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

Tilapia parvovirus (TiPV) is an emerging viral pathogen and responsible for severe economic loss in tilapia culture production. Lethargic, cutaneous haemorrhages; ocular lesions; discolouration of gill and cloudy eye and exophthalmia are common symptoms of TiPV. The TiPV-suspected tilapia fish were collected from grow-out ponds situated in different parts of Tamil Nadu, India, and screened for TiPV by PCR. The results showed the presence of TiPV in disease-suspected fish which was further confirmed by PCR using different primer sets specific to different genomic regions of TiPV. Sequence analysis of 534 bp of genomic region of TiPV showed 100% similarity with the sequence of TiPV strain of Thailand and India. TiPV was found in different organs including eggs of infected fish and showed the possibility of systemic infection and vertical transmission. Snakehead kidney (CSK), snubnose pompano fin (SPF) and tilapia heart (TH) cell lines showed 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 intramuscular route using viral inoculum from TiPV-infected fish or virus multiplied in susceptible cell lines to satisfy Koch's postulates.