Impact assessment study after 27 years of community-directed treatment with ivermectin in Galadimawa, Kaduna State, Nigeria.

Purpose: To assess the impact on blindness after 27 years of community-directed treatment with ivermectin (CDTI) in the Galadimawa community of Kauru Local Government in Kaduna state, Nigeria. The population of Galadimawa constituted about 12% of the total population examined during the ivermectin randomised control trial (RCT) in 1989. The RCT population of 8000 individuals was scattered over 36 villages in Kaduna state. Thus, longitudinal data are available on blindness.

Materials And Methods: After 27 years of dosing with ivermectin, the people in the community of Galadimawa were re-examined for the prevalence and causes of blindness. This was achieved by an examination of the visually disabled. The findings were compared with the situation in 1989 before the dosing commenced.

Results: The population of the village increased from 711 to 1419. The prevalence of blindness dropped from 4.9 to 0.96%. The most common causes of blindness were now cataract (55.2%) and optic atrophy (27.6%), whereas the most common causes in 1989 were onchocerciasis (28.3%), glaucoma (17.4%) and cataract (10.9%). People with optic atrophy were more likely to have taken fewer doses of ivermectin over the years. The blind people encountered in 2016 were on average 17 years older than those seen in 1989, which suggests that blindness, when it occurs, is delayed by almost two decades.

Conclusion: CDTI has reduced the prevalence of blindness significantly in Galadimawa and may reflect the situation elsewhere in the Kaduna state, which is an oncho-endemic zone.