Investigation of an epidemic of seasonal ataxia in Ikare, western Nigeria

Abstract

Seasonal outbreaks of an acute ataxic syndrome occur annually in parts of South-Western Nigeria, characterized by cerebellar ataxia, nystagmus and varying levels of impaired consciousness following consumption of the roasted larvae of Anaphe venata Butler (Lepidoptera, Notodontidae). An investigation of an epidemic in Ikare, headquarters of the Akoko north-east local Government in Western Nigeria (pop. 60,000) in the 1993 disease season is reported. The diagnosis of seasonal ataxia was verified in 34 consecutive new admissions (M:F 1:3.25, median age 29 years, range 2-70 years). All were of low socio-economic status, and had consumed the larvae of Anaphe venata prior to the onset of disease. There were 1,126 admissions for the seasonal ataxic syndrome in Ikare in the 1993 season, with an estimated attack rate of 1.87%. The peak incidence was in August, when patients with the syndrome accounted for 71% of all hospital admissions. There was no mortality. Control measures included therapy with high-potency multivitamins and health education.