Vibrio is a gram-negative bacteria with a curved-rod shape (Henry et al. 1994). Common pathogenic Vibrio species include Vibrio harveyi, Vibrio anguillarum, and Vibrio paraheamolyticus, and are the most prevalent pathogens in China. Taking Vibrio anguillarum for example, it caused deadly hemorrhagic septicaemic disease in many marine and freshwater species, including Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), turbot (Psetta maxima), sea bream (Sparus aurata), Asian sea bass (Lates calcarifer), eel (Anguila japonica/sinica), ayu (Plecoglossus altivelis) and groupers (Epinephalus spp.) (Frans et al. 2011).
The entry pathway of Vibrio anguillarum is either dermal or oral. In most cases, the bacterium enters the fish through epithelial cells, sites of injuries or damaged mucous layer. Oral infection typically
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Comparing with antibiotics as one of treatments conducted currently, the vaccine was derived from the virulent US strain and has been shown to protect against both the US and China virulent strains (Hossain et al. 2014). Poobalane claimed that a recombinant vaccine for the S-layer protein of Aeromonas hydrophila is able to protect common carp against six virulent isolates of Aeromonas hydrophila (Poobalane et al. 2010). S-layer protein is the common antigen found on all the isolates at around 50 kDa, and recombinant protein technology was used to produce sufficient quantities of the S-layer protein to enable large-scale vaccine trials to examine the ability of this protein to elicit protection against a variety of different Aeromonas hydrophila isolates. Poobalane vaccine trials also provides enough vertification that S-layers are often associated with invasive systemic infection and the recombinant S-layer protein vaccine have a greater ability to protect fish against natural infections by Aeromonas hydrophila (Poobalane et al.