Diseases Associated with Salmon Farms By Jayme Longo

Food hygiene  Responsibility for fish and shellfish hygiene issues falls under the remit of the Food Standards Agency (FSA).

Is Disease in the Wild Normal?  co-evolution  healthy salmon may harbor organisms  many pathogens are opportunistic In the wild, stress can come from: increased population densities. changes in food availability. sudden changes in environmental conditions.

What’s Bad About Fish Farm Disease?  Wild salmon are not subjected to high population densities nor do they undergo human handling. Thus: artificial envt. = more stress than the wild  Stressed fish produce hormones that suppress the immune system.  This increases the risk of disease and allows for rapid transmission. Thus: salmon farms = disease amplifiers

Key Diseases that Affect Salmon Farms  Sea Lice  Bacterial Kidney Disease  Furunculosis  Vibriosis  Kudoa

Sea Lice Sea Lice = small crustaceans that act as parasites for salmon and related species. Juvenile pink salmon infested with sea lice (© Alexandra Morton)

Sea Lice Sea Lice = small crustaceans that act as parasites for salmon and related species. Farms increase Sea Lice populations:  Lice population rises to 20% > normal.  Atlantic Salmon are most susceptible to sea lice.  There is a reduced flow of seawater through the farm. Danger to Trout Migration: Ireland's Western Regional Fisheries Board pointed to an increase in sea lice from fish farms as the sole cause of sea trout collapse.

Bacterial Kidney Disease The disease is highly infectious with vertical transmission.

Bacterial Kidney Disease 80% of all disease losses on Pacific salmon farms 40% of all losses on Atlantic salmon farms (BKD alone). Bacterial diseases are treated by antibiotics and/or immunization. Bacteria’s Superior Survival Tactics:  It can survive outside of the host for horizontal transmission.  It can survive in sediment and sewage for up to 21 days.  Fish afflicted with BKD are usually: lethargic, dark-colored, partially blind w/ abscesses under skin, which can break open into the water. (abscesses & feces=BKD) The disease is highly infectious with vertical transmission.

Furunculosis

Furunculosis  This bacterium can be very long-lived. It can be transmitted between unrelated salmon farms (24 km). It is found in high concentrations in sediments (salmon farms).  Main method of control is vaccination, but outbreaks continue, at which point antibiotics must be used. Often, the bacterium becomes resistant to antibiotics used against it.

Vibriosis  Vibriosis is caused by several diff. strains of bacteria. (marine fishes & invertebrates).  Key transmission method is from the feces of infected fish. sewage  wild fish  Vibriosis bacterium can survive in seawater for >1 year.

Kudoa  Kudoa is caused by a microscopic parasite which can attack farmed Atlantic salmon and marine fishes.  It rarely causes mortality. It’s mainly of economic concern due to white cysts and softening of flesh.  Little is known about how the disease develops or transmits. (no treatment)

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