Relationships between Onchocerca volvulus microfilaraemia and the clinical manifestations of meso-endemic onchocerciasis in the Umuowaibu and Ndiorji communities in southeastern Nigeria

Abstract

The study was aimed at determining the relationship between Onchocerca volvulus microfilaraemia and the clinical manifestations of onchocerciasis in the endemic Umuowaibu and Ndiorji communities in southeastern Nigeria. Two skin snips (each from the shoulder and the waist) were taken for parasitological examination from each individual during daytime using a Walser corneoscleral punch. These individuals were also examined for gradations of skin manifestations and visual impairments using standard criteria. In all, 62 (49.6%) of those with chronic skin damage were positive for O. volvulus microfilaraemia, whereas 317 (35.3%) of those without chronic skin damage were positive for O. volvulus microfilaraemia. This difference was significant (?2-test; p < 0.001). The mf GMI of those with chronic skin damage (13 mf/snip) was significantly lower than the mf GMI of those without chronic skin damage (16 mf/snip) (t-test; p < 0.001). The mf prevalence of those with leopard skin (67.7%) was significantly higher than that in those without leopard skin (28.3%) (?2-test; p < 0.001). The mf GMI of those with leopard skin was significantly higher than that of those without leopard skin (t-test; p < 0.001). Most cases of leopard skin were seen in those aged 20 years and above. Of those with subcutaneous nodules, 63.7% were O. volvulus mf positive, with an overall mf GMI of 19 mf skin snip. Among those without subcutaneous nodules, 28.0% were O. volvulus mf positive with an mf GMI of 14 mf/skin snip. These differences were statistically significant (?2-test; p < 0.001; and t-test; p < 0.001). The prevalence of O. volvulus microfilaraemia was high among those who presented visual acuity problems with mf prevalence of 57.1% and mf GMI of 20 mf/skin snip. For those who did not present visual acuity problems, 35.5% were positive for O. volvulus microfilaraemia with mf GMI of 15 mf/skin snip. The difference in mf GMI was also statistically significant (t-test; p < 0.001). The difference in mf GMI was also statistically significant (t-test; p < 0.001). In conclusion, the O volvulus microfilaraemia was closely associated with most clinical manifestations especially among older age groups in the meso-endemic area.

Keywords: Onchocerciasis, chronic inflammatory skin damage, leopard skin, subcutaneous nodules, visual acuity, Onchocerca volvulus, Nigeria