Evaluation of the diagnostic assays detecting red sea bream iridovirus infection at different severity levels

• Published in: Journal of virological methods 2024-05, Vol.326, p.114901-114901, Article 114901
• Main Authors: Kim, Kyung-Ho, Kang, Gyoungsik, Woo, Won-Sik, Sohn, Min-Young, Son, Ha-Jeong, Kim, Ju-Won, Kong, Hee Jeong, Kim, Young-Ok, Park, Chan-Il
• Format: Article
• Language: English
• Subjects: 95% limit of detection; Diagnostic assays; PCR; Red sea bream iridovirus; WOAH
• ISSN: 0166-0934; 1879-0984
• DOI: 10.1016/j.jviromet.2024.114901

Red sea bream iridovirus (RSIV) is a highly contagious viral infection that affects various fish species and poses a significant threat to the global aquaculture industry. Thus, accurate and timely diagnosis is paramount for sustainable management of fish health. This study rigorously evaluated the diagnostic efficacy of various polymerase chain reaction (PCR) assays, focusing on those recommended by the World Organization for Animal Health (WOAH) and the assays newly proposed by WOAH's Aquatic Animals Health Standards Commission. Specifically, this study assessed conventional PCR, nested PCR, modified 1-F/1-R, and real-time PCR assays using a 95% limit of detection (LoD95%), as well as diagnostic sensitivity (DSe) and specificity (DSp) tests across different RSIV severity grades (G0−G4). In previous studies, the LoD95% for the 1-F/1-R and 4-F/4-R conventional assays were 225.81 and 328.7 copies/reaction, respectively. The modified 1-F/1-R exhibited a lower LoD95% of 51.32 copies/reaction. Notably, the nested PCR had an LoD95% of 11.23 copies/reaction, and the real-time PCR assay had an LoD95% of 12.02 copies/reaction. The DSe varied across RSIV severity grades, especially in the lower G0−G2 grades. The nested PCR and modified 1-F/1-R assays displayed the highest DSe, making them particularly useful for early-stage screening and detection of asymptomatic carriers. In addition, the PCR assays did not cross-react with any other aquatic pathogens except RSIV. Our findings significantly advanced the diagnostic capabilities of RSIVD by suggesting that nested PCR and modified 1-F/1-R assays are particularly promising for early detection. We propose their inclusion in future WOAH guidelines for a more comprehensive diagnostic framework. •This study evaluated the performance of several diagnostic assays based on RSIV severity.•The evaluated diagnostic assays showed significant differences in DSe at severity levels G0−G2 of RSIV.•The PCR (modified 1-F/1-R) and nested PCR assays for RSIV detection are useful for the detection of asymptomatic infected fish.