Detection of scale drop disease virus from non‐destructive samples and ectoparasites of Asian sea bass, Lates calcarifer

Abstract

Scale drop disease virus (SDDV) is the causative agent of scale drop disease (SDD), a newly emerging disease of farmed Asian sea bass, Lates calcarifer in Singapore, Indonesia, Malaysia and Thailand (Gibson-Kueh et al., 2012; de Groof et al., 2015; Nurliyana et al., 2020; Senapin et al., 2019). SDDV is a double-stranded DNA virus, having an icosahedral shape (140-180 nm diameter), with a reported incomplete genome size of 124,244 bp (de Groof et al., 2015). The virus is currently classified as a novel Megalocytivirus, one of the five genera within the family Iridoviridae (de Groof et al., 2015). The major capsid protein encoding gene of SDDV had a ~64%-65% nucleotide identity to other members in the same genus including infectious spleen and kidney necrosis virus (ISKNV), red seabream iridovirus (RSIV) and turbot reddish body iridovirus (TBIV) and 73.28% identity to a newly identified

Genome Characterization and Phylogenetic Analysis of Scale Drop Disease Virus Isolated From Asian Seabass (<em>Lates calcarifer</em>)

“…Interestingly, sample 7 was obtained from fin tissue, which is generally considered to be a lower priority target organ for SDDV during the early stages of infection [43]. This aligns with a recent study by Charoenwai et al [17] which also detected SDDV in non-destructive samples like mucus and fin clips.…”

“…Tissues were preserved in RNAlater™ reagent (Thermo Fisher Scientific, Massachusetts, USA) and kept at -20 ˚C until use. Genomic DNA was extracted using a conventional phenol/chloroform method [17]. All fish samples were screened for SDDV infection using SDDV-specific semi-nested conventional PCR as described in [18] to confirm SDDV infection prior to sequencing.…”

Impact of transport conditions and underlying disease on post‐stocking survival of juvenile Lates calcarifer

“…However, with the increasing prevalence of SDDV, the disease is now reported in L. calcarifer up to 1.1 kg in Singapore, Malaysia, Thailand, and Indonesia (de Groof et al., 2015; Gibson‐Kueh, 2012; Nurliyana et al., 2020; Senapin et al., 2019). SDDV is commonly complicated by co‐infections with Vibrio harveyi , Flavobacterium columnare, Lates calcarifer herpesvirus, or ectoparasites such as Lernanthropus and Diplectanum species (Charoenwai et al., 2021; Domingos et al., 2021; Dong et al., 2017; Kerddee et al., 2020). Monogeneans and marine leeches are non‐host‐specific ectoparasites that produce large numbers of sticky eggs and are difficult to eradicate, with heavy infestations often associated with high mortalities in intensive aquaculture (Jahangiri et al., 2022; Kua et al., 2010; Ogawa, 2015).…”

Genetic characterizations, virulence, antimicrobial resistances and resistome analysis of vibrio spp. Isolated from farmed Asian sea bass (Lates Calcarifer) in Thailand

“…Between 2018 and 2021, 184 Asian sea bass samples were collected from 15 farms in Thailand's Krabi, Phuket, Phang-Nga, Satun, Samut-Songkhram, Phetchaburi, Chachoengsao, Rayong, and Chanthaburi provinces (Figure 1). The data on diseased fish from Chanthaburi was gathered from previous research (Charoenwai and SONTHI, 2021), while diseased and non-diseased fish from other provinces were retrieved and transported alive in the tank to the laboratory, where necropsy and bacterial isolation were performed on the same day the fish arrived. The fish selected in this study were diseased (with any clinical sign) or non-diseased (apparently healthy without clinical sign) Asian sea bass that culture in the brackish or marine water (> 5ppt), with no specific criteria for size, sex, or clinical sign.…”