Onchocerciasis in the upper Imo river basin, Nigeria: prevalence and comparative study of waist and shoulder snips from mesoendemic communities

Onchocerciasis is endemic in the Imo River Basin, Nigeria. This study was aimed at assessing the prevalence and intensity of microfilaria of Onchocerca volvulus in the area. A cross-sectional study was carried out in the Okigwe Local Government Area, Imo State, Nigeria. Two skin snips [one from the waist and another from the shoulder] were taken from 1024 individuals examined. The survey coverage was high [91.8% of the study population]. An individual was considered mf positive if either of the waist or shoulder snips or both were mf positive. The SPSS for Windows package was used for entering and analysis of data. Thirty-seven percentage of those examined was positive for Onchocerca volvulus microfilariae [39.2% of males and 34.9% of females]. The mf prevalence increased steadily with increasing age to reach 70.4% in the oldest age group. The overall mf Geometric Mean Intensity among mf positive individuals was 16 mf/skin snip and was significantly higher among males [18 mf/skin snip] than females [14 mf/skin snip] [p<0.01]. A scatter plot of microfilariae numbers in snips from the waist against numbers in snips from the shoulder of the same individuals, showed close correlation [Pearson's correlation coefficient=+0.90; p<0.01], and those with mf intensities below 10 mf/snip had a more scattering tendency away from the regression line than those with higher mf intensities. Onchocerciasis is a public health concern in the area. Perhaps, 10 mf/snip is critical intensity threshold for reliable sampling using corneo-scleral punch

Clinical manifestations of mesoendemic onchocerciasis in an area with multiple filarial species

The Imo River Basin, Nigeria is endemic for onchocerciasis, bancroftian filariasis, loaiasis and mansonellosis. This study was aimed at determining the clinical manifestations of onchocerciasis in the region. A cross- sectional study was carried out in 2006 in Umuowaibu I and Ndiorji communities in Okigwe Local Government Area of Imo State, Nigeria. Consenting individuals were examined for various gradations of skin manifestations, subcutaneous nodules, and visual impairments by qualified medical doctors. Five categories of skin manifestations were observed, namely permanent itching, onchodermatitis, atrophy of ski, leopard skin, and sowda. A total of 1024 individuals were examined. The prevalence of the skin manifestations were permanent itching [2.5%], onchodermatitis [3.9%], atrophy of the skin [5.8%], leopard skin [22.1%], and sowda [0.1%]. The prevalence of subcutaneous nodules was 25.3%, but 88.9% among the oldest age group, and mostly found in lower half of body. The majority of cases of visual acuity problems [6.8% overall prevalence] were in the oldest age groups. Among those who were >/= 20 years old, the prevalence of visual acuity problems was significantly higher in females than in males [chi[2] -test; P<0.05]. Only two of the examined persons were observed to be blind. Clinical manifestations of onchocerciasis are perhaps more intense in the area probably because of presence of endemic infections of other filarial species