Longitudinal study of onchocerciasis in Bebeka-Ethiopia

This paper describes the morbidity, intensity and prevalence of onchocerciasis in an endemic area of Ethiopia, using a cross-sectional study (n = 425) and a longitudinal cohort study (n = 98). During the study period (February-October 1987), the increase in intensity and in number of cases with dermal lesions was highly significant (p < 0.005) when compared with the increase in the microfilarial positivity rate (p < 0.1). Since the serial increase in dermatologic problems was not directly correlated with an increase in O. volvulus microfilarial prevalence or intensity, it is suggested that hyper-sensitivity responses to repeated Simulium bites might exacerbate onchocercal dermal lesions. The controversy concerning Simulium bites as a cause of lesions mimicking those due to O. volvulus parasites is discussed.