Farmed fish are avoiding BSE contamination so far

European experiment suggests little risk of mad cow disease or scrapie

By Thanassis Tsinganas - Kathimerini

The fear that bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, might infect other species prompted the European Commission to set up a European BSE Research group in 1996.

Although the nightmare of BSE itself has receded, the possibility of cross-species transmission is an ongoing concern. Fish farms, where the fish are fed with products that may contain animal protein, could be at risk. An experiment that is being conducted in five European countries and coordinated by Greek scientists is investigating whether spongiform encephalopathies can be transmitted to fish through contaminated food. So far the evidence suggests that fish are not vulnerable, but a definite answer must wait until 2007, when the program concludes.

In Greece, researchers are focusing on sea bass and sea bream, the species most commonly found in fish farms; in Spain they are looking at trout, in Norway at salmon and in Germany at aquarium fish, which are of commercial importance, while Italian laboratories are observing BSE in the digestive systems of fish.

All the research is being coordinated by Thessaloniki University's pharmacology laboratory and spongiform encephalopathies team under the direction of Professor Thodoros Sklaviadis.

The researchers fed the fish with matter taken from the brains of sheep infected with scrapie, a transmissible spongiform encephalopathy (TSE), and of cows infected with BSE. The fish are given the contaminated food when very young and the researchers observe them throughout their lives to see if they develop any symptoms, comparing them with a control group. At regular intervals they remove a small number of fish for anatomical and biochemical checks.

Prolonged observation is needed because TSEs take a long time to develop, and this is the first experiment of its kind.

The Thessaloniki team had to start from scratch, studying the fish brains to discover the role played by the prion proteins associated with TSE development. They found that the prion proteins of mammals differ considerably from that of fish, which is thought to be one reason why the fish have not contracted the disease so far. «When the project is complete we will be in a position to say whether or not BSE can appear in fish,» said Sklaviadis.