Taura Syndrome Virus Disease in Farm-Reared Penaeus monodon in Thailand

Taura syndrome virus (TSV) has caused major economic losses to shrimp aquaculture throughout the world. TSV has been reported to infect a number of penaeid species as hosts. In this study, we reported the natural infection of TSV in farm-reared Penaeus monodon from eastern provinces of Thailand between June to September 2004. There were different degrees of disease outbreak severity. In some cases large number of shrimp died and caused great losses to farmers. However, in most cases only small number of shrimp died and the farmers could control the situation enough to raise the majority to marketable size. Diseased shrimp varied in size from aged 40-50 days (4 g) to 20 g. Infected shrimp was characterized by black cuticular lesions and loose shell. Histopathological changes in infected shrimp showed multifocal to extensive areas of necrosis in the sub-cuticular epithelium, connective tissue and adjacent striated muscle. Affected cells often displayed an increased cytoplasmic eosinophilia, nuclear pyknotic and karyorrhexis. In situ hybridization tests gave positive results with the tissues of shrimp collected from the TSV outbreaks. In addition to TSV infection, most moribund shrimp also had dual infections with microsporidians in the hepatopancreas and/or gregarines in the gut.