Trypanosome circulation in hematophagous flies in livestock-rearing areas of southern Benin: prevalence, species diversity, and associations with vertebrate hosts

BACKGROUND: African animal trypanosomosis (AAT) remains a major obstacle to livestock productivity in sub-Saharan Africa, particularly in West Africa. In Benin, the epidemiological role of hematophagous flies in trypanosome circulation remains insufficiently documented. This study aimed to estimate the prevalence of Trypanosoma infections in these potential vectors and to characterize their blood meal sources in livestock interface zones of southern Benin. METHODS: Hematophagous flies were trapped using Vavoua, biconical and Nzi traps in 6 communes during dry and rainy seasons. The sample size for molecular analyses was determined using Cochran's formula, resulting in the selection of 384 individuals. These were analyzed by species-specific PCR targeting T. vivax, T. congolense (savannah and forest types) and T. brucei s.l. Blood meal identification was performed on engorged flies using multiplex PCR targeting cattle, humans, pigs, dogs and sheep. RESULTS: A total of 6550 hematophagous flies were collected across the 6 communes. The overall prevalence of trypanosomes was 13.8% (53/384; 95% CI 10.7-17.6%). T. vivax (6.8%) and T. congolense savannah type (6.5%) were the predominant species, while T. brucei s.l. was detected in only one specimen (0.3%); T. congolense forest was absent. The highest prevalences were recorded in Allada and Djidja (20.3% each). Dry season prevalence (16.1%) exceeded rainy season prevalence (11.8%), without statistically significant difference (p = 0.238). Blood meal analysis showed a predominance of cattle (44.4%), followed by humans (20.4%) and mixed sources. No significant association was observed between blood meal origin and infection status. CONCLUSIONS: These results suggest that non-tsetse hematophagous flies may contribute to trypanosome circulation in livestock systems of southern Benin. Their inclusion in trypanosomosis surveillance and control programs is strongly recommended.