Trypanosoma brucei gambiense trypanosomiasis in Terego county, northern Uganda, 1996: a lot quality assurance sampling survey.

We estimated the pre-intervention prevalence of Trypanosoma brucei gambiense (Tbg) trypanosomiasis using the lot quality assurance sampling (LQAS) methods in 14 parishes of Terego County in northern Uganda. A total of 826 participants were included in the survey sample in 1996. The prevalence of laboratory confirmed Tbg trypanosomiasis adjusted for parish population sizes was 2.2% (95% confidence interval =1.1-3.2). This estimate was consistent with the 1.1% period prevalence calculated on the basis of cases identified through passive and active screening in 1996-1999. Ranking of parishes in four categories according to LQAS analysis of the 1996 survey predicted the prevalences observed during the first round of active screening in the population in 1997-1998 (P < 0.0001, by chi-square test). Overall prevalence and ranking of parishes obtained with LQAS were validated by the results of the population screening, suggesting that these survey methods may be useful in the pre-intervention phase of sleeping sickness control programs.