Macrobrachium rosenbergii nodavirus disease (white tail disease) in Australia

Abstract

The index case of white tail disease (WTD) is presented in adult broodstock prawns Macrobrachium rosenbergii from the Flinders River in western Queensland, Australia, in mid-2007. Histological examination revealed extensive myonecrosis with massive infiltration of myonuclei and some haemocytes. Juveniles from the same broodstock but not from 3 other families displayed white muscle lesions. Low-grade chronic mortalities approaching 100% over 1 yr occurred. Reverse transcriptase polymerase chain reactions (RT-PCR) were attempted for both M. rosenbergii nodavirus (MrNV) with 2 sets of primers and for the satellite virus, extrasmall virus (XSV). All 3 PCRs generated amplicons of the expected sizes. Basic local alignment search tool (BLAST) analyses of the 3 consensus sequences identified a 91% match with MrNV viral capsid protein gene, 96% match with MrNV RNA-directed RNA polymerase gene, and a 99% match with M. rosenbergii XSV capsid protein gene. The clinical signs, histopathological lesions and RT-PCR amplicons could be reproduced in M. rosenbergii inoculated with cell-free extracts fulfilling River's postulates. We conclude that this is an endemic strain of MrNV as the sequences are dissimilar to strains of MrNV circulating around Asia and the Americas. This case only poorly meets the Office International des Epizooties (OIE) case definition for WTD due to the age of the prawns involved and the nature of the inclusion bodies. Perhaps the OIE case definition needs broadening.

White Tail Disease of Freshwater Prawn, Macrobrachium rosenbergii

“…The disease was first reported in the French West Indies [1], later in China [13], India [20], Chinese Taipei [34], Thailand [37], Australia [11] and Malaysia [17].…”

Monoclonal antibodies against extra small virus show that it co-localizes with Macrobrachium rosenbergii nodavirus

“…Outbreaks of white tail disease (WTD) in hatcheryreared postlarvae (PL) of the giant river prawn Macrobrachium rosenbergii have occurred in many parts of the world including the West Indies (Arcier et al 1999), Taiwan (Tung et al 1999, Wang et al 2008), China , India (Sahul Hameed et al 2004), Thailand (Yoganandhan et al 2006), and Australia (Owens et al 2009). WTD is caused by Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) (Arcier et al 1999, is characterized by whitened abdominal muscle, and can cause almost complete losses of PL in hatcheries and nursery ponds within 5 d of gross signs first appearing (Arcier et al 1999).…”

“…The XSV genome is a singlestranded RNA 796 nucleo tides in length that encodes a 16−17 kDa capsid protein (CP). XSV is considered to be a satellite virus dependent on the MrNV RNA-dependent RNA polymerase for genome replication , Bonami et al 2005.Dot blot and in situ hybridization (Sri Widada et al 2003, Hsieh et al 2006, Wang et al 2008, RT-PCR (Sri Widada et al 2003, Sahul Hameed et al 2004, multiplexed RT-PCR (Yoganandhan et al 2005, Tripathy et al 2006, Owens et al 2009, real-time RT-PCR (Zhang et al 2006), and reverse transcription loop-mediated isothermal amplification (RT-LAMP) (Pillai et al 2006, Haridas et al 2010, Puthawibool et al 2010) have been developed to detect MrNV and/or XSV RNA. While highly specific and sensitive, all of these molecular detection methods are quite complicated and expensive and thus not practical for pond-side detection of these viruses.…”

Immunological-based assays for specific detection of shrimp viruses

“…WTD causes significant mortality in hatchery-and nursery-reared postlarvae [94] . The disease was first reported in Guadeloupe Island (French West Indies) in 1997 [95] and was later reported in China [96] , India [97] , Thailand [98] , Taiwan [99] and Australia [100] . MrNV is a nonenveloped, icosahedral virus with a diameter of 26-27 nm and a genome comprised of two pieces of positive-sense ssRNA.…”