Genetic variability and diversity of Echinococcus granulosus sensu lato in human isolates of Pakistan based on cox1 mt-DNA sequences (366bp)

Cystic echinococcosis (CE) is a cyclo-zoonotic disease endemic to Pakistan, however, phylogeography and etiology of Echinococcus granulosus from human host has remained unexplored so far. The current study was carried out to estimate population structure and appraise the genetic variability of E. granulosus in two major provinces of Pakistan, Sindh and Punjab. 94 isolates were subjected to sequence analysis from histopathologically confirmed CE patients using a fragment of mitochondrial cytochrome c oxidase subunit 1 gene (cox1; 366bp). Three genotypes of E. granulosus sensu lato, G1 (57.44%), G3 (41.48%) and G6 (1.06%), were inferred to exist in human patients. Molecular diversity indices for E. granulosus sensu stricto manifested the presence of 14 haplotypes among the regional populations forming distinct clades with sheep (G1) and buffalo (G3) strains. The haplotype network displayed a double clustered star like feature with PK-H1c (37.63%) and PK-H9c (32.25%) as most dominant haplotypes displaying low genetic differentiation between the two geographic regions. Neutrality indices (Tajima's D and Fu's Fs) were negative for all populations indicating population expansion across Pakistan. The sympatric presence of G1 and G3 genotypes among humans in endemic focus of Pakistan confirms the zoonotic potential of E. granulosus s.s. with special emphasis on the G3 strain which emerged as a dominant cause of CE in humans compared to other global studies, where only G1 is linked to the majority of CE cases. Data from this study will prove to be a keystone for devising robust regional control strategies for human hydatidosis and investigating potential pathogenicity of E. granulosus s.l. haplotypes and their clinical manifestations in Pakistan.