Impact of Eighteen-Year Varied Compliance to Onchocerciasis Treatment with Ivermectin in Sentinel Savannah Agrarian Communities in Kaduna State of Nigeria

Baseline and impact assessment data were generated in 1994 ( ) and 2011 ( ) from 6 sentinel villages with generalized onchocerciasis. Only volunteers and a cohort were screened at both visits. Each village had received 11 (64.7%) annual treatments and 92.6%, range 88.7–100%, treatment compliance. Overall mean number of treatment was 2.9 ± 1.6 with a range 2.0 ± 1.2–3.3 ± 0.6. Significant decreases in skin microfilaria prevalence from 201 (38%) to 0 (0%), palpable nodule from 77 (15%) to 4 (0.7%), dermal changes from 51 (9.6%) to 2 (0.04%), optic nerve disease from 24 (4.5%) to 4 (2.0%), and onchocercal inducible ocular lesions from 31 (5.8%) to 12 (2.0%) were recorded, , ( -test of unpaired data). Cases of glaucoma, 8 (1.4%), and blindness, 6 (1.05%), remained unchanged. Visual acuity ≥6/24 in one or both eyes, 198 (33.45%); cataract, 169 (28.5%); pterygium 157 (26.5%); and acute senilis, 165 (27.9%), were significantly increased and positively correlated with increase in age ( ). Dissected parous Simulium damnosum caught ( ) were without infective third stage larva. Active onchocerciasis transmission seems halted despite varied compliance to long-term ivermectin treatment. We recommend continued surveillance and targeted treatment of controlled and hypoendemic areas. 1. Introduction Onchocerciasis is a debilitating disease affecting the skin and eye leading to visual impairment and blindness. It is caused by a filarial nematode worm (Onchocerca volvulus) transmitted from person to person by the bite of black flies, Simulium species. Since the vector breeds in fast flowing rivers and those within the area are exposed to the disease, it is called “river blindness.” It is ranked among the four major preventable causes of blindness in the world, after trachoma, cataract, and glaucoma [1] and the leading cause of blindness in sub-Saharan Africa. Over 20 million people are projected to be infected, 1 million are blind and 70 million at risk of infection worldwide [2]. Nigeria accounts for one third of these estimates. The disease is found in all States of Nigeria with varying degrees of endemicity and severity of clinical manifestations [3–5] Both the savannah type that is associated with severe eye disorders and blindness and the forest type which causes more skin damage are present and responsible for the divergent clinicoepidemiologic picture. One of the major reasons the north of Nigeria is reported to have higher blindness rates than the southern part is owing to the widespread distribution of savannah species of O. volvulus. In the south the forest