RESUMEN
BACKGROUND: A 17 year old female patient who presented to a tertiary Hospital in Addis Ababa with bilateral painful leg swelling of two months and shortness of breath, associated with cough and haemoptysis of one week duration was reported to the Ministry of Health and the Addis Ababa Health Bureau. The condition was later detected in 18 individuals from 4 households indicating occurrence of an outbreak of unknown cause in Addis Ababa which lasted during May-July 2008. OBJECTIVE: An outbreak investigation was initiated to identify the cause and prevent further spread, morbidity and mortality. METHODS: Using semi-structured questionnaire, quantitative assessment involving individual cases and affected households was conducted to detect aetiology and risk factors. Unaffected households as well as unaffected members of affected households were also included for comparison purpose. Record review of patients visiting hospitals was also done. Data were collected through house to house visits, and using interview of cases admitted to hospital. Samples of cooking oil were collected for laboratory testing. Data analysis was done using SPSS. RESULTS: A total of 182 patients, 50 (27.5%) males and 132 (72.5%) females, were identified till the outbreak was controlled fully. Age varied from 6-90 years. Death was confirmed in 12 cases, 8 of whom were female. The majority of the patients came from the adjoining Lideta (39.0%) and Kolfe Keranyo (31.9%) subcities. History of illness ranged from less than a week to 12 weeks before presentation. Out of the 106 household members of the 24 affected households identified during the first phase of the investigation, 83 were affected. Most family members who infrequently take meals at home, and children aged 3 years and below were spared. The 21 visited affected households from Kolfe keranyo, Lideta and Bole subcities bought cooking oil produced by a firm in Lideta subcity and all had bought their last supplies in March and April 2008. Samples of cooking food oil taken from this firm and from the affected households were found to have alkaloids of Argemone Mexicana. The number of new cases dropped to zero within 6 weeks after the source was closed. CONCLUSION: The occurrence of bilateral leg swelling in more than one family member of affected households, that bought cooking oil from the same source, sparing the toddlers, and those who infrequently take meals at home, further strengthened by laboratory confirmation of presence of argemone alkaloids in the cooking oil samples taken from the affected households and the common sources led to the diagnosis of the outbreak to be epidemic dropsy.