Viral hemorrhagic septicemia (VHS), a pathogen which has killed tens of thousands of fish in the US Great Lakes in recent years now risks spreading and affecting inland fish farming.
Last October, the United States Department of Agriculture (USDA) issued an emergency order to restrict the movement of live fish caught in the eight states that border the Great Lakes and two Canadian provinces.
The problem first came to the public eye when dead fish began washing up on beaches in Lake Ontario, Lake Erie and the St. Lawrence River in May 2006.
Commercially fished species such as lake whitefish, walleye and yellow perch are all believed to be susceptible to the virus, and it is now feared that the catfish industry, the largest sector of the US aquaculture industry, could be hit.
Scientists believe VHS virus has been present in the Great Lakes since 2003, when it may have originated from bilge water from sailing vessels.
A strain of the virus has had dire consequences for trout and other commercially farmed freshwater fish in Europe in the past years.
Given that fish migrate naturally and the Great Lakes connect with the Mississippi River, which in turn runs into the Gulf of Mexico, virtually all the US government can do to prevent the virus from spreading is to limit human movement of potentially infected fish (ie, use as bait, sale to farms as breeding stock and so on).
The disease does not harm humans, even if they do eat contaminated fish.
United States Department of Agriculture