Diagnosis of white spot syndrome virus in farm crawfish in Anhui province and its epidemiological source

Abstract:

Abstract:［Objective］ The aims of this study were to find out the pathogen causing high mortality of the crawfish population in Anhui over the past years．To provide the strategy for controlling the spread of the disease，an investigation was conducted to trace the origin of the pathogen．［Methods］Crawfish samples were tested by nested PCR，to diagnose the White Spot Syndrome Virus (WSSV)．Healthy crawfish were inoculated with the supernatant of tissue homogenates．The viral suspension was purified using sucrose density gradients． The gill samples infected with purified virus were then subject to the transmission electron microscopy (TEM)．The possible sources，including pond water，feedstuff，crabs，water plants，were investigated．［Results］ Crawfish samples and commercial feeds exhibited all positive for WSSV． Challenge model on healthy crawfish recovered similar symptoms as the naturally infected ones on 7 to 9 days after inoculation． The viral particles were observed under TEM．［Conclusion］ Our findings indicated that WSSV was the causative agent that led to high mortality in the crawfish population in this area．These results demonstrated that the exotic viruses are derived from the regions where the frozen feeds were contaminated with WSSV-infected shell debris．