
• Sustained CDTi, active surveillance, and monitoring are crucial for future onchocerciasis elimination.