Pathological and microbiological findings from mortality of the Chinese giant salamander (Andrias davidianus).

The Chinese giant salamander, Andrias davidianus, is a nationally protected and cultured species in China. Recently, a severe epizootic occurred in cultured Chinese giant salamanders in Hubei, Hunan, Sichuan, Shaanxi, and Zhejiang provinces of China, causing substantial economic losses. The typical clinical signs of diseased larval animals were jaw and abdominal swelling and subcutaneous hemorrhaging. Diseased adult animals exhibited skin hemorrhages, ulceration of the hind limbs, and multiple hemorrhagic spots in the visceral organs. Histopathological observation indicated tissue necrosis and cytoplasmic inclusions in the spleen, liver and kidney, suggestive of viral disease. A viral agent was isolated from affected tissues in cell culture. The virus was determined to be pathogenic after experimental infection. Electron microscopy revealed iridovirus-like virions with a size of 140-180 nm in diameter inside the kidney of naturally infected animals and in cell culture. The major capsid protein (MCP) of the virus exhibited 98-99 % sequence identity to ranaviruses. Additionally, phylogenetic analysis indicated that the virus belonged to the genus Ranavirus. Comparative analysis of the MCP gene sequence with those of other viruses previously isolated from Chinese giant salamanders revealed that these isolates were highly similar, although a few variations were observed. The virus was preliminarily named Chinese giant salamander iridovirus (GSIV).