Molecular Epidemiology and Genetic Diversity of Trypanosoma brucei gambiense in Human and Animal Reservoirs in the Benue Valley, North Central Nigeria

This dissertation provides the first molecular epidemiological and genetic diversity analysis of Trypanosoma brucei gambiense in human sleeping sickness foci and animal reservoir hosts in the Benue Valley, Benue and Kogi States, North Central Nigeria. Human African trypanosomiasis (HAT) caused by T. b. gambiense persists in historical foci along the Benue River, yet the genetic relationships between human and animal parasite populations, the role of domestic animals as maintenance hosts, and the molecular epidemiology of transmission in this focus remain uncharacterised. The dissertation employs a systematic sampling design across 18 communities in the historical HAT belt. Trypanosomes were detected in humans by CATT and lymph node aspirates, in domestic animals by buffy coat technique and PCR, and in Glossina by dissection and PCR. Molecular genotyping using seven microsatellite loci on 125 characterised T. b. gambiense isolates from humans, cattle, and pigs was conducted. Population structure and gene flow were analysed using STRUCTURE, AMOVA, and isolation-by-distance models. All human isolates belonged to Group 1 T. b. gambiense. Significant genetic structuring between villages (FST = 0.18) demonstrated limited long-range dispersal. Pig-derived isolates showed the highest genetic similarity to sympatric human isolates, supporting pigs as the primary domestic animal reservoir in this focus. The dissertation delivers an original genetic map of T. b. gambiense transmission dynamics for the Benue Valley and proposes pig-targeted trypanocide treatment as a priority intervention for HAT elimination. Keywords: Trypanosoma brucei gambiense, molecular epidemiology, sleeping sickness, Benue Valley, animal reservoir.