Epizootology and pathology of bacterial infections in cultured shrimp Penaeus monodon Fabricius 1798 in West Bengal, India

Abstract

A severe epizootic of bacterial diseases affected a number of commercial penaeid farms in Contai, Soula, Balisai and Digha regions of East Midnapur District, West Bengal, India in 2004. Histological and scanning electron microscopy (SEM) examination of affected Penaeus monodon showed massive infections in the hepatopancreas and partly in gills, pleopods and on shell. The affected shrimps had symptoms of vibriosis, gill disease, shell disease, red discolouration due to hepatopancreatitis etc. Shrimps with bacterial infection showed significant host inflammatory response in the form of hemocytic infiltration, granulomatous reaction and nodule formation. Histopathological observations revealed necrosis of hepato-pancreatic cells, thickened basal lamina and subsequent granulomatous encapsulation of the invaded tubules. Scanning electron microscopic (SEM) studies on shell diseased shrimp epithelial cells revealed signs of pathology due to bacterial infection. The normal SEM architecture of shell was totally lost and the shell had irregular indentations due to degenerative process. A large number of bacteria, which remain attached to the granular core of damaged epithelium of diseased shrimps were visible.