white spot disease

International Common Names

• English: China virus disease; red disease (white spot disease); rod-shaped nuclear virus of Penaeus japonicus (RV-PJ) infection; SEMBV infection; shrimp explosive epidermal disease; white spot baculovirus infection; white spot disease of penaeid shrimp; white spot syndrome; white spot syndrome baculovirus complex of penaeid shrimp; whitespot disease

English acronym

• SEED
• systemic ectodermal and mesodermal baculovirus infection
• WSD

White spot syndrome virus (WSSV), the aetiological agent of white spot disease (WSD), is one of the most devastating viral pathogens of shrimp culture worldwide (Escobedo-Bonilla et al., 2008; Lightner 2011). The virus was first reported in Taiwan in 1992 (Chou et al. 1995) and rapidly spread around the world (Zwart et al. 2010). WSSV is one of the most damaging shrimp pathogens to date, inflicting loss of production of approximately 300,000 tons of shrimp or about 1 billion US$ annually (Stentiford et al. 2012).

Gross clinical signs of WSD are the appearance of white spots at the cephalothorax region of the shrimp cuticle due to abnormal deposition of calcium salts, rapid reduction in food consumption, lethargy, and reddening of appendages. In the field, WSSV-infected shrimp gather near the pond edge and display clinical signs 1 or 2 days before the first mortalities occur. Cumulative mortality may reach 100% within 10 days after the onset of disease (Chou et al., 1995; Karunasagar et al. 1997).

WSSV is highly pathogenic and very infectious to decapods; however, variation in pathogenicity among isolates from different geographical regions (Laramore & Scarpa 2009; Zwart et al. 2010) and cross-species passaging (Gusheinzed Waikhom et al. 2006) have been reported. The virus initially replicates in the nucleus of epithelium cells lining the stomach wall (Durand et al. 1997), gills (Rahman et al. 2008) and later spreads via the haemolymph causing WSSV pathology in tissues that are of ectodermal and mesodermal origin (Chang et al. 1996). Transmission of WSSV from one shrimp species to another occurs by feeding on infected animals, direct contact with WSSV-contaminated water or cohabitation with infected animals (Rajan et al. 2000). Although mortality may reach 100%, under favourable culture conditions, shrimp can harbour WSSV for a long period without showing clinical signs (Tsai et al. 1999).

White spot disease is on the list of diseases notifiable to the World Organisation for Animal Health (OIE). The distribution section contains data from OIE's WAHID database on disease occurrence. For further information on this disease from OIE, see the website: www.oie.int