Isolation and Characterization of a Ranavirus Associated with Disease Outbreaks in Cultured Hybrid Grouper (♀ Tiger Grouper Epinephelus fuscoguttatus × ♂ Giant Grouper E. lanceolatus) in Guangxi, China

Abstract

An outbreak of suspected iridovirus disease in cultured hybrid grouper (♀Tiger Grouper Epinephelus fuscoguttatus × ♂ Giant Grouper Epinephelus lanceolatus) occurred in the Guangxi Province in July, 2018. In this study, grouper iridovirus Guangxi (SGIV‐Gx) was isolated from diseased hybrid grouper that were collected from Guangxi. Cytopathic effects were observed and identified in grouper spleen cells that were incubated with diseased tissue homogenates after 24 h, and the effects increased at 48 h postinfection. The transmission electron microscopy results showed that viral particles that were about 200 nm in diameter with hexagonal profiles were present in the cell cytoplasm of suspected virus‐infected cells. The presence of SGIV‐Gx (accession number: MK107821) was identified by polymerase chain reaction (PCR) and amplicon sequencing, which showed that this strain was most closely related to Singapore grouper iridovirus (AY521625.1). The detection of SGIV‐Gx infection was further supported by novel aptamer (Q2c)‐based detection technology. The effects of temperature and pH on viral infectivity were analyzed by using reverse transcription quantitative real‐time polymerase chain reaction (RT‐qPCR) and cell culture. The results indicated that SGIV‐Gx was resistant to exposure to pH levels 5, 7, and 7.5 for 1 h, but its infectivity was remarkably lower at pH levels 3 and 10 after 1 h. The analyses showed that SGIV‐Gx was stable for 1 h at 4°C and 25°C but was inactivated after 1 h at 40, 50, and 60°C.

Aptamer‐based high‐throughput screening model for medicinal plant drugs against SGIV

“…Singapore grouper iridovirus (SGIV) is a major pathogen that causes heavy economic losses to the grouper aquaculture (Xiao et al., 2019). Therefore, effective drugs for controlling SGIV infection are urgently needed.…”

Antiviral activity of Illicium verum Hook. f. extracts against grouper iridovirus infection

“…Since there are currently no licensed treatments available, grouper iridovirus poses a serious threat to the rapid development of grouper aquaculture in China (Li, Zhou, Ni, et al, ). For example, SGIV‐Gx outbreaks in cultured hybrid groupers ( E. fuscoguttatus ♀ × E. lanceolatus ♂) in Guangxi in July of 2018 caused large‐scale mortality and heavy economic losses (Xiao et al, ). Therefore, effective treatment for grouper iridovirus infection is urgently required.…”

Antiviral abilities of Curcuma kwangsiensis ingredients against grouper iridoviral infection in vitro and in vivo

“…The GS cell line was derived from grouper spleen and maintained at 28°C in Leibovitz's L15 medium (Gibco; Qin et al, ; Qin, Wu, Jia, Hegde, & Zhang, ). The grouper Iridovirus strain (SGIV‐Gx) used in this study was isolated from hybrid grouper ( E. fuscoguttatus ♀ × E. lanceolatus ♂) in Guangxi, which belong to genus Ranavirus (Xiao, Liu, Li, et al, ). SGIV‐Gx was purified using sucrose gradient ultracentrifugation and stored in TN buffer containing 0.01 M Tris‐HCl (pH 7.2) and 0.85% NaCl (Li et al, ).…”

“…aquaculture in China has exceeded 159,579 tons in 2018 (Xu, Wu, Guo, & Gao, ). However, the rapidly expanding scale of grouper aquaculture has resulted in the increasing outbreaks of fish viral diseases (Xiao, Liu, Li, et al, ; Yu, Liu, Wei, et al, ). Grouper Iridovirus is one of the most serious pathogens and usually causes great economic losses to grouper aquaculture all over the world.…”

“…Grouper Iridovirus is one of the most serious pathogens and usually causes great economic losses to grouper aquaculture all over the world. Grouper iridoviral infection could induce cytopathic effects (CPEs) in cultured grouper cells, where viral particles about 200 nm in diameter and with hexagonal profiles could be observed in the infected cell cytoplasm (Qin et al, ; Xiao, Liu, Li, et al, ). Infected groupers displayed typical clinical signs, including loss of appetite, enlargement of the liver and spleen tissues, and eventually lead to a large‐scale mortality in few days.…”