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Diseases of Aquatic Organisms

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DAO 56:1-10 (2003)  -  doi:10.3354/dao056001

Detection of gill-associated virus (GAV) by in situ hybridization during acute and chronic infections of Penaeus monodon and P. esculentus

Kirsten M. Spann1,2, Russell J. McCulloch1, Jeff A. Cowley, Iain J. East1,3, Peter J. Walker1,*

1Cooperative Research Centre for Aquaculture, CSIRO Livestock Industries, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Queensland 4067, Australia
2Present address: Laboratory of Infectious Diseases, National Institutes of Allergy and Infectious Diseases, Bethesda, Maryland 20892-0720, USA
3Present address: Office of the Chief Veterinary Officer, Agriculture Fisheries and Forestry Australia, GPO Box 858, Canberra, ACT 2601, Australia
*Corresponding author. Email:

ABSTRACT: Chronic and acute gill-associated virus (GAV) infections were examined by in situ hybridization (ISH) using a DNA probe targeting a 779 nucleotide region of the ORF1b-gene. Chronic GAV infections were observed in healthy Penaeus monodon collected from farms and healthy P. esculentus surviving experimental infection. During chronic-phase infections in both species, GAV was detected only in partitioned foci of cells with hypertrophied nuclei (spheroids) within the lymphoid organ. Acute-phase infections were observed in moribund P. monodon and P. esculentus infected experimentally with a high dose of GAV, and in moribund P. monodon collected from farms during outbreaks of disease. During acute experimental infections in P. monodon, ISH detected GAV throughout the lymphoid organ, in gills and in connective tissues throughout the cephalothorax. In moribund P. monodon collected from natural outbreaks of disease, GAV was also detected in the gills and in connective tissues of the cephalothorax, but the distribution of virus within the lymphoid organ varied. In acutely infected P. esculentus, GAV was detected in connective tissues, but was restricted to the inner stromal matrix cells and endothelial cells of intact lymphoid organ tubules. The tissue distribution of GAV identified by ISH suggests that shrimp are able to control and maintain chronic asymptomatic infection by a process involving lymphoid organ spheroids. Acute phase infections and the development of disease appear to be dose-related and involve the systemic distribution of virus in connective tissues throughout the cephalothorax.

KEY WORDS: Penaeid shrimp · GAV · DNA probe · In situ hybridization

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