Ebola outbreak brings to light an unforeseen impact of tsetse control on sleeping sickness transmission in Guinea

Abstract

In addition to the thousands of deaths due the unprecedented ebola outbreak that stroke West Africa (2014-2016), national health systems in affected countries were deeply challenged impacting a number of diseases control programs. Here we describe the case of Human African Trypanosomiasis (HAT), a deadly neglected tropical disease due to a trypanosome transmitted by tsetse flies for which no vaccine nor chemoprophylaxis exists. Data are presented for the disease focus of Boffa in Guinea where a pilot elimination project combining medical screening and vector control was launched in 2012. During ebola, HAT active screening activities were postponed and passive surveillance also was progressively impaired. However, tsetse control using small insecticide impregnated targets could be maintained. The over two years disruption of screening activities led to a dramatic increase of HAT prevalence, from 0.7% in 2013 (21/2885) to 2% (69/3448) in 2016, reaching epidemic levels (>5%) in some villages. In deep contrast, control levels reached in 2013 (0.1%; 7/6564) were maintained in areas covered with impregnated targets as no cases were found in 2016 (0/799). In Boffa, ebola has thus incidentally provided a unique framework to assess the impact of current HAT control strategies. A first lesson is that the “screen and treat” strategy is fragile as rapid bursts of the disease may occur in case of disruption. A second lesson is that vector control reducing human-tsetse contacts, even implemented alone, is effective in providing a good level of protection against infection. This advocates for a greater attention being paid to the combination of tsetse control together with medical activities in aiming to reach the HAT elimination objective in Africa.

Quantifying epidemiological drivers of gambiense human African Trypanosomiasis across the Democratic Republic of Congo

“…This would be very pronounced if the model is subsequently used to make projections of future vector control impact. We are reassured by various other recent studies that our tsetse-transmission assumption is valid as (i) the host-vector gHAT model predictions for regions with vector control appear to match the case reductions well [7] and (ii) the natural experiment which occurred in Guinea during the 2014-15 West African Ebola outbreak found that even following interruption of medical screening activities, regions that had vector control remaining in situ had much lower case burden following resumption of screening than those without [41,42].…”

Predicting the impact of COVID-19 interruptions on transmission of gambiense human African trypanosomiasis in two health zones of the Democratic Republic of Congo

“…In the Ebola outbreak of 2014–2015, the interruption to active screening and passive surveillance is thought to have caused an increase in transmission in the affected areas, except in places where small insecticide impregnated targets could be maintained, indicating tsetse control is likely protective during medical interruptions if it remains in situ. 7 , 25 …”

Demonstrating the sustainability of capacity strengthening amidst COVID-19

“…In the Ebola outbreak, GHAT medical activities had to be suspended but tiny target deployment continued and was shown to have a significant impact on disease incidence. 8 The example from Guinea highlights the importance of continuing vector control during crises when medical surveys must be put on hold. As a result of our capacity strengthening work, vector control has been maintained during the COVID-19 pandemic, as recommended by the WHO, 3 providing vital protection to local communities.…”