"It is unclear why we have this resurgence of outbreaks now but increased ocean temperatures may be one of the reasons," said Tor Atle Mo, at the National Veterinary Institute.
"The sea gradually becomes warmer in the great waters during autumn. Higher average temperatures can provide favorable growth of amoeba. At the onset of 2006, the average sea temperature was four degrees higher than usual."
Mo says that the infection does not affect all farms equally as hard. Some people have not had big problems with the infection, while others suffer from high mortality.
"This may be related to the health status of the fish before it hit. In some installations where salmon are exposed to other stressful influences, amoebae may be the final blow that breaks the salmon. We also believe that some salmon stocks can be a bit more resistant to amoeba than others, but this remains to be investigated," he said.
"Often it is a complex issue behind AGD and it is hard to say if it is amoeba alone that cause mortality. We know from infection experiments we have done at VESO Vikan that the amoeba itself is potentially fatal.
