Officials fine-tune salmon virus response

As Maine salmon farms begin recovery, officials remain vigilant
By Bridget M. Kuehn
Published on
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Under close state and federal scrutiny, some salmon farmers in Maine began restocking their pens May 1 in an effort to recover from an outbreak of infectious salmon anemia that decimated the 2001 crop.

The ISA virus, which is harmless to humans and other mammals, forced farmers to destroy about 2.6 million fish, said Dr. Steve Ellis, a veterinarian for the Department of Agriculture.

The 2001 outbreak occurred at Cobscook Bay, where most of Maine's salmon pens are located, and has cost the more than $100 million Maine salmon industry about $24 million, according to preliminary estimates from the USDA Animal and Plant Health Inspection Service.

Federal officials approved emergency status for ISA in December—the first time the USDA has given emergency status to an aquatic animal disease. On April 5, 2002, an interim amendment to federal regulations went into effect allowing the government to make indemnity payments to salmon farmers who had to destroy fish because of ISA.

According to the USDA-APHIS, clinical signs of ISA, also called hemorrhagic kidney syndrome, include lethargy, swelling and hemorrhaging in the kidneys and other organs, protruding eyes, pale gills, and darkening of the caudal portion of the gut.

In response to the outbreak, the Maine Aquaculture Association adopted an Infectious Salmon Anemia Action Plan that was later approved by the Maine Department of Natural Resources.

Meanwhile, officials from the DNR and the USDA have taken steps to contain and control the virus:

  • In January, the USDA opened an office in East Port, Maine to provide local oversight for the Cobscook Bay farms.
  • The USDA instituted mandatory monthly veterinary checks for the entire Maine salmon industry. The veterinarians monitor mortality and biosecurity, and test fish for ISA.
  • Salmon pens where infections had occurred were required to lie fallow for 90 days before new fish were introduced. During the fallow period, farmers were required to sanitize nets, cages, and equipment.
  • The number of fish pens and the number of fish in each pen were reduced in Cobscook Bay to reduce transmission of the virus.
  • Stringent biosecurity measures were put in place to reduce the risk of cross-contamination of pens by equipment or personnel who have not been properly sanitized.
  • Farmers were required to participate in pest control programs—created by veterinarians at the University of Maine and mandated by the state—designed to reduce the risk of infection caused by the presence of carriers of the disease, such as sea lice.

Dr. Ellis and his colleagues at the DNR are carefully monitoring the population of sea lice in the area.

"Our biggest concern at this point is reducing the risk of contact with vectors of the virus, namely sea lice," Dr. Ellis said.

Dr. Paul Waterstrat, a veterinarian with the Maine DNR, said improving communication with Canadian officials and fisheries also is a priority

"There's a considerable amount of interaction with New Brunswick," Dr.Waterstrat said, adding that at a recent meeting of U.S. and Canadian officials, both sides agreed there was a need to create a more formal system for exchanging information.

Veterinarians from across the United States have had a large role in dealing with the outbreak and working to prevent future outbreaks.

Dr. Myron Kebus, a Wisconsin aquaculture veterinarian, was one of the veterinarians called upon to help. He conducted an epidemiologic survey and prepared an information sheet for farmers explaining biosecurity measures.

"Maine is an important example where veterinarians are playing a major role [in the aquaculture industry] as private practitioners working with farmers, and as veterinarians at the USDA, DNR, and university levels," Dr. Kebus said.

To promote more national and international cooperation between veterinarians and other experts on ISA, the USDA-APHIS is sponsoring a symposium, called the "International Response to Infectious Salmon Anemia: Prevention, Control, and Eradication," on Sept. 3 in New Orleans in conjunction with the 4th annual International Symposium on Aquatic Animal Health. The AVMA, the U.S. Geological Survey, and the National Marine Fisheries Service are co-sponsoring the event.

At the symposium, experts from Norway, Scotland, Denmark, Canada, and the U.S. will present the most current information on applied science and research, applied diagnostics, management practices, and the regulatory status of ISA in countries where the disease has occurred, said Dr. Otis Miller, chairman of the symposium and national aquaculture coordinator for APHIS.