First report of Mud crab Reovirus (MCRV) outbreak in cultured Scylla serrata in India

Abstract

Reovirus is one of the most virulent pathogen found in mud crab Scylla serrata. The current study is the first reported incidence of a major outbreak of Mud crab Reovirus (MCRV) in the culture of S. serrata in Tamilnadu, South-east coast of India. The outbreak in the culture resulted in 100% mortality of the crabs within the culture period of 25 days resulting in a huge economic loss. The moribund crabs were observed to have discoloration of carapace, drastic growth retardation and loose gills. Histopathological studies confirmed the presence of atrophied hepatopancreas, basophilic and eosinophilic inclusions in the hepatopancreatic tubules of the infected crab. The TEM study revealed icosahedral, non-enveloped reoviral particles with diameter of 70 nm which were arranged in crystalline form and in parallel rows in the cytoplasm of the hepatopancreatic tubular epithelial cells. The MCRV infection was confirmed by RT-PCR in dead and moribund crabs. The experimental study of the ingestion transmission showed 100% mortality of crabs in 45 days. The present study shows the importance of monitoring the incidence and prevalence of MCRV in crab culture to minimize its spread in India.