Stomach bug rise linked to effluent

By SIMON COLLINS, science reporter

Cows producing the equivalent of untreated effluent from 52 million people are being partly blamed for an escalating epidemic of campylobacter food poisoning.

Reported cases of the campylobacter stomach bug have multiplied more than 16-fold in the past 20 years, from 769 cases in 1982 to a record 12,489 cases last year.

New Zealand's rate is now several times higher than in any other developed country.

A public health doctor with the Ministry of Health in Dunedin, Dr Marion Poore, told the New Zealand Geographic Society conference in Auckland yesterday that one of the reasons for the increase was effluent from cows seeping into waterways.

"Between 1990 and 2002, the national dairy herd increased 51 per cent to 5.2 million cows.

"They produce the equivalent effluent to 52 million people," she said.

"Only a very small proportion of that effluent is treated. Most lies around on pastures and ends up in agricultural runoff."

Dr Poore said New Zealand was grappling with increasing rates of a wide range of waterborne bugs, including giardia, cryptosporidium and salmonella.

A study last year found that 23 per cent of the country's cases of salmonella infection came from contaminated water, a further 23 per cent each from direct contact with farmed animals and contaminated food, 16 per cent from overseas travel, 11 per cent from personal contact with infected people and 9 per cent from contact with faeces or vomit from an infected person.

Dr Michael Baker, a public health physician with the Institute of Environmental Science and Research (ESR), said later that New Zealand's total untreated effluent from cows, sheep and other animals might be equivalent to a human population of more than 200 million.

"In a country comparable in size to Britain or Japan, we have a massive burden of untreated sewage."

He said the link between this and campylobacter was still speculative, and studies had found no significant difference in rates of the disease between rural and urban areas.

The biggest immediate source of campylobacter in New Zealand was chicken - tests showed the bug was present in more than half of all poultry.

"Many people have linked the rise to the increase in poultry consumption," he said.

But other studies suggested that New Zealand's high rate compared with other countries was due to "an entire environment which is very heavily contaminated with campylobacter".

A study for the Environment Ministry last year found campylobacter in 60 per cent of water samples taken at 25 sites throughout the country.

Dr Poore said farmers could limit the amount of effluent getting into waterways by fencing off streams, planting trees and shrubs on stream banks and limiting stock numbers in at-risk areas.

"We are all responsible. We all have a part to play in this.

"Our collective wisdom and knowledge need to be made available to our communities in order to make sure that we have a safe world in which to live."