Onchocerciasis: the clinical and epidemiological burden of skin disease in Africa.

An attempt was made to assess the true public-health importance of onchocercal skin disease throughout the African region and hence provide an objective basis for the rational planning of onchocerciasis control in the area. The seven collaborative centres that participated in the study (three in Nigeria and one each in Ghana, Cameroon, Tanzania and Uganda) were all in areas of rainforest or savannah-forest mosaic where onchocercal blindness is not common. A cross-sectional dermatological survey was undertaken at each site following a standard protocol. At each site, the aim was to examine at least 750 individuals aged 5 years and living in highly endemic communities and 220-250 individuals aged 5 years and living in a hypo-endemic (control) community. Overall, there were 5459 and 1451 subjects from hyper-and hypo-endemic communities, respectively. In the highly endemic communities, the prevalence of itching increased with age until 20 years and then plateaued, affecting 42% of the population aged 20 years. There was a strong correlation between the prevalence of itching and the level of endemicity (as measured by the prevalence of nodules; r=0.75; P<0.001). The results of a multivariate logistic regression analysis showed that, at the individual level, the presence of onchocercal reactive skin lesions (acute papular onchodermatitis, chronic papular onchodermatitis and/or lichenified onchodermatitis) was the most important risk factor for pruritus, with an odds ratio (OR) of 18.3 and 95% confidence interval (CI) of 15.19-22.04, followed by the presence of palpable onchocercal nodules (OR=4.63; CI=4.05-5.29). In contrast, non-onchocercal skin disease contributed very little to pruritus in the study communities (OR=1.29; CI=1.1-1.51). Onchocercal skin lesions affected 28% of the population in the endemic villages. The commonest type was chronic papular onchodermatitis (13%), followed by depigmentation (10%) and acute papular onchodermatitis (7%). The highest correlation with endemicity was seen for the prevalence of any onchocercal skin lesion and/or pruritus combined (r=0.8; P<0.001). Cutaneous onchocerciasis was found to be a common problem in many endemic areas in Africa which do not have high levels of onchocercal blindness. These findings, together with recent observations that onchocercal skin disease can have major, adverse, psycho-social and socio-economic effects, justify the inclusion of regions with onchocercal skin disease in control programmes based on ivermectin distribution. On the basis of these findings, the World Health Organization launched a control programme for onchocerciasis, the African Programme for Onchocerciasis Control (APOC), that covers 17 endemic countries in Africa.

A multi-centre study of the effect of Mectizan treatment on onchocercal skin disease: clinical findings.

A multi-centre, double-blind, placebo-controlled trial of the effect of Mectizan (ivermectin, MSD) treatment on the skin disease and severe itching associated with onchocerciasis was carried out in the forest zones of Nigeria, Ghana and Uganda. Overall, 4072 subjects, none of whom had received Mectizan previously, were enrolled and allocated into four groups, to receive Mectizan every 3, 6 or 12 months or placebo every 3 months. Subjects with skin lesions were stratified within each treatment group to ensure equal representation. Each subject was given a clinical examination and interviewed on enrolment and then 3-monthly for 15 months. The presence and severity of itching were determined by open-ended questions followed by probing questions. Skin lesions were classified and their severity graded using a standard system. Analysis of the results was restricted to the data from the 1530 subjects who received all their scheduled treatments and attended all the follow-up visits. From 6 months onwards, all subjects who had received Mectizan reported less severe itching, had lower prevalences of reactive skin lesions and had less severe skin lesions than those in the placebo group (P < 0.05 for each). The greatest reductions, in both itching and skin disease, were seen in subjects treated with Mectizan every 6 months. Mectizan treatment is therefore beneficial for the control of troublesome itching and for reducing the prevalence and severity of skin disease causes by Onchocerca. it is recommended that mass distribution of Mectizan to communities in the study areas be carried out at 6-monthly intervals for maximum efficacy.

The effects of ivermectin on onchocercal skin disease and severe itching: results of a multicentre trial.

OBJECTIVE: To determine the effects of ivermectin in annual, 3-monthly and 6-monthly doses on onchocercal skin p6isease (OSD) and severe itching. METHOD: A multicentre, double-blind placebo controlled trial was conducted among 4072 residents of rural communities in Ghana, Nigeria and Uganda. Baseline clinical examination categorized reactive skin lesions as acute papular onchodermatitis, chronic papular onchodermatitis and lichenified onchodermatitis. Presence and severity of itching was determined by open-ended and probing questions. Clinical examination and interview took place at baseline and each of 5 subsequent 3-monthly follow-up visits. RESULTS: While prevalence and severity of reactive lesions decreased for all 4 arms, those receiving ivermectin maintained a greater decrease in prevalence and severity over time. The difference between ivermectin and placebo groups was significant for prevalence at 9 months and for severity at 3 months. Differences between placebo and ivermectin groups were much more pronounced for itching. From 6 months onward, the prevalence of severe itching was reduced by 40-50% among those receiving ivermectin compared to the trend in the placebo group. CONCLUSION: This is an important effect on disease burden as severe itching is for the affected people the most troubling complication of onchocerciasis. The difference among regimens was not significant, and the recommended regimen of annual treatment for the control of ocular onchocerciasis appears also the most appropriate for onchocerciasis control in areas where the skin manifestations predominate. The final determination of the effect on skin lesions requires a longer period of study.