Fish egg disinfectant can eliminate VHS

A disinfection solution currently used for salmon eggs can prevent transmission of the virus that causes viral hemorrhagic septicemia (VHS) in other hatchery-reared fish eggs.

VHS is one of the most dangerous viral diseases of fish, and it has killed thousands of fish over the last few years in the US.

The disease causes internal bleeding in fish, and although in the family of viruses that includes rabies, is not harmful to humans. Thus far, the virus has been found in more than 25 species of fish in Lakes Michigan, Huron, Erie, St. Clair, Superior and Ontario, as well as the Saint Lawrence River and inland lakes in New York, Michigan and Wisconsin.

Effective disinfection methods are critically important to natural resource agencies that collect eggs from wild fish stocks and private aquaculture because the spread of the virus to a fish hatchery could be devastating, said Mark Gaikowski, a US Geological Survey (USGS) researcher who led the USGS and US Fish and Wildlife Service (USFWS) research team.

''If VHS virus is introduced into the aquaculture industry, it could lead to trade restrictions, as well as direct economic losses from the disease,'' Gaikowski noted.

USGS and USFWS researchers tested the effectiveness of using iodophor disinfection in walleye and northern pike eggs and found that it eliminated active virus from fertilised eggs. Iodophor disinfectant solutions contain iodine formulated for use on fish eggs. The researchers also found that although some of the disinfection treatments reduced hatch, iodophor treatment at 90 minutes after fertilisation occurred did not alter egg hatch or fry development.

Experts fear the disease could potentially spread from the Great Lakes into new populations of native fish in the 31 states of the Mississippi River basin. Regulatory agencies in the US and Canada have already placed restrictions on the movement of fish or fish products that could pose a risk for the spread of VHS virus to regions outside of the known geographic range.