Determinants of onchocerciasis infection and its impact on health and productivity in Teppi Coffee Plantation field workers

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Addis Ababa University


A cross- sectional survey of onchocerciasis in male field workers was conducte~ in Teppi Coffee Plantation Project, Baya Farm, in November-December 1991. The objectives were to assess the magnitude of the problem, to measure the sensitivity of various diagnostic procedures, to assess the effect on onchocerciasis infection of various exposure factors, and to determine the effect of the disease on work productivity. A total of 196 study subjects participated in the study. They were interviewed to assess their exposure status and complaints of rheumatism. Physical examination was conducted and measurements on weight and height, and on visual acuity were taken. Parasitological diagnosis was based on - skin biopsies from the calf, hip, and scapula bilaterally. Labor cards were reviewed over the previous twelve months to assess various indicators of work productivity. A case-control analysis was performed. It was found that the prevalence rate of onchocerciasis was very high (82.8%), as compared to other studies conducted in Ethiopia. This was ascribed to the selection of the study population, whose age, gender, and exposure status made it prone to contract the disease. No study subject had any detectable visual impairment and other chronic manifestations were few. This was attributed partially to the "healthy worker effect". Parasitological diagnosis detected 93.8% of the cases while clinical diagnosis only detected 35 . 8% of the cases.In this study it was not possible to establish the protective effect of being always fully clothed at work and having less riverassociated activities. This was attributed to the cumulative effect of exposure to many different sources due to the long sojourn of study subjects in endemic areas. Workers with onchocerciasis were significantly more likely to be absent from work due to illness and other reasons, and earned significantly less wages than workers without onchocerciasis, thus demonstrating that non-blinding onchocerciasis has a negative impact on work productivity.



Determinants of onchocerciasis infection