Wildlife surveys detect Trypanosoma brucei gambiense in duikers and mangabeys in Gabonese historical and active foci of human African trypanosomiasis.

Human African trypanosomiasis (HAT) continues to represent a public health concern in Central Africa, particularly in Gabon, where sporadic cases persist in historical foci despite ongoing elimination efforts. The existence of an autonomous sylvatic cycle involving non-human animal reservoirs has been hypothesized but remains insufficiently documented. The objective of this study was to characterise the diversity of trypanosomes present in wild animals from a number of historically and currently endemic provinces of Gabon. Between 2019 and 2022, a total of 240 blood samples were collected from wild non-human primates (n = 172) and ungulates (n = 68). The molecular identification of trypanosomes was performed using nested PCR targeting the 18S rRNA gene, followed by sequencing and phylogenetic analysis. The overall infection rate was 12.1%. A higher prevalence was observed in great apes (gorillas: 36.4%) than in ungulates. Six trypanosome species and subspecies were identified, belonging to different subgenera: T. brucei gambiense and T. brucei brucei; T. congolense; T. vivax; as well as T. simiae (subgenus Nannomonas) and T. theileri (subgenus Megatrypanum). The most prevalent species detected were T. brucei brucei and T. congolense. Trypanosoma brucei gambiense was identified in mangabeys and duikers from the Ogooué-Maritime and Haut-Ogooué provinces. Although no statistically significant associations were found between infection status and factors such as sex, age, or season, ecological and spatial trends were observed. The analysis of host-parasite interactions demonstrated that hosts, including duikers and monkeys, can harbor multiple Trypanosoma species, indicating their role as reservoirs for diverse parasites. These findings provide further evidence supporting the hypothesis of the circulation of T. brucei gambiense in Gabonese wildlife, and underscore the potential for wild animals to serve as cryptic reservoirs. Integration of eco-epidemiological surveillance within a One Health framework is imperative for strengthening elimination strategies and reducing the risk of HAT resurgence or zoonotic emergence.