Dr Naunain Mehmood (Sassari / IT; Sargodha / PK), Dr. Hira Muqaddas (Multan / PK), Dr. Muhammad Irfan Ullah (Sargodha / PK)
Abstract text
Introduction
Pakistan is a neglected endemic focus for Echinococcus granulosus sensu lato, a zoonotic parasite species complex with the ability to infect wide spectrum of hosts. Wide gaps exist in literature for etiological agents of cystic echinococcosis (CE) involved in epidemiological manifestation of this disease.
Objectives
The study explored main transmission routes of this disease through molecular characterization of hydatid cyst isolates.
Materials & methods
The hydatid cysts were collected from the seven major cities, encompassing four provinces, of Pakistan. Molecular characterization of the isolates obtained from sheep (n = 35), goats (n = 26), cattle (n = 30) and buffalo (n = 30) was based on partial mitochondrial nad1 gene. Additionally, computation of different genetic diversity indices such as number of haplotypes (hn), nucleotide diversity (nd) and haplotype diversity (hd) was carried out. The four subpopulations of E. granulosus were also evaluated for neutrality indices and estimation of genetic differentiation and degree of gene flow by employing a pairwise fixation index (Fst).
Results
Two strains of E. granulosus sensu stricto, G1/G3, and their haplotypes (n = 9) were observed to be cycling in sympatry in the domestic ungulate populations. G3 genotype had higher prevalence (66.94%) in the hosts compared to G1 genotype (33.06%) which was not surprising, considering the large buffalo population in Pakistan. Elucidating local transmission patterns of E. granulosus sensu stricto, buffalo-dog cycle emerged as one of the dominant causes of G3 dispersal. Population diversity indices had overall moderate values of haplotype diversity (0.6285 ± 0.038) coupled with low nucleotide diversity (0.00271 ± 0.0002). Population demographics and genetic variability indices suggested expanding parasitic population in multiple host spectrum.
Conclusion
It was demonstrated that the E. granulosus s.s. population in Pakistan was highly differentiated from the other regions of the world. Furthermore, large population of buffaloes in this region and stronger affinity of G3 for this host reflect heterogeneity in host specificity and adaptability to local environmental conditions making buffalo-dog cycle as one of the major transmission routes in CE epidemic in Pakistan. Following other regional studies, where sheep-dog cycle is considered as the major source of disease, might not fit the epidemiological situation in South Asia.