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Genetic Reassortment between Endemic and Introduced Macrobrachium rosenbergii Nodaviruses in the Murray-Darling
Vincenzo A Costa1, Jemma L Geoghegan2,3, Edward C Holmes1
1Sydney Institute for Infectious Diseases, School of Medical Sciences, The University of Sydney, Sydney, NSW 2006, Australia.
Abstract:
Macrobrachium rosenbergii nodavirus (MrNV)-the aetiological agent of white tail disease-is a major limiting factor of crustacean aquaculture as it causes up to 100% mortality in M. rosenbergii larvae and juveniles. Despite the importance of MrNV, there have been few studies on the phylogenetic diversity and geographic range of this virus in Australian waterways. Here, we detected MrNV genomes in common carp (Cyprinus carpio) metatranscriptomes sampled at five freshwater sites across the Murray-Darling Basin (MDB), Australia. We identified genetic divergence of the RNA-dependent RNA polymerase gene between MrNV sequences identified in the northern and southern rivers of the MDB. Northern viruses exhibited strong phylogenetic clustering with MrNV from China, whereas the southern viruses were more closely related to MrNV from Australia. However, all five viruses were closely related in the capsid protein, indicative of genetic reassortment of the RNA1 and RNA2 segments between Australian and introduced MrNV. In addition, we identified Macrobrachium australiense in two of the five MrNV-positive libraries, suggesting that these species may be important reservoir hosts in the MDB. Overall, this study reports the first occurrence of MrNV outside of the Queensland region in Australia and provides evidence for genetic reassortment between endemic and introduced MrNV.
Insights
Macrobrachium rosenbergii nodavirus (MrNV), a cause of white tail disease, was detected in Australian freshwater fish. This study reveals genetic reassortment between introduced and endemic MrNV strains in the Murray-Darling Basin.
Area of Science:
- * Virology
- * Aquatic Animal Health
- * Molecular Epidemiology
Background:
- * Macrobrachium rosenbergii nodavirus (MrNV) causes significant mortality in prawn aquaculture, leading to white tail disease.
- * Limited data exists on the phylogenetic diversity and geographic distribution of MrNV in Australian aquatic ecosystems.
- * Previous research has primarily focused on MrNV in Queensland, Australia.
Purpose of the Study:
- * To investigate the presence and genetic diversity of MrNV in freshwater fish within the Murray-Darling Basin (MDB).
- * To determine the phylogenetic relationships of detected MrNV strains with known global and Australian isolates.
- * To identify potential reservoir hosts for MrNV in the MDB.
Main Methods:
- * Metatranscriptomic sequencing of common carp (Cyprinus carpio) samples from five freshwater sites in the MDB.
- * Bioinformatic analysis to detect and identify MrNV genomes.
- * Phylogenetic analysis of RNA-dependent RNA polymerase and capsid protein genes.
Main Results:
- * MrNV genomes were detected in common carp from five MDB freshwater sites, expanding its known range in Australia.
- * Genetic divergence was observed in the RNA-dependent RNA polymerase gene between northern and southern MDB MrNV isolates.
- * Northern isolates clustered with Chinese MrNV, while southern isolates were closer to Australian strains, suggesting reassortment.
- * Macrobrachium australiense was identified in MrNV-positive samples, indicating its potential role as a reservoir host.
Conclusions:
- * This study reports the first detection of MrNV outside Queensland, Australia, in the MDB.
- * Evidence of genetic reassortment between introduced and endemic MrNV strains was found.
- * Common carp and Macrobrachium australiense are identified as potential hosts and reservoirs for MrNV in the MDB.
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