State and federal officials confirmed an outbreak of infectious salmon anemia at a Maine salmon farm in June, despite renewed efforts to control the disease after a series of outbreaks in 2001 that ended in January 2002 with the depopulation of more than 2.6 million farmed fish.
The ISA virus was detected June 11 in one cage housing 28,000 market-size fish at a farm operated by Heritage Salmon in Cobscook Bay, according to the Maine Department of Marine Resources. All 28,000 fish have been depopulated and no other salmon at this farm or any other in the bay have tested positive for the disease.
ISA, a foreign animal disease, is not a human health threat, according to the U.S. Department of Agriculture. 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.
"We are obviously disappointed that (the ISA virus) has been detected in Maine, given the amount of work by farmers and the state and federal government to try and control this disease," said George D. Lapointe, commissioner of the Department of Marine Resources. "But it should be noted that the control program is just that—control."
"We should expect that we will see additional, but hopefully limited, outbreaks, until some form of definitive control for this disease is developed," Lapointe said.
An industry in recovery
The current outbreak is a blow to an industry still recovering from an ISA outbreak that spanned nine months in 2001 and ended with the depopulation of 2.6 million farmed fish in Cobscook Bay in January 2002. These outbreaks cost the Maine salmon industry at least $24 million, according to estimates by the USDA Animal and Plant Health Inspection Service, the agency leading ISA surveillance and control efforts in Maine.
For more information about previous ISA outbreaks in Maine, visit https://www.avma.org/News/JAVMANews/Pages/020701e.aspx.
After the farms were depopulated in January 2002, the pens were left empty for three months and restocked in May 2002. Tough new biosecurity measures were instituted on the farms under APHIS supervision. Measures included routine testing for the disease and audits of farm biosecurity, restrictions on boat movement at fish farms, and efforts to reduce the population of sea lice—a potential vector of the ISA virus, according to APHIS officials.
Neighboring salmon farms in New Brunswick, Canada, have instituted similar control measures but have been less successful in controlling the disease, with several outbreaks of ISA over the past 18 months, according the Maine Department of Marine Resources.
Commissioner Lapointe said agencies on both sides of the border have been working to coordinate their ISA efforts.
"All the governments involved know that we have to have coordinated programs that act aggressively and thoroughly to control outbreaks," he said. "I am more comfortable now that we have comparable programs on both sides of the border."