Prevalence of Infectious Spleen and Kidney Necrosis Virus (ISKNV), Nervous Necrosis Virus (NNV) and Ectoparasites in Juvenile Epinephelus spp. Farmed in Aceh, Indonesia

Abstract

A cross-sectional survey was used to estimate the prevalence of infections with the Infectious spleen and kidney necrosis virus (ISKNV, Megalocytivirus), nervous necrosis virus (NNV, Betanodavirus), and infestations with ectoparasites during the rainy season in juvenile grouper (Epinephelus spp.) farmed in Aceh, Indonesia. The survey was intended to detect aquatic pathogens present at 10% prevalence with 95% confidence, assuming 100% sensitivity and specificity using a sample size of 30 for each diagnostic test. Eight populations of grouper from seven farms were sampled. Additional targeted sampling was conducted for populations experiencing high mortality. Infection with NNV was detected at all farms with seven of the eight populations being positive. The apparent prevalence for NNV ranged from 0% (95% CI: 0–12) to 73% (95% CI: 54–88). All of the fish tested from the targeted samples (Populations 9 and 10) were positive for NNV and all had vacuolation of the brain and retina consistent with viral nervous necrosis (VNN). Coinfections with ISKNV were detected in five populations, with the highest apparent prevalence being 13% (95% CI: 4–31%). Trichodina sp., Cryptocaryon irritans and Gyrodactylus sp. were detected at three farms, with 66% to 100% of fish being infested. Hybrid grouper sourced from a hatchery were 5.4 and 24.9 times more likely to have a NNV infection and a higher parasite load compared to orange-spotted grouper collected from the wild (p < 0.001). This study found that VNN remains a high-impact disease in grouper nurseries in Aceh, Indonesia.

Molecular evidence for homologous strains of infectious spleen and kidney necrosis virus (ISKNV) genotype I infecting inland freshwater cultured Asian sea bass (Lates calcarifer) in Thailand

“…ISKNV was also identi ed from various marine sh species in other Southeast Asian countries including Indonesia, Vietnam, Malaysia, and Singapore [11,23,39,46]. Most of the ISKNV found in these countries were genotype I, similar to our study, which indicated the widespread of this ISKNV genotype in Southeast Asia.…”

First report of infectious spleen and kidney necrosis virus in Nile tilapia in Brazil

“…The scale bar represents the nucleotide substitution per site associated with mortality in farmed barramundi (Dong et al, 2017), bluegill sunfish (Liu et al, 2019), Epinepheleus spp. (Sah Putra et al, 2020), mandarin fish (He et al, 2000), Murray cod (Go et al, 2006), pearl giant grouper (Huang et al, 2020) and ornamental fish species (Jung-Schroers et al, 2016;Tanaka et al, 2014 ). Therefore, ISKNV is considered as an emerging pathogen in both marine and freshwater aquaculture in many countries.…”

Megalocytiviruses in ornamental fish: A review

“…In another study in the same region, two-step PCR showed the percentage of ISKNV-like viruses detected in different seasons (22.1% winter, 27.8% summer, 34.0% autumn, and 17.0% spring) and proved that water temperature is a key condition for ISKNV outbreaks [ 16 ]. In other regions, such as Malaysia and Indonesia, Megalocytivirus have been observed in water temperatures ranging from 28°C to 32°C annually [ 85 ], with the highest mortality occurring at 27°C [ 87 ].…”