Systemic disease caused by an iridovirus‐like agent in cultured mandarinfish, Siniperca chuatsi (Basilewsky), in China

Mandarinfish, Siniperca chuatsi (Basilewsky), is an economically important fish in southern China.A disease in cultured mandarinfish resulted in significant economic losses in central Guangdong Province, China, from March to November 1994 -1997.In 1998, acute outbreaks of the disease caused up to 50% mortality among all farmed mandarinfish in Nanhai, Guangdong Province.The mortality of the affected farmed mandarinfish reached 100% within 7-10 days.The affected fish in the cultured ponds showed signs of anorexia, abnormal swimming along the side of the pond, light body pigmentation and pale gills.The most prominent features of the affected fish were petechial haemorrhages in the operculum, mandible, orbit around the eye, base of dorsal and ventral fins, caudal fin, and abdomen.The kidney was swollen, the spleen was enlarged, and the heart and liver were pale with petechial haemorrhages.These signs are similar to the disease in fish caused by iridovirus.Iridoviruses have been found in a wide variety of fish species and are now recognized as a pathogen causing systemic diseases in cultured fish (Langdon, Humphrey, Williams, Hyatt & Westbury 1986;