Viral problems of Tilapia fish in Egypt

Abstract

Recently, Egyptian tilapia culture has suffered from mass mortalities (up to 70%). NNV and TiLV were of particular interest in the investigation of current mass mortalities in tilapia because TiLV and VNN can both infect tilapia and share various clinical symptoms, including nervous manifestations and ophthalmic manifestations similar to what was reported in the current outbreaks. Therefore, the development and validation of the synthetic positive control for TiLV and NNV was critical for the investigation of mass mortality causes in cultured tilapia. The design allowed the amplification of 605 nucleotides of the NNV RNA 2 and 484 nucleotides of segment 9 from TiLV using reference primers. Clinically infected tilapia fries exhibit skin darkening, spiraling along their axis were sampled from three hatcheries from Kafr El Sheikh and El Beheira governorate suffering from mass mortalities. Seven brood stocks from El Beheira were also collected. Samples were subjected to molecular detection by RT-PCR using specific reference primers, sequencing and phylogenetic analysis, electron microscopic examination and Kock's postulate for disease replication. The obtained results can be summarized as: 1- TiLV RNA was not detected in any of the extracts tested using RT-PCR.