Abstract
AbstractBackgroundIn recent years, an integrated programme of vector control, screening and treatment of gambiense human African trypanosomiasis (gHAT) infections has led to a rapid decline in cases in the Mandoul disease focus of Chad. In this study, we assess whether elimination of transmission has already been achieved in the region despite low-level case reporting, quantify the role of intensified interventions in transmission reduction, and predict the trajectory of gHAT in Mandoul for the next decade under a range of control scenarios.MethodWe utilise human case data (2000–2019) to update a previous model of transmission of gHAT in Mandoul. We also test the updated model, which now has refined assumptions on diagnostic specificity of the current algorithm and an improved fitting method, via a data censoring approach.ResultsWe conclude that passive detection rates have increased due to improvements in diagnostic availability in fixed health facilities since 2015, by 2.1-fold for stage 1 detection, and by 1.5-fold for stage 2. We find that whilst the diagnostic algorithm for active screening is estimated to be highly specific (99.93%, 95% CI: 99.91–99.95%), the high screening level and limited remaining infection means that some recently reported cases might be false positives, especially the ones that were not parasitologically confirmed. We also find that the focus-wide tsetse vector reduction estimated through model fitting (99.1%, 95% CI: 96.1–99.6%) is comparable to the very high reduction previously measured by the decline in catches of tsetse from monitoring traps. In line with previous results, the model suggests that transmission was likely interrupted in 2015 as a result of intensified interventions.ConclusionsWe recommend that additional confirmatory testing is performed in Mandoul in order that the endgame can be carefully monitored now that infection levels are so low. More specific measurement of cases would better inform when it is safe to stop active screening and vector control.
Publisher
Cold Spring Harbor Laboratory
Reference29 articles.
1. WHO: ENDING the NEGLECT to ATTAIN the SUSTAINABLE DEVELOPMENT GOALS A road map for neglected tropical diseases. WHO library, 1–55 (2020)
2. Monitoring the elimination of human African trypanosomiasis at continental and country level: Update to 2018;PLoS Neglected Tropical Diseases,2020
3. Human African trypanosomiasis: current status and eradication efforts;CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources,2020
4. WHO: Control and surveillance of human African trypanosomiasis. Technical Report 984 (November 2013)
5. Updated estimate of the duration of the meningo-encephalitic stage in gambiense human African trypanosomiasis;BMC Research Notes,2015