Efficacy of the inactivated nervous necrosis virus vaccine against viral nervous necrosis in pond-reared orange-spotted grouper Epinephelus coioides
Share
Abstract
The field efficacy of the formalin-inactivated nervous necrosis virus (NNV) against viral nervous necrosis (VNN) in orange-spotted grouper (Epinephelus coioides) reared in floating net cages in earthen pond was investigated. Seroneutralization assay conducted on the sera of vaccinated fish exhibited the occurrence of neutralizing antibody titers from Day 30 (mean titer 1:1792±701) to Day 150 (1:704±351) with the highest titer observed at Day 60 (1:6656±3435) post-vaccination. Because mortality attributed to VNN was not encountered during the pond experiment, intramuscular challenges of vaccinated and unvaccinated (L-15 injected) fish with NNV (106.5 TCID50/fish) were conducted in indoor tanks at Day 30 (Mean body weight [MBW]: vaccinated [21±3.4 g]; unvaccinated [20.6±1 g) and Day 120 (MBW: vaccinated [178±27 g]; unvaccinated [176±19 g) postvaccination, respectively, to demonstrate the in vivo efficacy of the inactivated vaccine. Nil and 25 % mortality rate were obtained in vaccinated and control fish, respectively, challenged with NNV at Day 30 post-vaccination. On the contrary, nil mortality were obtained in both groups challenged with NNV at Day 120 post-vaccination. Although nil mortality was obtained in NNV-challenged unvaccinated fish, 30 % of the fish manifested dark coloration of the skin and abnormal swimming behavior that commenced and disappeared at Day 3 and Day 7 post-NNV challenge, respectively, suggesting an age/ weight-dependent resistance to the disease. Our current data illustrate that single vaccination with inactivated vaccine could mount the production of protective antibodies and concomitant conferment of protection against VNN in groupers especially during the early phase of grow-out culture in earthen ponds where they are highly susceptible to the disease.
Suggested Citation
Pakingking Jr., R. V., de Jesus-Ayson, E. G., & Dionela, C. (2021). Efficacy of the inactivated nervous necrosis virus vaccine against viral nervous necrosis in pond-reared orange-spotted grouper Epinephelus coioides. In F. A. Aya, L. D. de la Peña, N. D. Salayo, & E. A. Tendencia (Eds.), Proceedings of the International Workshop on the Promotion of Sustainable Aquaculture, Aquatic Animal Health, and Resource Enhancement in Southeast Asia (pp. 229–237). Tigbauan, Iloilo, Philippines: Aquaculture Department, Southeast Asian Fisheries Development Center.
Type
Conference paperISBN
9789719931102 (Print); 9789719931119 (PDF)
Except where otherwise noted, this item's license is described as Attribution-NonCommercial-ShareAlike 3.0 IGO
Related items
Showing items related by title, author, creator and subject.
-
Protective immunity against viral nervous necrosis (VNN) in brown-marbled grouper (Epinephelus fuscogutattus) following vaccination with inactivated betanodavirus
Pakingking, Rolando V., Jr.
; ; ; (Academic Press, 2010)
Viral nervous necrosis (VNN) caused by betanodaviruses has been recently implicated in serious mortalities of groupers in the grow-out culture system. A safe and effective vaccine against this disease is urgently needed. This study demonstrates that a single intramuscular vaccination with formalin-inactivated Philippine strain of piscine betanodavirus (genotype: redspotted grouper nervous necrosis virus; RGNNV) induces potent immune responses and substantial protective immunity against an intramuscular challenge with the homologous virus in brown-marbled grouper, Epinephelus fuscogutattus, a highly susceptible marine fish species to VNN. Seroneutralization assay conducted on sera of vaccinated fish revealed the occurrence of substantial neutralizing-antibody titers from Days 15 (mean titer 1:800) to 190 (1:400) with the highest titer observed at Day 60 post-vaccination (1:5120). When vaccinated fish were challenged with the homologous virus at Days 15, 30 and 75 post-vaccination, significantly higher survival rates were obtained in these fish compared with their corresponding controls (L-15 injected fish). Abrogation of virus multiplication in all vaccinated survivors was indicated by undetectable virus titers in the brains and kidneys paralleled by significantly high levels of neutralizing antibodies in the sera of these fish. Consecutively, replicates of vaccinated fish that survived betanodavirus challenge at Days 15 and 75 post-vaccination were maintained in flow-through aquaria and rechallenged with the homologous virus 3 and 5 months later, respectively. A significant drop in neutralizing-antibody titers of 3 and 8 folds, respectively, were observed in the sera of Days 15 and 75 post-vaccinated fish assayed before the virus rechallenge. Interestingly, reversion in the levels of neutralizing antibodies to significantly high levels (8–15 folds) were noted in these fish after the virus rechallenge. Taken together, our current data clearly demonstrate that a single administration of the inactivated Philippine strain of betanodavirus vaccine can effectively mount a specific anamnestic response and concomitant long-term protection against VNN in grouper at the grow-out culture system. -
