1. Sightsavers , 35 Perrymount Road, Haywards Heath, West Sussex RH16 3BZ, UK
2. Sightsavers , 1 Golf Course Road, P.O. Box 503, Kaduna, Nigeria
3. Benue State Neglected Tropical Disease Programme, Benue State Ministry of Health and Human Services , PMB 102093, Makurdi, Benue State, Nigeria
4. SCI Foundation , Edinburgh House, London, SE11 5DP, UK
5. School of Public Health, Imperial College London, Norfolk Place , London W2 1PG, UK