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After intensive control efforts, human African trypanosomiasis (HAT) was declared eliminated in Côte d'Ivoire as a public health problem in December 2020 and the current objective is to achieve the interruption of the transmission (zero cases). Reaching this objective could be hindered by the existence of an animal reservoir of Trypanosoma (T.) brucei (b.) gambiense. In the framework of a study led in 2013 to assess the role of domestic animals in the epidemiology of HAT in the two last active foci from Côte d'Ivoire (Bonon and Sinfra), plasmas were sampled from four species of domestic animals for parasitological (microscopic examination by the buffy coat technique (BCT)), serological (immune trypanolysis (TL)) and molecular (specific PCR: TBR for T. brucei s.l., TCF for T. congolense forest type, TVW for T. vivax and PCR for T. b. gambiense) testing. In order to improve the understanding of the involvement/role of these animals in the transmission of T. b. gambiense, we have quantified in this study the IgG response to whole saliva extracts of Glossina palpalis gambiensis in order to perform an association analysis between anti-saliva responses and the positivity of diagnostic tests. Cattle and pigs had significantly higher rates of anti-tsetse saliva responses compared to goats and sheep (p 0.01). In addition, the anti-tsetse saliva responses were strongly associated with the parasitology (BCT+), serology (TL+) and PCR (TBR+ and TCF+) results (p 0.001). These associations indicate a high level of contacts between the positive/infected animals and tsetse flies. Our findings suggest that protecting cattle and pigs against tsetse bites could have a significant impact in reducing transmission of both animal and human trypanosome species, and advocates for a "One health" approach to better control African trypanosomosis in Côte d'Ivoire.

International audience; Control of human African trypanosomiasis (HAT) is highly dependent on the ability to detect and treat infected individuals. However, a number of individuals exposed to Trypanosoma brucei gambiense are able to control infection to undetectable levels in blood. They are long-term potential reservoirs and thus a threat for control strategies. Cytokine responses in whole blood stimulation assays were quantified in individuals with contrasting HAT status. Trypanosome-induced IFN-gamma production was only observed in "trypanotolerant" subjects suspected of harboring latent infections. This result contributes new insights into the immune responses associated with infection control and opens novel diagnosis perspectives regarding HAT elimination.

At a time when human African trypanosomiasis (HAT) elimination again seems a reachable goal in many parts of sub-Saharan Africa, it is becoming increasingly important to characterise the factors involved in disease resurgence or maintenance to develop sustainable control strategies. In this study conducted in the Forecariah mangrove focus in Guinea, HAT patients and serological suspects (SERO) were identified through mass screening of the population with the Card Agglutination Test for Trypanosomiasis (CATT) and were followed up for up to 2 years. Analysis of the samples collected during the follow-up of HAT patients and SERO was performed with PCR (TBR1/TBR2) and the trypanolysis serological test (TL) in order to clarify the role played by these individuals in the epidemiology of HAT. PCR positivity was higher in TL + than in SERO TL − (50% vs. 18%, respectively). Whereas CATT plasma titres decreased both in treated HAT patients and SERO TL − , SERO TL + maintained high CATT titres. Four out of 17 SERO TL + developed HAT during the study. These results strongly suggest that SERO TL + individuals are asymptomatic carriers. In the context where disease prevalence is sufficiently low, treating SERO TL + individual may thus be of crucial importance in order to cut transmission.