Taura Syndrome Virus

Taura syndrome virus (TSV) is a shrimp RNA virus that was first described in 1992 from aquacultured shrimp in Ecuador. Since the initial outbreak, Taura syndrome disease (TSD) has spread to most shrimp-producing countries, primarily through transfers of shrimp seed and broodstock for aquaculture purposes or in frozen shrimp food products. This nonenveloped, icosahedral, single-stranded RNA virus is classified as a member of the newly created family Dicistroviridae, but has not been assigned to a specific genus. TSV has a linear genome with two open reading frames, ORF1 and ORF2, encoding structural and nonstructural genes, respectively. The intergenic region between ORF1 and ORF2 contains a unique internal ribosomal entry site element (IRES) that is capable of driving expression of the capsid protein gene in a cap-independent manner. TSD has acute, transition, and chronic phases. The chronic phase, as well as cannibalism and unrestricted movement of contaminated stocks, contribute to TSD spread. There are multiple strains of the virus that seem to differ in virulence for different shrimp species. Diagnosis of TSD is performed by bioassay, histology, reverse transcriptase-polymerase chain reaction (RT-PCR), and real-time RT-PCR. Therapeutic methods for TSD control are lacking; however, preventive methods such as biosecurity and use of TSV-resistant lines of shrimp provide a measure of protection against disease.