Irish cattle are less likely to transmit E.coli

Ireland may be uniquely placed to avoid the worst effects of global increases in E.coli 0157 food poisoning cases because Irish cattle are mostly reared on a grass-based diet, it has emerged. US research shows that cattle, the single biggest source of the potentially fatal bacteria, are much more likely to transmit it to humans when fed grain-based diets.

Countries with low grass yields, including those with large intensive cattle-rearing operations, invariably use grain as the major feedstuff.

But research by microbiologists with the US Department of Agriculture (USDA) and Cornell University indicates a simple change in cattle diets in the days before slaughter may reduce risk of human infection. Their findings, published in Science journal, suggest that feeding cattle hay instead for five days before slaughter dramatically reduces the number of acid-resistant E.coli.

The extent of reliance on grass-based feed on Irish farms (linked to a temperate climate and high rainfall) is likely to be even more successful in reducing transmission of E.coli 0157 which causes more than 20,000 infections and 200 deaths annually in the US.

Incidence in Ireland is low but increasing, while food safety experts fear the Republic may be about to follow the UK and US where cases have risen sharply.

"Most bacteria are killed by the acid of stomach juice but E.coli from grain-fed cattle are resistant to strong acids," said Dr James B. Russell, a USDA microbiologist who works with Cornell University. "When people eat foods contaminated with acid-resistant E.coli, including pathogenic strains like E.coli 0157:H7, the chance of get sick increases."

While E.coli is a normal constituent of the gastrointestinal tract in humans and cattle, its harmful types can cause severe diarrhoea and kidney failure, particularly in children, older people and those with compromised immune systems.

The Irish level of E.coli 0157:H7 in cattle has yet to be quantified, although it has caused one death in Ireland. The US estimates that less than 2 per cent of cattle shed it in their faeces, a rate yet to be fully explained. While it can easily be killed by proper cooking and irradiation, it continues to cause huge public health problems.

The findings "may explain why the incidence of E.coli 0157 is low in Ireland, as most of our cattle are fattened on grass", said the chief executive of the Food Safety Authority of Ireland, Dr Patrick Wall.