Molecular characterization and phylogenetic analysis of Fasciola gigantica from Nigeria.

Fasciola gigantica is considered the major pathogen causing fasciolosis in Africa; however, molecular characterization of this fluke has not been adequately elucidated. It is important to scientifically elucidate the dispersal history of F. gigantica by analyzing its genetic diversity. Fasciola flukes from Nigeria were analyzed using nuclear and mitochondrial DNA markers. A total of 172 Fasciola flukes collected from cattle were identified as F. gigantica because they displayed the F. gigantica fragment pattern in multiplex PCR for the nuclear marker, phosphoenolpyruvate carboxykinase (pepck). In total, 70 haplotypes were detected from Nigerian F. gigantica on the basis of the concatenated sequence of mitochondrial NADH dehydrogenase subunit 1 (nad1) and cytochrome c oxidase 1 (cox1). The index of neutrality (Fu's Fs) suggests rapid expansion of the Nigerian F. gigantica population. Although four haplogroups, Nigeria 1A, 1B, 2A, and 2B, were detected from Nigerian F. gigantica, a climate-specific genetic structure was not observed among F. gigantica populations from three agro-climatic regions (Sahel, Savannah, and Forest). This is probably because of the frequent transportation of livestock from one part of the country to the other. Nigeria 1A and 1B had close relationships with the Egyptian population of F. gigantica, whereas Nigeria 2A and 2B were comparatively related to the Zambian population. No haplotype was shared among the three countries, and it therefore is difficult to estimate the dispersal route of F. gigantica within the African continent.