Diversity of response to Trypanosoma brucei gambiense infections in the Forecariah mangrove focus (Guinea): perspectives for a better control of sleeping sickness

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.