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Diseases of Aquatic Organisms

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DAO 71:11-17 (2006)  -  doi:10.3354/dao071011

Quantitative relationship of two viruses (MrNV and XSV) in white-tail disease of Macrobrachium rosenbergii

Huajun Zhang1, Jianmin Wang1, Junfa Yuan1, Lijuan Li1, Jianhong Zhang1, Jean-Robert Bonami2, Zhengli Shi1,*

1State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, 430071 Wuhan, China
2Pathogens and Immunity, UMR5119, ECOLAG, CNRS/UM2, Université Montpellier 2, Montpellier, France
*Corresponding author. Email:

ABSTRACT: Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) were purified from diseased freshwater prawns M. rosenbergii and used to infect healthy post-larvae (PL) by an immersion method. Three groups of prawns were challenged with various combined doses of MrNV and XSV. Signs of white-tail disease (WTD) were observed in Groups 1 and 2, which had been challenged with combinations containing relatively high proportions of MrNV and low proportions of XSV. By contrast there was little sign of WTD in Group 3, which had been challenged with a higher proportion of XSV than MrNV. A 2-step Taqman real-time RT-PCR was developed and applied to quantify viral copy numbers in each challenged PL. Results showed that genomic copies of both viruses were much higher in Groups 1 and 2 than they were in Group 3, indicating that MrNV plays a key role in WTD of M. rosenbergii. The linear correlation between MrNV and XSV genome copies in infected prawns demonstrated that XSV is a satellite virus, dependent on MrNV, but its role in pathogenicity of WTD remains unclear.

KEY WORDS: Macrobrachium rosenbergii · Nodavirus · Extra small virus · Real-time RT-PCR · White-tail disease

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