Browsing Trypanosomiasis/Sleeping Sickness by Subjects
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Card Agglutination Test for Trypanosomiasis (CATT) End-Dilution Titer and Cerebrospinal Fluid Cell Count as Predictors of Human African Trypanosomiasis (Trypanosoma brucei gambiense) Among Serologically Suspected Individuals in Southern Sudan.The diagnosis of human African trypanosomiasis (HAT) due to Trypanosoma brucei gambiense relies on an initial serologic screening with the card agglutination test for trypanosomiasis (CATT) for T. b. gambiense, followed by parasitologic confirmation in most endemic areas. Unfortunately, field parasitologic methods lack sensitivity and the management of serologically suspected individuals (i.e., individuals with a positive CATT result but negative parasitology) remains controversial. In Kajo-Keji County in southern Sudan, we prospectively collected sociodemographic and laboratory data of a cohort of 2,274 serologically suspected individuals. Thirty-three percent (n = 749) attended at least one follow-up visit and HAT was confirmed in 64 (9%) cases. Individuals with lower initial CATT-plasma (CATT-P) end-dilution titers had lowest risks (10.4 and 13.8/100 person-years for 1:4 and 1:8 titers, respectively) that significantly increased for higher dilutions: relative risks = 5.1 (95% confidence interval [CI] = 2.6-9.5) and 4.6 (95% CI = 2.8-9.8) for 1:16 and 1:32 titers, respectively. The cumulative yearly risk was also high (76%) in individuals found with 11-20 cells in the cerebrospinal fluid, but this involved only eight patients. Adjustment for potential confounders did not affect the results. In conclusion, treatment with pentamidine should be considered for all serologically suspected individuals with a CATT-P end-dilution titer >/= 1:16 in areas of a moderate to high prevalence of HAT.
Field evaluation of the CATT/Trypanosoma brucei gambiense on blood-impregnated filter papers for diagnosis of human African trypanosomiasis in southern Sudan.Most Human African Trypanosomiasis (HAT) control programmes in areas endemic for Trypanosoma brucei gambiense rely on a strategy of active mass screening with the Card Agglutination Test for Trypanosomiasis (CATT)/T. b. gambiense. We evaluated the performance, stability and reproducibility of the CATT/T. b. gambiense on blood-impregnated filter papers (CATT-FP) in Kajo-Keji County, South-Sudan, where some areas are inaccessible to mobile teams. The CATT-FP was performed with a group of 100 people with a positive CATT on whole blood including 17 confirmed HAT patients and the results were compared with the CATT on plasma (CATT-P). The CATT-FP was repeated on impregnated filter papers stored at ambient and refrigerated temperature for 1, 3, 7 and 14 days. Another 82 patients with HAT, including 78 with a positive parasitology, were tested with the CATT-FP and duplicate filter paper samples were sent to a reference laboratory to assess reproducibility. The CATT-FP was positive in 90 of 99 patients with HAT (sensitivity: 91%). It was less sensitive than the CATT-P (mean dilution difference: -2.5). There was no significant loss of sensitivity after storage for up to 14 days both at ambient and cool temperature. Reproducibility of the CATT-FP was found to be excellent (kappa: 0.84). The CATT-FP can therefore be recommended as a screening test for HAT in areas where the use of CATT-P is not possible. Further studies on larger population samples in different endemic foci are still needed before the CATT-FP can be recommended for universal use.
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.