Many millions more people than previously thought could be infected with the foodborne parasitic disease toxoplasmosis.
It is estimated that up to 10M people in the UK carry the parasite toxoplasma and the most likely cause of infection is contaminated meat and vegetables, an expert on the disease told the Food Standards Agency's Advisory Committee on the Microbiological Safety of Food (ACMSF).
While the environment and, in particular, cat faeces had been blamed as the main sources, Dr Edward Guy from the Toxoplasma Reference Unit (TRU) at National Public Health Service for Wales said latest unpublished data from Europe suggested that 60% of cases arose from food.
"It is clearly a significant factor in mainland Europe," said Guy. "Cats actually get quite a bad press." However, more studies were necessary to identify the extent of the problem.
Historically, there had been under-reporting and a lack of comprehensive surveillance. Part of the problem may lie with toxoplasmosis not being a notifiable disease in England and Wales, he suggested. While there were 117 cases reported by NHS labs in 2006, TRU had identified 667.
Some ACMSF members urged caution about overstating the risk. ACMSF committee member and Sainsbury's chief microbiologist Alec Kyriakides said: "We need to be clear about the risk this presents - it could be quite an explosive topic."
Toxoplasma does not cause a health problem for most people. Some 85% of those infected do not report any illness, said Guy. But for pregnant women, their babies and those with immunosuppression - such as HIV - the results can be far more serious and even fatal.
Refrigeration at temperatures below -20°C and heating food above 65-67°C kills the parasite, said Guy. "Meat that is frozen probably presents no risk at all."
A French expert on toxoplasmosis also claimed that contamination with toxoplasma in the UK meat chain - particularly from outdoor reared pork - is much higher than generally believed. Dr Pascal Boireau, a director at AFSSA - the French equivalent of the UK's FSA - claimed that 80% of toxoplasmosis contamination was from meat and the threat from livestock was real and growing. In France, where infection rates are running at 10% to 20%, cross contamination to outdoor pigs from wild boar was a particular problem, he said.