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Diseases of Aquatic Organisms

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DAO 54:97-104 (2003)  -  doi:10.3354/dao054097

Relationship between white spot syndrome virus and indicators of quality in Penaeus monodon postlarvae in Karnataka, India

F. Corsin1, P. C. Thakur2, P. A. Padiyar2, M. Madhusudhan2, J. F. Turnbull1, C. V. Mohan2, N. V. Hao3, K. L. Morgan4,*

1Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, Scotland, United Kingdom
2Fish Pathology Laboratory, Department of Aquaculture, College of Fisheries, UAS, Mangalore, India
3Research Institute for Aquaculture N.2, 116 Nguyen Dinh Chieu Street, Ho Chi Minh City, Vietnam
4Department of Veterinary Clinical Science and Animal Husbandry, The University of Liverpool, Leahurst, Chester High Road, Neston CH64 7TE, United Kingdom
*Corresponding author. Email:

ABSTRACT: White spot disease (WSD) is a viral disease of shrimp caused by white spot syndrome virus (WSSV). Stocking WSSV-infected seed has been implicated as a major risk factor for outbreaks of WSD. In addition, the quality of postlarvae batches has been proposed as a predictor for good crops. This paper describes the relationship between indicators of quality and WSSV in postlarvae (PL) of Penaeus monodon from Karnataka, India, over the period September 1999 to January 2000. Three outcome variables were considered: the WSSV status of the PL, as determined by PCR, and 2 subjective assessments of PL quality, namely the activity of the PL and the quality of the PL as determined by research assistants and farmers, respectively. Of the 73 batches of PL, 49.3% from a random sample of farms tested positive for WSSV. After adjusting for confounding, stocking earlier in the growing season and duration of transportation were the main risk factors for the presence of WSSV. The quality assessed by farmers and the PL activity assessed by research assistants showed only fair agreement (kappa 0.252) reaffirming the subjective nature of such techniques. The only variables consistently associated with either assessment of quality in univariate analysis were PL length, number per bag and salinity of the water in the delivery bags. After adjusting for confounding, no single variable was consistently associated with PL quality and activity. The research assistants¹ assessment of PL activity was also associated with the hatchery and a brown-orange hepatopancreas in univariate analysis. After adjusting for confounding, a brown-orange hepatopancreas was still significant and fitted into the model together with the salinity of the water in the PL bags. The farmers¹ assessment of quality was associated with PL length, date of stocking and duration of transportation in both univariate and multivariable analyses. There was no relationship between quality assessment and WSSV in PCR-positive PL.

KEY WORDS: White spot syndrome virus · Epidemiology · Risk-factors · Penaeus monodon · Postlarvae

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