A cross-sectional survey of onchocerciasis in male fieldrnworkers was conducted in Teppi Coffee Plantation Project, BayarnFarm, in November-December 1991.rnThe objectives were to assess the magnitude of the problem, tornmeasure the sensitivity of various diagnostic procedures, to assessrnthe effect on onchocerciasis infection of various exposure factors,rnand to determine the effect of the disease on work productivity.rnA total of 196 study subjects participated in the study. Theyrnwere interviewed to assess their exposure status and complaints ofrnrheumatism. Physical examination was conducted and measurements onrnweight and height, and on visual acuity were taken. Parasitologicalrndiagnosis was based on skin biopsies from the calf, hip, andrnscapula bilaterally. Labor cards were reviewed over the previousrntwelve months to assess various indicators of work productivity. Arncase-control analysis was performed.rnIt was found that the prevalence rate of onchocerciasis wasrnvery high (82.8%), as compared to other studies conducted inrnEthiopia. This was ascribed to the selection of the studyrnpopulation, whose age, gender, and exposure status made it prone torncontract the disease. No study subject had any detectable visualrnimpairment and other chronic manifestations were few. This wasrnattributed partially to the "healthy worker effect".rnParasitological diagnosis detected 93.8% of the cases whilernclinical diagnosis only detected 35.8% of the cases.rnvrnIn this study it was not possible to establish the protectiverneffect of being always fully clothed at work and having less riverassociatedrnactivities. This was attributed to the cumulative effectrnof exposure to many different sources due to the long sojourn ofrnstudy subjects in endemic areas .rnWorkers with onchocerciasis were significantly more likely tornbe absent from work due to illness and other reasons, and earnedrnsignificantly less wages than workers without onchocerciasis, thusrndemonstrating that non-blinding onchocerciasis has a negativernimpact on work productivity