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

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.