Molecular and morphological characterisation of Echinococcus from food producing animals in India

In view of the medical, veterinary and economic importance of hydatid disease in India, our study aimed to determine the prevalence and genotypes of Echinococcus present in domestic livestock in India. Out of 21,861 animals examined, cattle were found with the highest prevalence of hydatid cysts (5.10%) followed by buffaloes (3.81%), pigs (0.87%) and sheep (0.075%). Phylogenetic analysis of the cytochrome oxidase-1 gene revealed that the buffalo strain or G3 genotype was the predominant genotype (29/46) in all species of livestock followed by the cattle strain or G5 genotype (9/46), the G1 genotype or the common sheep strain (6/46) and the G2 genotype or Tasmanian Sheep strain (2/46). The ability of the G3 (buffalo) and G5 (cattle) genotypes of Echinococcus granulosus to infect and produce fertile hydatid cysts in pigs was also demonstrated for the first time. Both morphological and molecular results support earlier studies suggesting that Echinococcus of buffalo origin is phenotypically and genetically similar to the sheep (G1) and Tasmanian Sheep (G2) strains of Echinococcus, which adds further evidence to support its recognition as one species, viz., E. granulosus sensu stricto. Our molecular, morphological and biological characteristics also support earlier studies suggesting that Echinococcus of cattle origin, designated the G5 genotype, should be recognised as a separate species, viz. Echinococcus ortleppi. Finally, the study reveals that the prevalence of hydatidosis in urban centres in India has been showing a consistently declining trend over the past few decades, possibly owing to economic development and improved government legislation of abattoirs.