The unexpected health challenge to the stock in 2012 was caused by a bloom of a naturally occurring single celled marine amoeba organism. This organism which is not a pathogen as such caused severe irritation to the gills of the farmed fish concerned. There were severe stock losses of the smaller sized fish as a result. This phenomenon had been observed previously in 1999 in Ireland but had not been seen in the interim.
This phenomenon has also been evident in other jurisdictions and, in Australia, a treatment technique was developed which involved immersing the affected stock in freshwater for a short period. The fresh water kills and removes the amoeba by osmoregulatory stress on the organism but the salmon remain unaffected and are effectively ‘cured’ by the treatment.
This treatment is now being used by Irish operators to deal successfully with the problem. It should be noted that this condition, known as Amoebic Gill Disease or AGD has no implications whatsoever for human health or for the health status of any wild stocks of fish.