A NEW FOCUS OF ONCHOCERCIASIS IN MWANZA DISTRICT, MALAWI

Anecdotal information suggested that a new focus of onchocerciasis had recently developed in Mwanza in Malawi, a district not contiguous wit h Thyolo, the only district in Malawi with recognized autochthonous tr ansmission. We carried out a survey of the northern half of Mwanza dis trict, randomly selecting 62 villages for assessment. Two iliac crest skin snips were taken from 2215 residents over the age of 15 years; on e-quarter had Onchocerca volvulus microfilariae. Prevalence increased with age and was higher overall among men than women. The age-adjusted prevalence among migrants from Thyolo was 31%. Among residents who ha d never been outside Mwanza, the gender-specific prevalences and micro filarial loads were similar. The intensity of infection was low. Autoc hthonous transmission of O. volvulus has thus been demonstrated in Mwa nza and illustrates the possibility of the spread of the disease to ne w foci in Malawi and the surrounding countries, due to significant pop ulation shifts.