Taura syndrome in Penaeus vannamei (Crustacea:Decapoda):gross signs, histopathology and ultrastructure

Abstract

Taura syndrome (TS) is a n economically important disease of Penaeus vannamei (Crustacea-Decapoda) that was first recognized in commercial penaeid shrimp farms located near the mouth of the Taura River in the Gulf of Guayaquil, Ecuador, in June 1992. The syndrome is now known from shrimp farms throughout the Gulf of Guayaquil, as well as from single or multiple farm sites in Peru, Colomb~a, Honduras, and Oahu, Hawaii, USA. Both toxic and infectious et~ologies for TS have been proposed, but TS appears to have a viral etiology due to a previously unrecognized agent now called Taura syndrome virus or TSV The disease has peracute and recovery [or chron~c) phases, which are grossly distinguishable. Peracute episodes of TS are the most common manifestation of TS and occur in juvenile shrimp (of 0.1 to 5.0 g ) within 14 to 40 d of stocking into grow-out ponds or tanks. Gross signs displayed by moribund shrimp with peracute TS include expansion of the red chromatophores giving the affected shrimp a pale reddish coloration and making the tail fan and pleopods distinctly red. Peracutely affected anlmals usually die d u r ~n g the process of molting. Those with peracute or acute TS that survive molting either recover or are chronically affected by TS and typically display multiple melamzed cuticular lesions suggestive of 'shell disease' Shrimp acutely affected with TS d ~splay a distinctive hstopathology that consists of multifocal areas of necrosis of the cuticular epithelium and subcutis (of the general cuticle, gills, appendages, foregut and hindgut), which are characterized by the presence of several to extremely numerous, variably sized eosinophilic to basophilic cytoplasmic inclusion bodies that give TS lesions a characteristic 'peppered' or 'buckshot' appearance, which is considered to be pathognomonic for TS. Transmission electron microscopy of affected cells shows these inclusion b o d ~e s to be composed of an amorphous, granular, electron-dense matrix in which are often embedded numerous needle-like crystals of presumed calc~um phosphate. The purpose of the present paper is to provide a definition of TS (based primarily on gross signs and histopathology supported by electron microscopy) as a basis for future studies on the dlsease