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.

Seasonal ataxia: a case report of a disappearing disease

“…This pattern has been attributed to low levels of serum albumin in individuals who eventually develop the disease after exposure to the aetiologic agent (9). The clinico-epidemiologic descriptors of the subject namely female gender, low socioeconomic status, occurrence in October (rainy season) and the sudden onset of transient cerebellar ataxia, are all consistent with previous documentation of the disease (2,11). The absence of other features of increased cholinergic activity such as excessive salivation, diarrheoa and urinary retention in this patient is not out of place as few patients in past series had these symptoms (2,3).…”

“…Epidemics have since occurred in several parts of western Nigeria as documented by other workers [1]. Osuntokun investigated 50 patients involved in the 1972 epidemic [2] and noted that symptoms commenced usually within three hours of the local staple meal of yam, with the earliest symptom being vomiting. In his report, the most frequent symptom found was a 'parkinsonian' tremor with coexisting cerebellar signs.…”

“…More recently it has been suggested that the cerebellar symptoms of seasonal ataxia may be mediated by increased GABAergic, opioid and cholinergic neurotransmission [9]. A sex predilection has been reported in the occurrence of seasonal ataxia, with a female to male ratio of 3.25:1 and all age groups are vulnerable (2). The disease typically runs a benign self-limited course (2,3.)…”

“…A sex predilection has been reported in the occurrence of seasonal ataxia, with a female to male ratio of 3.25:1 and all age groups are vulnerable (2). The disease typically runs a benign self-limited course (2,3.) The most common presenting symptoms in patients with this disorder are tremors,unsteadiness while walking or standing, vomiting and dizziness (2,3).…”

“…The disease typically runs a benign self-limited course (2,3.) The most common presenting symptoms in patients with this disorder are tremors,unsteadiness while walking or standing, vomiting and dizziness (2,3). Less frequent symptoms include confusion, palpitations, excessive salivation, diarrheoa and urinary retention.…”