Molecular detection of betanodavirus in orange-spotted grouper (Epinephelus coioides) broodstock maintained in recirculating aquaculture systems and sea cages
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Wild collected orange-spotted grouper were domesticated in Recirculating Aquaculture Systems (RAS) and sea cages for fish breeding. While breeding, viral nervous necrosis (VNN) infection was observed in both the systems after 18 months of domestication. Out of 50 domesticated broodfish used in the study, 11 (22%) fishes were found positive for VNN examined by reverse transcriptase polymerase chain reaction (RT-PCR) method. Quantitative real-time PCR (qPCR) study also confirmed the presence of VNN in the suspected fish, and detectable amount of virus copy number was observed in the brain, optic nerve, caudal fin, muscle, and gills. Analysis of the isolated viral gene sequence from the fish was closely related to the red-spotted grouper nervous necrosis virus (RGNNV) genotype and suggests that the isolates are probably endemic to Indian coast. The study also indicated that the sub-adults of orange-spotted grouper infected in the wild and remained as carrier during domestication and subsequently disease outbreak has occurred when water temperature was increased in culture environment. This is the first report on VNN in orange-spotted grouper broodstock from India. The results of the study illustrated that large population of the wild marine fishes are sub-clinically infected with betanodavirus and therefore, early detection of the disease should be adopted as best management practices in breeding for sustainable aquaculture development of the species.
KeywordsIndia Orange-spotted grouper Broodstock Betanodavirus RAS Cage
The authors would like to thank Mr. Loveson L. Edward for productive input during the study.
There are seven authors who have contributed to accomplish the work with various levels. Sekar Megarajan has major contribution in planning and execution of the work. Ritesh Ranjan, Biji Xavier, Narasimhulu Sadu, and Chinnibabu Bathina had involved in sample examinations and further lab activities. Shubhadeep Ghosh and Achamveettil Gopalakrishnan had involved in overall management of the research program.
The authors are grateful to the Director, ICAR-CMFRI, for providing financial support to carry out this work.
Compliance with ethical standards
Conflict of interest
This study was conducted under one of the institutional research project work under the major research area. Therefore, there is no separate fund allotted to carry out this particular research work. All the institutional research project work was funded by Indian Council of Agricultural Research, New Delhi. The authors declare that they have no conflict of interest.
Research involving animals
The study was carried out on vertebrate fish used our breeding program. During the study, samples were collected from both the dead and live fishes. When live fishes were used the fishes were properly anesthetized and then used for the sample collection and related research work. However, the established protocols for examining the dead and live fish by the institute were followed during the examination of the fish. Therefore, this article does not contain any studies that are against to ethics.
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