ABSTRACT-The efficacy of inactivated betanodavirus as a vaccine against viral nervous necrosis (VNN) was evaluated using juvenile sevenband grouper Epinephelus septemfasciatus.Fish were intraperitoneally injected once with formalin-inactivated redspotted grouper nervous necrosis virus (RGNNV). Virus-neutralizing antibodies were detected in the vaccinated fish from Day 10 to the end of the experimental period (Day 160), showing 1: 2,000 or higher mean antibody titers from Day 21 to Day 77. The vaccinated and unvaccinated control fish were challenged by intramuscular injection with the homologous virus at 14, 35 and 74 days post-vaccination.The vaccinated fish showed significantly lower mortalities at any challenges than the control fish, with the RPS (relative percent survival) values 67 or higher. A field trial, in which fish were exposed to natural infection in net pens, also resulted in higher survival rates in the vaccinated fish (RPS = 85) during the experi mental period of 9 weeks. This high induction of neutralizing antibodies and protection indicates the potential of the inactivated virus vaccine against VNN.
Aims: Loop‐mediated isothermal amplification (LAMP) is a novel method that amplifies DNA with high specificity and rapidity under isothermal conditions. In this study, using the LAMP method, a protocol for detecting Nocardia seriolae which is a causative agent of fish nocardiosis, was designed.
Methods and Results: A set of four primers, two inner and two outer, were designed based on the sequence of the 16S–23S ribosomal RNA internal transcribed spacer region of N. seriolae. Time and temperature conditions for detection of N. seriolae were optimized for 60 min at 65°C. Other fish pathogen was not amplified by this LAMP system. The detection of N. seriola using LAMP was found to be more sensitive than that by polymerase chain reaction.
Conclusions: LAMP is a highly sensitive and rapid diagnostic procedure for detection of N. seriolae.
Significance and Impact of the Study: LAMP is a useful diagnostic method for fish nocardiosis.
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