At least 62 people came down with the food bug Salmonella which was not previously thought able to survive in acidic fruit juices.

Researchers from the Centers for Disease Control and Prevention (CDC) traced the 62 cases in 21 states to a batch of unpasteurised orange juice sold at Disney World in 1995.

They found Salmonella on toads living around the juice processing plant.

Reptiles and amphibians are known to carry the bug.

Writing in the Journal of the American Medical Association, the researchers say that the processing plant had cracked walls.

Mice and bird droppings were found inside and frogs had got into the building.

Long investigation

The investigation took many months as the researchers first had to identify a link between the 62 cases.

They found that they had all visited Disney World in the summer of 1995 and had all drunk orange juice.

Many had stayed at the same hotel. The researchers then had to trace the orange juice and test it for Salmonella.

They inspected all the processing facilities and farms where the juice was made before finding the one processing plant which was the cause of the outbreak.

The researchers think the orange juice was responsible for many more Salmonella cases than the 62 which were reported.

They say most people do not report sickness.

Salmonella causes diarrhoea and vomiting, but can be treated with antibiotics. However, it can prove fatal in elderly and vulnerable people.

Pasteurisation debate

Fruit juices are generally thought not to cause sickness because of their acid content.

The researchers, led by Kim Cook, wrote: "Orange juice and other acidic fruit juices are generally believed to be unusual vehicles of transmission for human pathogens."

Toads are carriers of Salmonella

They stated, however, that there had been an E. Coli traced to unpasteurised apple juice in 1996 and said the Salmonella outbreak showed the need for the pasteurisation of fruit juices.

The US Food and Drug Administration (FDA) has recently tightened regulations on the labelling of fruit juice, making it illegal for people to sell unpasteurised fruit juices without warning consumers of the dangers of harmful bacteria being present.

The National Food Processors' Association wants all juices to be pasteurised so that any bacteria are killed off in the heating process.

It welcomed the CDC's conclusions and called on the FDA to make pasteurisation mandatory.

In a statement, it said: "While 98% of the juice sold in America is already pasteurized, FDA estimates that 5 million gallons of juice a year would include a warning label -- more than 85 million servings.

"Clearly, this is not a problem limited to small 'lemonade stands.' Frankly, there is no precedent for FDA allowing a product it cannot assure is pathogen-free to be sold when an effective technology exists to eliminate this problem."