A modelling assessment of short- and medium-term risks of programme interruptions for gambiense human African trypanosomiasis in the DRC

Abstract

Gambiense human African trypanosomiasis (gHAT) is a deadly vector-borne, neglected tropical disease found in West and Central Africa targeted for elimination of transmission (EoT) by 2030. The recent pandemic has illustrated how it can be important to quantify the impact that unplanned disruption to programme activities may have in achieving elimination of transmission. We used a previously developed model of gHAT fitted to data from the Democratic Republic of Congo, a country with the highest global case burden, to explore how interruptions to intervention activities, due to e.g. COVID-19, Ebola or political instability, could impact progress towards EoT and gHAT burden. We simulated transmission and reporting dynamics in 38 health zones under six interruption scenarios lasting for nine or twenty-one months. Included in the interruption scenarios are the cessation of active screening in all scenarios and a reduction in passive detection rates and a delay or suspension of vector control deployments in some scenarios. Our results indicate that, even under the most extreme 21-month interruption scenario, EoT is not predicted to be delayed by more than one additional year compared to the length of the interruption. If existing vector control deployments continue, we predict no delay in achieving EoT even when both active and passive screening activities are interrupted. If passive screening remains fully functional, we expect a marginal negative impact on transmission, however this depends on the strength of passive screening in each health zone. We predict a pronounced increase in additional gHAT disease burden (morbidity and mortality) in many health zones if both active and passive screening were interrupted compared to the interruption of active screening alone. The ability to continue existing vector control during medical activity interruption is also predicted to avert a moderate proportion of disease burden.Author SummaryWhilst the COVID-19 pandemic has produced wide-spread disruption for many disease programmes there are also a range of other factors that continue to risk programme interruptions including other disease outbreaks (e.g. Ebola, cholera, yellow fever, and measles) and the potential for political instability. In this study we examine the impact of interruptions by external factors to the gambiense human African trypanosomiasis (gHAT, sleeping sickness) elimination programme of the Democratic Republic of the Congo, a country which has the highest global case burden. We use our previously fitted gHAT model to simulate how transmission dynamics might be impacted by disruption to medical interventions and (where relevant) vector control activities in 38 health zones of the former Bandundu province. For each of the six interruption scenarios we use the model to forecast case numbers and disease burden as well as estimating the expected years and probabilities of elimination of transmission. This analysis provides invaluable insight into the impact that interruptions of any persuasion could have on burden, case reporting and time to achieve elimination of transmission of gHAT in the Democratic Republic of the Congo.