Detection of Tilapia parvovirus in farm reared tilapia in India and its isolation using fish cell lines

Abstract

Nile tilapia with clinical signs of haemorrhages on the lower jaw, abdominal region and fin bases, discoloration of gill and cloudy eye were obtained from grow-out ponds situated in different parts of India and screened for tilapia lake virus (TiLV) and tilapia parvovirus (TiPV) by RT-PCR and PCR, respectively. The results showed the infection caused by TiPV in tilapia collected from ponds. It was further confirmed by the primers specific to TiPV designed by different workers. Sequence analysis of 534 bp of genomic region of TiPV showed 100% similarity with the sequence of TiPV strain of Thailand. TiPV was found in different organs including eggs of infected fish and showed the possibility of systemic infection and vertical transmission. Snakehead kidney, snubnose pompano fin and tilapia heart cell lines were shown susceptibility to TiPV. The viral replication in cell lines was confirmed by PCR, TiPV specific cytopathic effect of Cowdry A inclusion bodies with clear halo surrounding them and infectivity experiment. The disease was reproduced in normal fish by IM route using viral inoculum from TiPV-infected fish or virus multiplied in susceptible cell lines to satisfy Koch’s postulates. The present report on the occurrence of TiPV in tilapia is the first time in India after China and Thailand.