Visceral leishmaniasis in southern Sudan: status of healthy villagers in epidemic conditions.

A combination of interview, serology and skin testing was used to investigate the status of apparently healthy villagers during a visceral leishmaniasis epidemic in southern Sudan. The number of people who had died equalled the number who were alive at the time of the survey. The direct agglutination test (DAT) identified 10% of the people as being serologically positive. Most young children (36/39) and 34% (22/64) of adults had neither positive serology nor skin test. About 64% (42/66) of adults had positive skin tests. In two villages, 54% and 76% of those over four years of age showed evidence of having been infected. The mortality associated with infection was estimated as at least 69%; 25% of those infected appeared to have cured spontaneously. The outcome for the remaining 6% was still doubtful. Even in this devastating epidemic there is, therefore, evidence of a considerable amount of infection without severe disease. Serological tests, while useful clinically, are apparently not useful for detecting early cases. Combined skin testing and serology produces a comprehensive though partially hypothetical picture.