Learning from local knowledge to improve disease surveillance: perceptions of the guinea worm illness experience.

Surveillance is an essential tool in any campaign to eradicate disease; guinea worm (dracunculiasis), which is targeted for eradication before the year 2000, is no exception. One criterion of an eradicable disease is that it be easy to recognize as the program advances. Few experts doubt that the experience of a meter-long subcutaneous worm protruding through a painful ulcer can be missed or confused with another disease, thus ensuring that guinea worm meets this criterion. Field experiences of anthropologists and health educators have shown that one should never assume that community perceptions of illness experience coincide fully with medical case definitions of disease. This paper describes efforts to learn how the Yoruba people of southwestern Nigeria perceive sobia, the local name for guinea worm. Qualitative methods including informal interview, village discussion and participant observation were used to discern a pattern of illness presentation and progression. Interestingly, local perceptions were found to include a variety of illness manifestations beyond the common clinical case definition of an emergent worm, thus creating the potential for a high level of false positive reports. Local knowledge was then used to design a pilot project that trained volunteers to become part of the surveillance network for the national eradication program. The volunteers, who were largely illiterate, were able to distinguish between cultural and clinical definitions, and submit quite accurate reports on the guinea worm status of their villages. Among the 164 volunteers, only two submitted false reports due to incorrect disease definition. In contrast local government health workers who were conducting village searches during the same period were significantly more likely to register false positive reports. The culturally sensitive training based on local knowledge received by the village volunteers is thought to have contributed to their superior performance.