Proliferative kidney disease can be especially fatal to recently introduced fish in a farm. (Photo: Aqua.stir.ac.uk/marlab.ac.uk)

Scientists discover key carrier link behind fish disease

UNITED KINGDOM
Monday, May 04, 2009, 17:40 (GMT + 9)

Biotechnology and Biological Sciences Research Council (BBSRC) researchers have discovered that fish can carry and spread proliferative kidney disease (PKD), which can infect and kill large amounts of fish, particularly in fish farms. The finding opens the door for research on more specific treatments for the disease.

The research, published in BBSRC Business, was led by Professor Sandra Adams and David Morris at the University of Stirling’s Institute of Aquaculture.

PKD provokes a severe inflammation of the fish kidneys, and is known to especially affect fish recently introduced to infected farms. The estimated annual cost of the disease's impact on the UK trout industry alone is GBP 2.5 million (EUR 2.8 million).

Although the condition’s impact on the industry has been serious and widespread, research on the PKD has been sparse until now. Scientists had previously discovered the parasite in freshwater bryozoa, which are colony-forming animals that feed on algae. Some bryozoa species can fragment to form new colonies with the potential to spread the disease to fish.

Adams and Morris have now found that native fish can also spread PKD, not just suffer from it.

"We were able to show that the parasite that causes deadly PKD in fish could cycle between brown trout and bryozoa indefinitely," Adams said, the Science Daily reports.

The team has also constructed a working model for studying the parasite’s lifecycle, information that will be imperative in developing measures to fight off PKD.

Research suggests that brown trout can host PKD despite not being particularly vulnerable to it, while UK rainbow trout can die from the disease.

"In their native environment in the US, rainbow trout are more resilient to PKD,” Adams explained. “This suggests that there are at least two strains of this particular parasite: one adapted to North American species and one adapted to European species. Therefore, rainbow trout introduced to European waters are likely to be infected with the wrong strain of the parasite, which explains the severe immune response and subsequent disease."

It appears that PKD has affected wild salmon in Europe and North America, suggesting it is a budding threat to these central fisheries.

"Farmed fish are a crucial part of the food chain, providing nutritious and affordable food for many people. They are also economically important in many areas,” remarked Janet Allen, Director of Research at BBSRC. “When a disease such as this threatens fish farming it is vital that we provide the science to understand the problem and its source and deliver the research to tackle it."

By Natalia Real
editorial@fis.com
www.fis.com

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