Spontaneous white spot syndrome virus (WSSV) infection in mud crab (Scylla serrata Forskal 1775) fattening pens farm of south east coast of India

The white spot syndrome virus (WSSV) is one of the most serious diseases in the shrimp and crab farm. This virus disseminates very quickly and causes high mortality in culture pond, accompanied by great economic losses. Recently, high mortality of WSSV-infected mud crabs collected from M.G.R. Thittu, Cuddalore district, Tamil Nadu, south east coast of India during 2015 and 2016. A total of 283 samples collected from pens fattening ponds were tested for the presence of WSSV. Of these, a prevalence of 32.5% WSSV-infected mud crabs showed. Hence, the present study was carried to understand the reason for the mortality. Our examinations of crab mortality confirmed the possible infestation of white spot syndrome virus. The classical symptoms of white spot virus infections like white spots in the inner carapace and histopathological changes on gills like eosinophilic inclusion bodies and basophilic Cowdry type “A” inclusion bodies have been observed. Also, our examinations confirmed the infestation through molecular diagnosis and TEM visualization of hypertrophied cells with massive viral particles in the nucleus and cytoplasm of infected gills. In the experimental work, the fastest mortality was observed in the ingestion then in the waterborne mode of infection. The waterborne mode caused the 40% mortality on 90th days. The ingestion mode caused the 100% mortality on 90th days.