Phylogenetics and Pathology of Hydatid Disease in Slaughtered Buffaloes of North India

Hydatid disease is one of the neglected and challenging (for diagnosis as well as for treatment) parasitic diseases. Along with adverse effect on animal's health leading to production losses, hydatidosis is also associated with huge economic losses. The present study was envisaged with an aim to assess the phylogeny and pathological changes due to natural hydatid cysts in lungs and liver of slaughtered buffaloes in north India.

A total of 137 slaughtered buffaloes intended for human consumption were screened for the presence of cysts. The retrieved cysts were confirmed molecularly based on the amplification of mitochondrial cytochrome oxidase 1 gene (mtCO1), exhibiting a product size of approximately 446 bp. The samples collected from infected lungs and liver were subjected to histopathological examination.

The hydatid cysts were recorded in 25 (18.2%) animals. Phylogenetic analysis revealed the isolated strain to be closely related to Echinococcus granulosus sensu stricto (G1) genotype. The nucleotide diversity (π) obtained was 0.014685, whereas, Tajima's D was negative (- 2.796053), which indicated purifying selection or recent population expansion. Histopathologically, in the infected lungs, fibrosis and inflammatory reaction comprising of mononuclear cells and fibroblasts around the thick coat of granulation tissue were observed. Marked calcified masses and necrosis were also observed in the calcified cysts. However, in case of infected livers, Kupffer cell hyperplasia, degeneration of hepatocytes, fibrosis and inflammatory cells were most commonly observed around the hydatid cysts.

The findings of the present study are of significant veterinary and medical importance owing to economic and public health impact of G1 genotype of E. granulosus.