The planned release of vast numbers of imported dung beetles could spread nasty gut diseases, Auckland's top public health doctor has warned.
Dr Denise Barnfather made her views known in confidential advice sent last year to Landcare, a Government agency involved in a $750,000 project to release 11 exotic species of dung beetles.
Approval to import and release the insects was granted without conditions in a little-noticed decision by the Environmental Risk Management Authority in February 2011.
The group behind the project plans releases later this year, with the beetles sent to farms to eat cow dung.
Senior scientists have questioned whether enough is known about the possible risks to human and animal health. Diseases the insects could carry include E coli, salmonella, campylobacter and giardia.
Dr Barnfather, medical officer of health with the Regional Public Health Service, said the evidence was "sufficient to raise concern exotic dung beetles may provide additional vectors for human exposure to significant gastro-intestinal diseases."
Potential exposure from beetles contaminating water supplies in homes which collected rain in tanks, or among children eating dead beetles or by handling insects carrying pathogens had not been adequately researched, Dr Barnfather cautioned.
She said the insects could travel long distances, carry infective doses of disease, be attracted at night to light and be close to country towns.
Her advice concluded: "Until the significance of these potential human exposures to pathogens harboured by dung beetles are adequately researched and understood, public health recommends that a precautionary approach is taken and that exotic dung beetles are not introduced into New Zealand."
The Ministry of Health and Landcare referred inquiries to the Environmental Protection Authority, the successor to ERMA.
Its principal scientist Dr Geoff Ridley said: "The Ministry of Health was notified of the application and call for submissions, but did not make a submission.
"Rigorous science supports the expert panel's decision to allow the release of the exotic beetles.
"It is not unusual for different experts to come to different conclusions about decisions on the release of new plants and animals, however the application went through a robust process, and the EPA stands by the decision."
Auckland University's dean of science, Professor Grant Guilford, a former vet, believes not enough research has been done to justify releasing the beetles.
He says New Zealand's interests are best served by waiting until all doubts have been resolved.