A TaqMan real-time PCR assay for quantifying white spot syndrome virus (WSSV) infections in wild broodstock and hatchery-reared postlarvae of fleshy shrimp, Fenneropenaeus chinensis

In the present study, a highly sensitive and specific TaqMan real-time PCR was developed to quantify white spot syndrome virus (WSSV) infections in wild broodstock and hatchery-reared postlarvae of fleshy shrimp, Fenneropenaeus chinensis. A total of 159 individuals Of Wild F chinensis brooders from 3 locations were captured and 210 postlarvae (PL1-8) were obtained from seven commercial hatcheries in 2007 in South Korea. The WSSV infections in 3 broodstocks showed a wide range, from 0 to 2.28 x 10(6) (with a mean of 1.50 x 10(4)) copies ng(-1) of DNA. Out of 159 brooders assayed, 39 (24.5%) were negative and 120 (75.5%) were positive: 153 (96.2%) showed less than 100 copies (mean 10.2 copies). 111 (69.8%) showed less than 10 copies and only 6 individuals (3.8%) showed high infections with a range of 2.36 x 10(2) to 2.28 x 10(6) copies ng(-1) of DNA. In 210 postlarvae, a range of 2.6 to 713.6 (with, mean of 220) copies g(-1) of DNA was observed. The mean WSSV copy number in the postlarvae was 7.9 x 10(5), which was equivalent to 8.5 x 10(5) copies mg(-1) of postlarvae weight. A total of 87.1% of postlarvae were WSSV positive and except for two hatcheries (H-4 and H-7) the postlarvae of all the other five hatcheries were positive. Even postlarvae from the same hatchery, especially of hatcheries H-4 and H-5, showed a wide range of WSSV infection resulting in higher infections than other hatcheries. There were 34.3% of the postlarvae assayed in the present study that showed very low infection, with less than 10 copies ng(-1) of DNA. Based on our results, it is recommended to pre-screen broodstock or larvae for selective breeding, stocking in production systems or stock enhancement. (c) 2008 Elsevier B.V. All rights reserved.