Molecular Detection and Phylogenetic Analysis of Trypanosoma brucei gambiense in Glossina Populations in Cross River State

Surveillance of Trypanosoma brucei gambiense in tsetse fly populations is a critical component of human African trypanosomiasis elimination monitoring, given the risk of cryptic transmission in forested regions of South South Nigeria. This study applied molecular detection and phylogenetic analysis to investigate T. b. gambiense presence in Glossina populations in Cross River State, South South Nigeria. A total of 420 Glossina palpalis flies were collected using biconical and Epsilon traps deployed over four months in three forest game reserves. DNA was extracted from thoraces and screened by nested PCR targeting the T. b. gambiense TgsGP gene. Positive samples were sequenced, and phylogenetic analysis was performed using maximum likelihood methods. T. b. gambiense DNA was detected in 2.6 percent of sampled flies, all from the deep forest zone of Oban Hills. Phylogenetic analysis clustered Nigerian isolates within West African Group 1 T. b. gambiense clade, consistent with historical isolate data. No clinical cases had been detected in adjacent human communities in the preceding five years, but serosurveillance gap was noted. The findings demonstrate cryptic maintenance of transmission potential in Cross River State and argue for inclusion of molecular vector surveillance in Nigeria's post-elimination validation programme. Keywords: Trypanosoma brucei gambiense, tsetse fly, molecular detection, Cross River State, sleeping sickness surveillance.