Immunization regimen in Asian sea bass (Lates calcarifer) broodfish: A practical strategy to control vertical transmission of nervous necrosis virus during seed production
Pakingking, Rolando V., Jr.; ; ; (Elsevier, 2018-08)
Outbreaks of viral nervous necrosis (VNN) in Asian sea bass (Lates calcarifer) at the larval stages via vertical transmission of nervous necrosis virus (NNV) from asymptomatic broodfish remain as a major deterrent during seed production. A five-year study was conducted to produce NNV-specific-free sea bass broodfish reared in land-based tanks through an annual immunization regimen with the formalin-inactivated NNV. We primarily immunized (intraperitoneal injection) sea bass juveniles (5 g) and monitored the neutralizing antibody (Nab) titers in the sera of these fish at scheduled intervals post-immunization. Nab titers in the sera of immunized fish peaked at Month 2 (titer: 1:4480 ± 1185) but thereafter gradually declined and significantly dropped (1:260 ± 83) at Month 12 post-primary immunization. Booster immunization of these fish at Month 12 post-immunization led to abrupt increases in Nab titers in booster immunized (B-Im) fish at Month 1 (1:12800 ± 6704) but thereafter declined and dropped at Month 12 (1:480 ± 165) post-booster immunization. The annual booster injections with the inactivated vaccine or L-15 (Unimmunized [U-Im]) were consecutively conducted for 4 years until the fish became sexually mature. Mature fish from both groups were successively induced to spawn twice (1-month interval) via intramuscular injection with luteinizing hormone-releasing hormone analogue (LHRH-a; 100 µg/kg BW). NNV was not detected by RT-PCR in oocytes and milts, and spawned eggs of B-Im fish. In contrast, oocytes and milts, and spawned eggs of U-Im fish were NNV positive. Spawned eggs of B-Im broodfish exhibited Nab titers ranging from 1:192 ± 34 to 1:240 while such was not detected (<1:40) in eggs of U-Im fish. Taken together, current data clearly demonstrate that annual immunization regimen with inactivated NNV vaccine is a pragmatic approach for sustaining immunocompetent sea bass broodfish reared in land-based tanks and circumvent the risk of vertical transmission of NNV from asymptomatic broodfish to their offspring under stress of repetitive spawning. -
Viral nervous necrosis (VNN) as a critical infectious disease of orange-spotted grouper, Epinephelus coioides, in the Philippines
(Japan International Research Center for Agricultural Sciences, 2007)Orange-spotted grouper, Epinephelus coioides, is a valuable commodity in the Philippines. In 2001, mass mortality occurred in the grouper larvae at Aquaculture Department, Southeast Asian Fisheries Development Center (SEAFDEC/AQD) and the disease was identified as viral nervous necrosis (VNN). Since then, the disease has been observed every year and the grouper hatcheries have been devastated. In this paper, recent studies of VNN which were conducted at the SEAFDEC/AQD from 2001 to 2006 are reviewed. 1) Susceptibility to the VNN virus was tested among fish species that were cultured in mangrove brackish are. Five representative cultured fish species including orange-spotted grouper, Asian sea bass (Lates calcarifer), mangrove red snapper (Lutjanus argentimaculatus), milkfish (Chanos chanos) and rabbitfish (Siganus guttatus) were used in the test where the virus was intraperitoneally injected into the juveniles. Although low or no mortality occurred in the challenge test, histopathological changes were observed in the brain and retina where the virus was re-isolated. The results were the same among the species except for rabbitfish which had no evidence for the infection. It was verified that the virus has a wide host range. 2) To estimate the possible risk of viral spread by vertical transmission, virus distribution was determined in asymptomatic groupers including 7 broodstock and 17 juveniles with body weights ranging from 4 to 12 kg and 2 to 9 respectively. The virus was detected by PCR method. The highest detection rate was in the brain, and the virus was also detectable in other organs such as the gills, heart, spleen, kidney, blood, esophagus, stomach, intestine, liver, gonad, swim bladder and/or skin. 3) As a possible VNN vaccine, a DNA p;asmid encoding the capsid protein of the virus was evaluated. After the challenge, the mortalities between the native and DNA-injected fish appeared significantly different (P<0.05).
