Epizootiology and mitochondrial genetic diversity of Taenia hydatigena in Nigerian small ruminants: Implications for one health control.

Taenia hydatigena is a globally distributed cestode of veterinary importance that infects canids (definitive hosts) and ungulate livestock (intermediate hosts). Although non-zoonotic, its transmission ecology overlaps with zoonotic taeniids, making surveillance relevant within a One Health framework. Its epidemiology and genetic diversity remain poorly understood in West Africa. Nigeria, with its large and mobile livestock populations, provides a critical setting for investigating parasite transmission and phylogeographic dynamics. We conducted a large-scale abattoir survey of small ruminants (goats and sheep) across four major Nigerian states to assess infection prevalence, organ tropism, and demographic correlates. T. hydatigena cysticerci were characterized using full-length mitochondrial nad1 and nad4 genes, as well as concatenated nad1-nad4 datasets. Sequence diversity, haplotype structure, and phylogenetic relationships were analyzed in comparison with global T. hydatigena isolates. Among 1726 small ruminants examined, 8.9% (153/1726) were infected, with infection biased toward adult animals and cysts predominantly localized in mesenteric and omental tissues. Mitochondrial analyses revealed high haplotype richness, with nad4 showing greater variability than nad1, and concatenated sequences providing superior phylogenetic resolution. Nigerian isolates clustered both locally and globally, indicating long-standing endemicity reinforced by porous livestock trade networks. Unique regional haplotypes highlighted West Africa's contribution to global T. hydatigena diversity. This study provides the most comprehensive molecular epidemiological assessment of T. hydatigena in Nigeria to date, underscoring an endemic, economically important burden and the need for integrated One Health interventions targeting the dog-livestock transmission cycle.