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The prevalence of enterobiasis and its relationship with anal itching and enuresis were investigated among 799, randomly selected children aged 5-14 years, who lived, either in an area of high population density or one with a much lower population density, in Calabar, Nigeria. The eggs of Enterobius vermicularis were found in anal swabs (collected with transparent adhesive tape) from 60 (7.5%) of the subjects tested, with the prevalence of infection appearing markedly higher in the 403 children from the area with a high population density than in the 396 from the less densely populated area (11.7% v. 3.3%; P < 0.05). Questionnaire-based interviews were used to determine which of the children suffered from anal itching, enuresis or both. Compared with the egg-negative subjects, the 60 children who were egg-positive for Enterobius were found to be much more likely to be suffering from anal itching (78.3% v. 28.3%; P < 0.05) or enuresis (53.3% v. 36.4%; P < 0.05). Enterobiasis is therefore not a problem that is restricted to the temperate regions of the world, and may be a cause of enuresis or at least a contributory factor in the development of this complaint.

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.

To assess the impact of 5 years of annual community treatment with ivermectin (Mectizan) on the prevalence of onchocerciasis and onchocerciasis-associated morbidity, data collected, before and after such treatment, in the village of Gami, in a hyper-endemic area of the Central African Republic, were analysed. Skin snips from all the villagers treated in 1990 and/or 1995 were used to assess the prevalence and intensity of infection with Onchocerca volvulus. Ocular and dermatological morbidity was assessed by ophthalmological and clinical examinations of the same subjects. Following the five annual treatments, there was a reduction in the prevalence of infection and a dramatic decrease in the microfilarial load of the community. The prevalences of pruritus, onchocercal nodules and impaired vision were all significantly reduced. The results emphasise the long-term benefits of the mass-treatment programmes, particularly for children aged <10 years.

A clinical and parasitological assessment of onchodermatitis was conducted in a rural area of Morogoro district, Tanzania. The study population consisted of 1,005 individuals aged > or = 5 years: 749 from a hyper-endemic community and 256 from a hypo-endemic. The prevalence of troublesome itching was 67.0% in the hyper-endemic community but only 5% (13/256) in the hypo-endemic. The corresponding prevalences of nodules among the adult male subjects were 77.7% (171/220) and 2.3% (2/86). The most common onchocercal skin lesion in the hyper-endemic community was chronic papular onchodermatitis (CPOD) manifested by itching, which was often very severe. There was a strong association between skin itching and endemicity (r = 0.75; P < 0.001). The prevalence of CPOD in the hyper-endemic community was significantly higher in males than females (P< 0.001). CPOD was only observed in subjects aged > or = 7 years. Many of the subjects were checked for microfilaridermia, by skin-snipping. The prevalence of microfilaridermia [58.2% (393/675) v. 6.2% (3/48)] and its geometric mean intensity (8.9 v. 1.0 microfilariae/mg skin snip) were both higher in the hyper-endemic community than the hypo-endemic. Itching appears to be related to reactive onchodermatitis.

An investigation of human infection with Onchocerca volvulus and the resulting clinical disease was carried out for the Nigerian National Onchocerciasis Control Programme between July and August 1989 [corrected]. The survey covered 10.6% of the rural population in 41 savanna villages of central Nigeria. Of the 8451 self-selected individuals examined, 900 (10.6%) had skin microfilariae (Mf). There were differences between villages in both endemicity and intensity of infection, but in general the number of both Mf carriers and cases of clinical onchocerciasis increased with age. The disease in the Mf carriers showed as blindness (0.8%), onchocercal nodules (0.6%), leopard skin (1.6%) and pruritus (2.8%). Of 35 persons with lymphatic complications, 19 had hanging groin, 10 had elephantiasis and six had hydrocoele. Onchocerciasis was mesoendemic in the rocky northern escarpments, and became hypoendemic and sporadic in the southern uplands of sedimentary geological origin.