INFECTIOUS SALMON ANAEMIA IN THE UNITED STATES OF AMERICA
Information received by OIE on 16 June 2003 from Dr Peter Fernandez, Associate Administrator, Animal and Plant Health Inspection Service, United States Department of Agriculture (USDA), Washington, DC:
Report date: 16 June 2003.
Nature of diagnosis: laboratory.
Date of initial detection of animal health incident: 11 June 2003.
Estimated date of first infection: 9 June 2003.
Outbreaks: Location: Broad Cove, Cobscook Bay, State of Maine. No. of outbreaks: 1 farm
Description of affected population: Atlantic salmon( Salmo salar ).
Total number of animals in the outbreak: species: pis.; susceptible: 28,000; cases: 1 cage; deaths:
destroyed: 0; slaughtered: 28,000
This is the first incidence of infectious salmon anemia (ISA) virus in Maine since the ISA outbreak in the spring of 2001 (see Disease Information , 14 , 65, et seq. ). The surveillance programme that was implemented as a result of the 2001 outbreak allowed early detection of the virus.
Following the outbreak of 2001, all infected and exposed sites were depopulated, cleaned and disinfected. Sites were fallowed for up to 90 days. Some sites were restocked in the spring of 2002. Biosecurity measures were implemented, an integrated pest management programme implemented (for sea lice), control of transportation movement implemented, and single year-class farming implemented. All farms participate in the USDA ISA programme. As part of the surveillance programme, low-risk sites are sampled monthly, and high-risk sites are sampled twice a month. It was through this surveillance programme that the samples which led to this detection were taken on 9 June 2003.
A. Laboratory where diagnosis was made: MicroTechnologies Inc., Richmond, Maine.
B. Diagnostic tests used: indirect fluorescent antibody test (positive at +3) and RT-PCR(1) (positive). Tissue samples are being cultured for definitive confirmation.
A. Source of agent / origin of infection: unknown.
B. Mode of spread: ISA virus is considered a slow spreading low virulent virus. The mode of spread of ISA virus may be passively in seawater, via sea lice as a vector, or there may be a natural host acting as a reservoir, although none of these has been confirmed in the field.
Control measures: on 16 June 2003 the farm was depopulated.
(1) RT-PCR: reverse transcription - polymerase chain reaction