Histopathological findings on innate responses of white spot disease positive Penaeus monodon (Fabricius) under semi‐intensive culture.

Abstract

White spot disease (WSD) is caused by white spot syndrome virus (WSSV), which is a bacilliform, non‐occluded, enveloped, double‐stranded (ds) DNA virus and belongs to the family Nimaviridae and genus Whispovirus (Vlak et al. 2005). In recent years, intensive studies on the virus have been made, particularly with respect to its organization, morphogenesis, pathology and pathogenesis (Escobedo‐Bonilla et al. 2008). Shrimps, like other invertebrates, lack a true adaptive immune system but have developed effective mechanisms for detecting and eliminating pathogens, which depend primarily on innate immune system (Loker et al. 2004). Haemocytes constitute the first line of internal defence against invading microorganisms. They are crucial in the immune responses of crustaceans and are capable of cell agglutination, phagocytosis, encapsulation, nodule formation and mediation of cytotoxicity (Soderhall 1999; Johansson et al. 2000). These cells are also involved in synthesis, storage, activation and discharge of pro‐enzymes and substrates of the clotting, and prophenoloxidase (proPO) cascades. Apoptosis has been proposed as the main antiviral mechanisms in invertebrates (Rhee, Kim & Park 2002). A comprehensive review of shrimp humoral responses, binding between shrimp and viral structural proteins and intracellular responses was conducted by Flegel & Sritunyalucksana (2011). In recent years, much information has been generated on the immune response genes and proteins involved in WSSV pathogenesis (Maningas et al. 2008). Under experimental conditions, there are reports of shrimp innate immune responses in terms of dramatic decline in circular haemocytes, changes in haemocyte structure and failure of hemolymph clotting in response to WSSV (Sahul Hameed et al. 2006; Arts et al. 2007). In the present study, we report on innate defence responses in Penaeus monodon (Fabricius) with clinical WSD in a semi‐intensive culture system. This study was a part of a larger epidemiological study on WSD carried out in the shrimp farms of Karnataka, West coast of India (Thakur et al. 2002; Turnbull et al. 2005; Sahoo et al. 2010).