The effectiveness of active population screening and treatment for sleeping sickness control in the Democratic Republic of Congo

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Abstract
The human African trypanosomiasis (HAT) control programme of the Democratic Republic of Congo (DRC) uses mass screening with the card agglutination test for trypanosomes (CATT). We looked at the contribution of CATT and improved parasitological confirmation to the effectiveness of screening and treatment. The effectiveness of the screening and treatment process is measured by the percentage of HAT cases that is effectively cured after a single round of screening. The process is analysed in five steps: (i) the attendance at the screening, (ii) the sensitivity of the screening procedure, (iii) the sensitivity of the parasitological confirmation, (iv) the proportion of the confirmed cases that effectively receive treatment and (v) the cure rate of the treatment. We used a simplified model that multiplies proportions of infected persons that go through each step. We estimated these parameters using a combination of routine data collected by the national control programme over the period January 1997 to December 1998 and published data. For varying attendance rates we compared the effectiveness of screening strategies based on CATT or on CATT combined with improved parasitological confirmation by mini anion exchange column technique (mAECT) with the previously used strategy based on palpation of neck glands and microscopy alone. The model shows that overall effectiveness of the active case detection and treatment strategy is <50% under most scenarios. Attendance rates averaged 74% but showed considerable regional variability and are a major problem in some areas of DRC. The CATT and replacing traditional parasitology by mAECT increases the sensitivity of the screening but a substantial part of the gains are lost at other stages of the screening process. Improvements of the HAT screening process such as introduction of CATT or mAECT only make sense if other parameters and attendance rate in particular are optimized at the same time.