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Update of transmission modelling and projections of gambiense human African trypanosomiasis in the Mandoul focus, Chad
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Rock, Kat S., Huang, Ching-I, Crump, Ronald E., Bessell, Paul R., Brown, Paul E., Tirados, Inaki, Solano, Philippe, Antillon, Marina, Picado, Albert, Mbainda, Severin, Darnas, Justin, Crowley, Emily, Torr, Steve J. and Peka, Mallaye (2022) Update of transmission modelling and projections of gambiense human African trypanosomiasis in the Mandoul focus, Chad. Infectious Diseases of Poverty, 11 (1). 11. doi:10.1186/s40249-022-00934-8 ISSN 2049-9957.
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Official URL: https://doi.org/10.1186/s40249-022-00934-8
Abstract
Background: In recent years, a programme of vector control, screening and treatment of gambiense human African trypanosomiasis (gHAT) infections led to a rapid decline in cases in the Mandoul focus of Chad. To represent the biology of transmission between humans and tsetse, we previously developed a mechanistic transmission model, fitted to data between 2000 and 2013 which suggested that transmission was interrupted by 2015. The present study outlines refinements to the model to: (1) Assess whether elimination of transmission has already been achieved despite low-level case reporting; (2) quantify the role of intensified interventions in transmission reduction; and (3) predict the trajectory of gHAT in Mandoul for the next decade under different strategies. Method: Our previous gHAT transmission model for Mandoul was updated using human case data (2000–2019) and a series of model refinements. These include how diagnostic specificity is incorporated into the model and improvements to the fitting method (increased variance in observed case reporting and how underreporting and improvements to passive screening are captured). A side-by-side comparison of fitting to case data was performed between the models. Results: We estimated 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 1.5-fold for stage 2. We find that whilst the diagnostic algorithm for active screening is estimated to be highly specific (95% credible interval (CI) 99.9–100%, Specificity = 99.9%), the high screening and low infection levels mean that some recently reported cases with no parasitological confirmation might be false positives. We also find that the focus-wide tsetse reduction estimated through model fitting (95% CI 96.1–99.6%, Reduction = 99.1%) is comparable to the reduction previously measured by the decline in tsetse catches from monitoring traps. In line with previous results, the model suggests that transmission was interrupted in 2015 due to intensified interventions. Conclusions: We recommend that additional confirmatory testing is performed in Mandoul to ensure the endgame can be carefully monitored. More specific measurement of cases, would better inform when it is safe to stop active screening and vector control, provided there is a strong passive surveillance system in place. Graphical Abstract:
| Item Type: | Journal Article | ||||||||||||||||||||||||
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| Subjects: | Q Science > QL Zoology R Medicine > RA Public aspects of medicine R Medicine > RC Internal medicine |
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| Divisions: | Faculty of Science, Engineering and Medicine > Science > Mathematics | ||||||||||||||||||||||||
| SWORD Depositor: | Library Publications Router | ||||||||||||||||||||||||
| Library of Congress Subject Headings (LCSH): | African trypanosomiasis -- Chad, African trypanosomiasis -- Transmission -- Mathematical models -- Chad, Tsetse-flies -- Control, Vector control | ||||||||||||||||||||||||
| Journal or Publication Title: | Infectious Diseases of Poverty | ||||||||||||||||||||||||
| Publisher: | BioMed Central | ||||||||||||||||||||||||
| ISSN: | 2049-9957 | ||||||||||||||||||||||||
| Official Date: | 2022 | ||||||||||||||||||||||||
| Dates: |
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| Volume: | 11 | ||||||||||||||||||||||||
| Number: | 1 | ||||||||||||||||||||||||
| Article Number: | 11 | ||||||||||||||||||||||||
| DOI: | 10.1186/s40249-022-00934-8 | ||||||||||||||||||||||||
| Status: | Peer Reviewed | ||||||||||||||||||||||||
| Publication Status: | Published | ||||||||||||||||||||||||
| Reuse Statement (publisher, data, author rights): | ** From Springer Nature via Jisc Publications Router ** History: received 14-10-2021; accepted 03-01-2022; registration 04-01-2022; pub-electronic 24-01-2022; online 24-01-2022; collection 12-2022. ** Licence for this article: http://creativecommons.org/licenses/by/4.0/ | ||||||||||||||||||||||||
| Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||||||||||||||
| Date of first compliant deposit: | 1 February 2022 | ||||||||||||||||||||||||
| Date of first compliant Open Access: | 1 February 2022 | ||||||||||||||||||||||||
| RIOXX Funder/Project Grant: |
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