Abstract
Fasciolosis, caused by Fasciola hepatica and Fasciola gigantica, is a globally significant parasitic disease affecting livestock and humans. Both species exist in South Africa, however, information on their geographical distribution and genetic diversity is limited. This study investigated the genetic diversity and phylogenetic relationships of Fasciola species in South Africa using Pepck, COI and ITS markers. Two hundred and seven Fasciola spp. specimens analysed in this study showed that 74.4% of isolates identified as F. hepatica and 25.6% as F. gigantica based on the Pepck gene. The geographical distribution revealed that F. hepatica occurred in all surveyed provinces but was dominant in the temperate zones of South Africa. Fasciola gigantica was confined to subtropical zones, with co-occurrence observed in Limpopo, Mpumalanga, and KwaZulu-Natal provinces. The COI and ITS genes in both Fasciola species generated fourteen and eight haplotypes respectively, with low to moderate haplotype diversity (Hd = 0.287 - 0.509 for COI and 0.056 - 0.239 for ITS) and low nucleotide diversity (Pi = 0.00085 - 0.00284 for COI and 0.00024 - 0.00034 for ITS), suggesting recent population diversification between the two species. The study samples yielded six haplotypes based on COI, with three haplotypes comprising most samples i.e. Hap-1 (F. gigantica) and Hap-5 and Hap-6 (F. hepatica). With ITS, two haplotypes represented most samples, i.e. Hap-1 (F. gigantica) and Hap-3 (F. hepatica). There was no observed unique distribution of haplotypes based on provinces or agro-ecological climatic zones for both markers. Phylogenetic analysis of both COI and ITS genes confirmed the grouping of the haplotypes and reiterated their relatedness. However, one isolate identified as F. gigantica in COI and with F. hepatica in ITS based on BLAST and further formed haplotypes with F. gigantica and F. hepatica haplogroups for COI and ITS, respectively. This suspected hybrid Fasciola form was from an animal with a mixed infection. These findings highlight the complex genetic structure of Fasciola spp. populations in South Africa and provide new insights into their epidemiology, with implications for targeted control strategies and further investigation of cryptic/hybrid lineages.