onchocerciasis in the upper imo river basin, nigeria: prevalence and comparative study of waist and shoulder snips from mesoen¬demic communities

background: 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. methods: 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. results: 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. conclusion: onchocerciasis is a public health concern in the area. perhaps, 10 mf/snip is critical intensity threshold for reliable sampling using corneo-scleral punch.