Efficacy of Whole Cell Inactivated Vibrio harveyi Vaccine against Vibriosis in a Marine Red Hybrid Tilapia (Oreochromis niloticus × O. mossambicus) Model.

Nadirah Abu Nor,Mohd Noor Amal Azmai,Mohd Fuad Matori,Annas Salleh,Ina-Salwany Md Yasin,Farina Mustaffa-Kamal,Mohd Zamri-Saad

doi:10.3390/vaccines8040734

Abstract

Vibrio harveyi causes vibriosis in various commercial marine fish species. The infection leads to significant economic losses for aquaculture farms, and vaccination is an alternative approach for the prevention and control of fish diseases for aquaculture sustainability. This study describes the use of formalin-killed Vibrio harveyi (FKVh) strain Vh1 as a vaccine candidate to stimulate innate and adaptive immunities against vibriosis in a marine red hybrid tilapia model. Tilapia are fast growing; cheap; resistant to diseases; and tolerant to adverse environmental conditions of fresh water, brackish water, and marine water and because of these advantages, marine red hybrid tilapia is a suitable candidate as a model to study fish diseases and vaccinations against vibriosis. A total of 180 healthy red hybrid tilapias were gradually adapted to the marine environment before being divided into two groups, with 90 fish in each group and were kept in triplicate with 30 fish per tank. Group 1 was vaccinated intraperitoneally with 100 µL of FKVh on week 0, and a booster dose was similarly administered on week 2. Group 2 was similarly injected with PBS. Skin mucus, serum, and gut lavage were collected weekly for enzyme-linked immunosorbent assay (ELISA) and a lysozyme activity assay from a total of 30 fish of each group. On week 4, the remaining 60 fish of Groups 1 and 2 were challenged with 108 cfu/fish of live Vibrio harveyi. The clinical signs were monitored while the survival rate was recorded for 48 h post-challenge. Vaccination with FKVh resulted in a significantly (p < 0.05) higher rate of survival (87%) compared to the control (20%). The IgM antibody titer and lysozyme activities of Group 1 were significantly (p < 0.05) higher than the unvaccinated Groups 2 in most weeks throughout the experiment. Therefore, the intraperitoneal exposure of marine red hybrid tilapia to killed V. harveyi enhanced the resistance and antibody response of the fish against vibriosis.

Highlights

Vibriosis is a disease that is caused by Vibrio spp. and is a major disease of commercial marine fish [1])
Vibrio spp. are Gram-negative bacteria commonly isolated from different ecosystems as well as aquaculture farms [22])
Many studies have shown that various species of Vibrio could lead to a systemic bacterial infection known as vibriosis

Summary

Introduction

Vibriosis is a disease that is caused by Vibrio spp. and is a major disease of commercial marine fish [1]). The first confirmed vibriosis in fish was reported by [2], when an epizootic among. Vaccines 2020, 8, 734 migrating eels, Anguilla vulgaris caused by a bacterium called Bacillus anguillarum, was reported in 1817. Later in 1909, the bacterium that was responsible for disease outbreaks in A. anguilla in Sweden was isolated and identified as V. anguillarum [3]. More outbreaks associated with Vibrio spp. infections among wild fish such as saithe and cod were reported [4]. This disease started to catch serious attention when it became a threat to farmed fish, especially in the North America, Europe, and Japan. In Asia, Vibrio spp. was first reported to affect the yellowtail

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