A study disclosed on Thursday in Berlin showed that salmonella bacteria were present in 30 percent of Germany’s large-scale egg-production farms, whereas the infection rate in Scandinavian nations was below one percent.

Some of the 2 000 known salmonella varieties can trigger life-threatening gastro-intestinal illness in children and old people.

The bacteria, which are found in raw eggs and raw poultry meat, can be killed by cooking.

The figures, derived from a 25-nation pilot study, were released by the Federal German Institute for Risk Analysis in Berlin. It said the rate of infection in some eastern European nations was 65 percent or higher.

The institute said final figures would be available in the autumn.