Recurrent outbreaks of viral nervous necrosis in intensively cultured barramundi (Lates calcarifer) due to horizontal transmission of betanodavirus and recommendations for disease control

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• 作者：Paul Hick^a ; Glenn Schipp^b ; Jerome Bosmans^c ; John Humphrey^b ; Richard Whittington^a ; ^{richard.whittington@sydney.edu.au" rel="nofollow}
• 关键词：Barramundi ; Betanodavirus ; Cross-sectional survey ; Viral nervous necrosis ; Lates calcarifer ; Transmission
• 刊名：Aquaculture
• 出版年：2011
• 出版时间：1 September 2011
• 年：2011
• 卷：319
• 期：1-2
• 页码：41-52
• 全文大小：712 K
• ISSN：S0044848611005163

文摘

Betanodavirus is a significant constraint to marine finfish aquaculture worldwide and the development of control strategies will depend on accurate data about mechanisms of infection. A repeated cross-sectional survey for betanodavirus infection using a real-time reverse transcriptase-polymerase chain reaction assay and virus isolation was conducted in barramundi (Lates calcarifer) at a hatchery in Australia to determine whether transmission occurred vertically from the broodstock or horizontally from the environment. Six consecutive production batches were studied in 2007–2008. Subclinical infection was detected in Batch 2007-1 with onset of infection after 26 d of age, reaching a true prevalence > 90.9% (lower 95% probability limit) by 40 d. Two days later an outbreak of VNN with 100% mortality occurred in 12 d old larvae in Batch 2007-2, due to infection with an identical betanodavirus, which was not detected in this batch 7 d previously. A point source epidemic initiated by horizontal transmission from the environment (probably seawater) to Batch 1 then Batch 2 was confirmed. Betanodavirus was not endemic in the hatchery and was probably not vertically transmitted because: (i) infection was not detected in the eggs or larvae of any batch; (ii) infection was not detected in 4 out of 6 batches; (iii) infection was not identified in 20 broodstock; iv) freedom from infection of life history stages was determined with a very high degree of confidence; v) similar data were derived from archival samples from a batch in 2005. The data suggested that outbreaks were initiated because of vulnerabilities in the water supply and spread because biosecurity measures failed. The age of fish appeared to be a major risk factor for susceptibility to disease.