Identification of Risk Factors for WSSV (White Spot Syndrome Virus) Infection in Shrimp (Penaeus monodon) Farms of Khulna and Bagerhat Districts

Abstract

In shrimp culture, various diseases, particularly white spot syndrome virus (WSSV), have emerged as a serious constraint to shrimp culture in Bangladesh. In this study, an initiative was taken to assess the risk factors for WSSV outbreaks, under which 72 farms were investigated in four upazilas of Bagerhat (Kochua, Rampal, and Fakirhat) and Khulna (Paikgacha) during 2010–2011. The major scenario depicted improved traditional culture methods with a stocking density of 15,000–20,000/ha for Bagda shrimp. The color of the soil of most of the ghers in the study area was found to be black. Water quality parameters, viz., temperature, dissolved oxygen, salinity, pH, ammonia, and alkalinity, ranged from 20.7–34.7°C, 3–8.7 mg/L, 1–15 ppt, 7–10, 0.3–1.9 mg/L, and 17.1–136 mg/L, respectively. Water depth in most of the ghers was found to be within the range of 0.45–1.8 m. PCR tests were carried out to confirm WSSV infection. About 20 factors were considered for assessing their association with WSSV outbreaks. The study revealed significant correlations with some factors, such as accessibility of cattle (r = 0.630, p ≤ .01) and linkage with other ghers (r = 0.754, p ≤ .01) within a cluster, based on Spearman's rho correlation coefficient test. Pearson's correlation coefficient showed that salinity had a significant negative correlation with the risk of WSSV infection (r = −0.727, p ≤ .01), followed by temperature (r = 0.624, p ≤ .01) and average depth (r = −0.618, p ≤ .01). However, feeding kept 30.6% of farms away from outbreaks, followed by sludge removal (26.39% of farms). On the contrary, the use of river water directly in the ghers caused a 38.9% risk of being attacked, whereas the corresponding risks were absolutely nil and 1.4% for underground water and rainwater, respectively. Therefore, ensuring proper gher management practices, using virus-free PL, building awareness at the farmer level, and developing community-based farm management can act as preventive measures to reduce the risk of WSSV infection.