Identity of Fasciola spp. in sheep in Egypt.

BACKGROUND: In Egypt, liver flukes, Fasciola spp. (Digenea: Fasciolidae), have a serious impact on the farming industry and public health. Both Fasciola hepatica and Fasciola gigantica are known to occur in cattle, providing the opportunity for genetic recombination. Little is known on the identity and genetic variability of Fasciola populations in sheep.

METHODS: This study was performed to determine the prevalence of liver flukes in sheep in Menofia Province as a representative area of the delta region in Egypt, as measured by postmortem examination of slaughtered animals at three abattoirs. The identity and genetic variability of Fasciola spp. in slaughtered animals were determined by PCR-sequence analysis of the nuclear ribosomal internal transcribed spacer 1 (ITS1) and the mitochondrial NADH dehydrogenase subunit 1 (nad1) genes.

RESULTS: Physical inspection of the liver indicated that 302 of 2058 (14.7%) slaughtered sheep were infected with Fasciola spp. Sequence analysis of the ITS1 and nad1 genes of liver flukes from 17 animals revealed that 11 animals were infected with F. hepatica, four with F. gigantica, and two with both species. Seventy eight of 103 flukes genetically characterized from these animals were F. hepatica, 23 were F. gigantica, and two had ITS1 sequences identical to F. hepatica but nad1 sequences identical to F. gigantica. nad1 sequences of Egyptian isolates of F. gigantica showed pronounced differences from those in the GenBank database. Egyptian F. gigantica haplotypes formed haplogroup D, which clustered in a sister clade with haplogroups A, B and C circulating in Asia, indicating the existence of geographic isolation in the species.

CONCLUSIONS: Both F. hepatica and F. gigantica are prevalent in sheep in Egypt and an introgressed form of the two occurs as the result of genetic recombination. In addition, a geographically isolated F. gigantica population is present in the country. The importance of these observations in epidemiology of fascioliasis needs to be examined in future studies.