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SEAFDEC Develops Vaccine Against VNN

PHILIPPINES - A vaccine is being field tested against Viral Nervous Necrosis (VNN), a virus that causes one of the worlds most lethal fish diseases that wipes out entire stocks.

MalayaBusinessInsight reports that the Southeast Asian Fisheries Development Center (SEAFDEC) is currently developing a vaccine for VNN as, at present, there is no drug available to prevent the hard to control infection.

Talking to Malaya Business Insight, Dr Joebert D. Toledo, from the(SEAFDEC) Aquaculture Department, said: "The emergence of fish diseases caused by viruses, bacteria and other parasites is one of the downsides of the booming aquaculture industry."

While a vaccine for VNN is also being developed in Japan and Taiwan, the SEAFDEC vaccine is being tested in broodstock, or breeders, as an attempt to produce offspring that are free from VNN, explained Dr Rolando V. Pakingking Jr, a virologist at SEAFDEC’s Fish Health Section.

This is important because it is suspected that VNN outbreaks in the Philippines are caused by the transmission of the virus from VNN-positive broodstocks to their offspring, he told Malaya Business Insight.

The suspicion is based on the fact that the virus is already widespread in the marine environment as indicated by trash fish used as feed to breeders that test positive for the virus, he said.

Dr Pakingking’s research demonstrates that a single injection with a formalin-inactivated vaccine induces potent immune responses and substantial protective immunity among experimental sea bass, grouper and pompano exposed to the VNN virus.

The SEAFDEC vaccine gives protection to broodstock, or the parents, "to ensure you have VNN-free breeders," Dr Pakingking pointed out.

When the the formalin-inactivated vaccine was injected to infected fish – under experimental conditions – the vaccine produced protective antibodies effective against the VNN virus, with a 90 to 100 per cent survival, or protection, rate.

Tested in grouper which is more susceptible to the VNN virus, antibodies provided protection even up to six months, the usual time it takes to raise the fish until harvest. Positive results have been observed in ongoing experiments with pompano fish cage culture.

Concluding, Dr Pakingking said he could not tell when the vaccine would be commercially available as it is still under field trials at the SEAFDEC Igang Marine Fish Station in Guimaras.

the Fish Site Editor

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