Survey on infection of two viruses in the wild mud crab (Scylla paramamosain) in Yangjiang, Guangdong province

Mud crab dcistrovirus-1(MCDV-1) and mud crab reovirus (MCRV) are of serious pathogenicity to the mud crab (Scylla paramamosain), which cause high mortality and great economic losses in the mud crab culture. A survey was carried out to determine the virus infection in the wild mud crab captured along Yangjiang coast from May to October in 2012. The viruses were detected by a duplex nested-PCR. The results showed that high infection rate of virus were observed in the wild mud crab (44.83%~100%) from May to October in 2012. The high rate of MCDV-1 infection appeared in June, August and September. The high rate of MCRV infection appeared in May, June, August and September. In May, July and October, single infection dominated (44.83%) in wild mud crabs; while in June, August and September, coinfection (82.76%) dominated. These results reveal that the peak epidemic months of two viruses are May-June and August-September. During these months, MCDV-1 and MCRV often jointly infect wild mud crab.