A new theory could explain why the Norwegian Salmon is suffering from more infections in fish farms.
Mark Lyte, a professor of veterinary microbiology and preventive medicine at Iowa State University, suggests that the farmed salmon is suffering from stress.
Historically, the fish were given large doses of antibiotics and other medicines to combat diseases. However, more physical methods are now used, including chemical treatments and delousing by physically brushing the sea lice off the salmon. Lyte theorizes that the handling is causing the fish stress, which is increasing their stress hormones and giving them infections.
Discussing his theory of how stress can suppress an animal’s immune system, he stated:
“Two animals fight and bite each other. The skin of one animal is punctured, allowing bacteria get in. At that point, why would it be in the best interest for the stressed animal with the puncture to have its immune system suppressed and not fight off the bacteria in the wound? Obviously, evolution would not have selected for that to happen…Instead, the animal’s immune system would gear up to fight off potential invaders. So stress may be good for the immune response, initially, when an animal is faced with a challenge.”
“Dealing with the stress response is nothing new to these bugs. They’ve seen these neurochemicals before fish and other animals ever existed, and they change their physiology to survive.”
For more info, go to the Iowa State University website.