Prevalence and genetic diversity of Fasciola species in cattle slaughtered around lake Albert, Kyoga and Victoria basins in Uganda

Abstract

Fascioliasis is caused by Fasciola species, with the intermediate host being freshwater and the definitive host being livestock and humans. We conducted a cross-sectional study to determine the prevalence and genetic diversity of Fasciola species in cattle slaughtered along Lake Albert, Kyoga, and Victoria basins in Uganda. Fecal samples and adult flukes were collected from cattle slaughtered. Mini flotac technique and microscopy was done to detect Fasciola eggs. Morphological identification of the flukes was done, and later DNA was extracted. Furthermore, PCR was performed by amplifying DNA polymerase delta (pold) and Phosphoenolpyruvate carboxykinase (pepck) genes for species identification. Additionally, Cytochrome C Oxidase 1 (cox 1), and NADH dehydrogenase subunit 1 (nad 1) genes were amplified for genetic diversity determination. PCR products sequenced. Phylogenetic analysis was performed, haplotype and nucleotide diversity was determined. The result for this study revealed that the prevalence of Fasciola based on liver and coprological examination was 34.78% (112/322) and 14.91% (48/322), respectively. Morphologically, 261/389, 61/389, and 67/389 were provisionally identified as F. gigantica, F. hepatica, and intermediate, respectively. Upon PCR, all provisionally identified Fasciola species were confirmed to be F. gigantica based on pepck gene marker. Ten fluke samples were amplified with the pold gene, and sequenced, on in silico digestion with Alu 1 enzyme; these showed 3 fragments of F. gigantica. Twelve fluke samples were amplified with both cox1 and nad1 markers and showed gene fragments of 438 and 535 base pairs, respectively. The PCR products were Sanger sequenced. In this study, 5 and 12 haplotypes for cox 1 and nad 1 genes, respectively were obtained from 12 sequences. The haplotype and nucleotide diversity were Hd 0.833 and 1.000, and Pi 0.00416 and 0.02202 for cox 1 and nad 1, respectively. The result suggests high genetic diversity in the study area and that the population of Fasciola is undergoing different selective pressures affecting survival and reproduction. This may cause a future increase in the Fasciola population, hence presenting a big challenge in the cattle population.