Greens co-leader Rod Donald was killed by a "very rare" complication of a common food bug, according to the Christchurch coroner.
The MP was known to have been ill for several days before his death on November 6, 2005, suffering stomach cramps, diarrhoea and vomiting. He had told people he had food poisoning.
Coroner Richard McElrea said today that Mr Donald died of a heart infection following a bout of illness due to campylobacter.
Mr McElrea said he had decided not to hold an inquest into the death, as Mr Donald's immediate family was not seeking one, and Mr Donald "contracted campylobacter jejuni from an unknown and probably unknowable source".
The need to draw attention to wider public health issues could be met by releasing part of a report by the Canterbury medical officer of health, Alistair Humphrey.
Dr Humphrey said though New Zealand had the highest incidence of campylobacter in the Western world, only about 6 per cent of all cases were hospitalised.
"The mortality from campylobacter is extremely low -- less than 0.05 per cent of all infections," said Dr Humphrey.
"Myocarditis as a complication of campylobacter infection is extremely rare".
Dr Humphrey said antibiotics such as erythomycin could eliminate the bacteria from infected people within three days, but their use was controversial and only recommended in severe cases.
It was important that such treatment was not started until campylobacter had been specifically identified, as antibiotics could prolong carriage of other infections such as salmonella.
Mr McElrea said an expert report by a consultant GP, Philip Jacobs, made it clear Mr Donald's general practitioner, Alex Bartle, acted appropriately when he assessed Mr Donald on November 2.