Flies and cattle blamed for food poisoning rate

Flies and the proximity of most New Zealand cities to cattle are to blame for the country's astoundingly high rate of campylobacter food poisonings, a new study has found.

The research, which appears in the New Zealand Medical Journal today, says eating chicken is also a "significant risk factor".

The study warns that takeaway chicken meals are particularly risky if food is eaten without washing hands.

However the paper concludes that the sporadic nature of campylobacter illnesses and the seasonal pattern of infection, which peaks in warmer months, indicate that chicken meat itself is not the major source of infection.

Last month an Otago University study suggested that 90 per cent of fresh chicken sold was contaminated with campylobacter.

New Zealand has a high rate of campylobacteriosis with up to 14,000 reported cases annually.

Laboratory scientist Ben Harris, who co-wrote the paper with research consultant Warrick Nelson, estimates that the occurrence of the illness is between 10 and 20 times higher than reported because most people don't report food poisoning.

They analysed campylobacter incidents, regional temperatures and chicken consumption data.

Mr Harris said: "As soon as the temperature increases, the human campylobacter rates increase ... too."

Campylobacter outbreaks tend to be sporadic but with other causes such as salmonella, the tendency is for "cluster outbreaks" of 20 to 30 people.

Mr Harris said flies were the link between environmental sources of campylobacter and food. In New Zealand, the primary source of infection is thought to be the faeces of dairy and beef cattle.

It was the proximity to rural environments that allowed flies to transmit the bacteria to food, particularly during the warmer months when they are most active.

The bacteria is transferred through fly faecal deposits on common surfaces such as hand rails and door handles. Campylobacter deposited on fingertips can survive for at least an hour, and have been recovered from dry surfaces 24 hours after being deposited.

Mr Harris said poisonings are also caused by poor food preparation practices or improperly cooked chicken.

"Many people actually don't cook it all the way through, or if it's a stuffed chicken, it's harder to cook it all the way through.

"So you often think, if you can have a rare steak, why can't you have a rare chicken?

"The reason is the steak does not have an intestine. There is no campylobacter in the middle of the steak ... There is in the middle of the chicken.

"The poultry industry will say if you cook it properly you won't have any campylobacter. That's quite true, but in practice ... preparation methods are not good enough to handle something that's got large numbers of campylobacter on it."