Department of Aquaculture, Fisheries College and Research Institute, Thoothukudi-628008, India.
Abstracts of the papers presented at the 16th Annual Convention and International Symposium of Indian Virological Society on “Management of Vector-Borne Viruses” at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru-502324, Hyderabad, India, February 7–10, 2006.
White spot syndrome virus (WSSV) is one of the most important pathogens of shrimps in India. It has substantially damaged Indian shrimp farming industry in the last decade. Following infection, WSSV spreads rapidly in shrimp population causing 100% mortality in many cases. In order to understand prevalence of the disease in coastal Tamil Nadu, we carried out a survey of shrimp farms for 3 years from 2002 to 2004 covering 55 locations. Samples were regularly collected and analysed for the presence of WSSV by diagnostic PCR. The virus was noticed in 46.4% of the samples analysed. Prevalence of white spot disease was high during September, October, July and December (>50%). Presence of WSSV showed a low incidence (average of 34.2%) with a moderately increasing trend in the first crop between March to August. The prevalence of the virus was higher during September to December (average incidence 65.8%), which showed a marginally diminishing trend temporally. Incidence of WSSV was found to increase with an increase in days of culture (DOC) of the crop with 61.5% of samples testing positive to the virus in >120 DOC culture. Of the 93 positive samples, 32 were analysed for strain variability by tandem repeat (TR) analysis using custom designed primers targeting ORF 94 of the virus. The analysis showed that WSSV exhibits strain variability by variable number of tandem repeats in the ORF 94 ranging from 2 to 16. The strains with 9 TRs were the highest followed by those with 6 and 12 TRs.
