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

Abstract

Baseline and impact assessment data were generated in 1994 (n = 532) and 2011 (n = 593) from 6 sentinel villages with generalized onchocerciasis. Only volunteers and a cohort (n = 445, 75%) 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, P < 0.05, (t-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 (R 2 = 0.898 − 0.949). Dissected parous Simulium damnosum caught (n = 222) 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.

Status of parasitological indicators and morbidity burden of onchocerciasis after years of successive implementation of mass distribution of ivermectin in selected communities of Yeki and Asosa districts, Ethiopia

“…We believe that the switch from annual to biannual CDTi in 2015 might have contributed to bringing the prevalence and intensity of infection status to zero level. Similar findings were reported from other endemic areas where at least 14 rounds of MDA was carried out in Africa [45,[49][50][51][52][53][54] and Latin America [55]. In contrast, irrespective of long term CDTi, considerably higher prevalences than the present finding were reported from other CDTi implementation areas in Africa [29,[56][57][58][59][60][61][62].…”

“…The biting rate is reported by residents to be intense especially near to the Dabus River. Relatively higher prevalence of infection than this was reported in other studies after similar years of intervention [43,49,[65][66][67][78][79][80][81][82][83].…”

“…This study showed that 15 years of continuous CDTi has brought the prevalence of infection to zero. The skin mf reservoir available to the local vector population in the area might have gradually decreased after the long term treatment [48], and ultimately with possible interruption of active parasite transmission [49]. We believe that the switch from annual to biannual CDTi in 2015 might have contributed to bringing the prevalence and intensity of infection status to zero level.…”

Relationship between oral declaration on adherence to ivermectin treatment and parasitological indicators of onchocerciasis in an area of persistent transmission despite a decade of mass drug administration in Cameroon

“…This could be attributed to the fact that ivermectin is a microfilaricidal drug and as such has minor effects on adult worms in nodules hence the little variations in nodule prevalence and intensity with treatment [ 21 , 61 , 62 ]. In the savannah areas, there are data both published and unpublished showing that nodule rate reduces with the IVM MDA [ 63 ]. The persistent nodule rate in this area, could also be explained by continuous transmission.…”

Prevalence of onchocerciasis after seven years of continuous community-directed treatment with ivermectin in the Ntui health district, Centre region, Cameroon

“…(26.3%) in the central region of Cameroon [ 14 ] or by Osue et al . (37.9%) in Nigeria [ 22 ]. The difference observed in these studies can be due to the fact that populations have more or less taken the annual Mectizan™ treatment.…”