Prevalence of onchocerciasis and epilepsy in a Tanzanian region after a prolonged community-directed treatment with ivermectin by Mushi, VP, Bhwana, D, Massawe, IS, Makunde, W, Sebukoto, H, Ngasa, W, Sengerema, J, Mhina, A, Hayuma, PM, Kimambo, H, Kidima, W, Matuja, W, Sander, JW, Cross, H, Sen, A, Colebunders, R, Newton, CR, Mmbando, BP, EPInA Study Group