A new study has found rates of bacterial infection campylobacteriosis are twice as likely for people living in rural areas than for their urban counterparts.
Campylobacterisos can be transmitted through drinking water or contaminated food, and is a gastrointestinal tract infection that results in vomiting, diarrhoea, stomach pain, fever or nausea, and can be fatal for vulnerable people like elderly or children.
It is the most commonly reported gastrointestinal disease in New Zealand with 5000 to 6000 cases diagnosed each year, according to the National Notifiable Disease Surveillance database.
It resulted in 652 hospitalisations each year.
Study authors came from the University of Otago's department of public health, Ngāi Tahu's research centre at University of Canterbury and the Southern California University of Health Sciences.
They explored cases of the stomach bug between 2015 and 2019, comparing location, the local water source and links to intensive dairy farming.
Of the 16 types of water supplies they studied, they found the highest rates of campylobacteriosis were in rural areas that relied on private water supplies and in areas with high density dairy cow populations.
Cases were twice as likely in rural areas than in urban areas, and four times more likely for children under age five living rurally, than in urban centres.
"We also look at the risk of Campylobacter infection for children because they are more vulnerable to the effects of contaminated water," said lead author Dr Farnaz Pourzand of the University of Otago.
Rural areas on private water supplies were 1046 cases per 100,000 people - just over one percent - while areas with intensive dairy reported 978 cases per 100,000 people - just below one percent
Pourzand said their findings were concerning, but "not entirely surprising."
"We know that currently private water supplies are not monitoring and well managed as public supplies are, that means many rural households are left without the same level of protection and that is a real concern when it comes to waterborne illnesses like Campylobacter, as research shows."
The data excluded a peak of around 5500 cases in Havelock North in 2016, an outbreak linked to contaminated community drinking water that was linked to three deaths.
There were 125 cases of campylobacteriosis per 100,000 people in New Zealand in 2019, according to ESR data, which was higher than in other high-income countries like the Unites States which was seven times lower, at 19.5 per 100,000 people in 2018.
It was the leading cause of hospitalisations among notifiable diseases since 2022, excluding Covid-19.
Risks in rural areas
About 1.13 percent of the New Zealand population - around 53,500 people - lived in highest risk areas that were rural, had high dairy cattle populations or depended on private water supplies.
About 15 percent of New Zealanders relied on private drinking water supplies, like wells, boreholes, and rainwater, that were more common in rural areas.
Private supplies were unregulated and maintained locally, whereas public water supplies were treated and tested regularly to ensure they met safe drinking water standards set by regulator Taumata Arowai.
Rural risks of camperpylobacteriosis were also elevated due to environmental factors like contact with farm animals or farm run-off, which could carry faecal matter containing campylobacter to water ways.
In areas with high dairy farming, people relying on private water supplies had a 47 percent higher risk of contracting Campylobacter than those in areas without dairy farming.
Outbreaks tended to occur due to factors like heavy rainfall, sewage or issues with septic tanks.
Researchers found regions like Waikato, Taranaki, Canterbury, and Southland were at greatest risk, compared to the lower risk in urban centres like Auckland, Wellington and Christchurch.
Meanwhile, Protozoa parasites entered the Queenstown Lakes District water supplies in 2023, causing an outbreak of cryptosporidium making 72 people sick, and was likely caused by water supplies being contaminated by human faeces.
How to improve drinking water in high risk areas
Researchers warned that without regulatory oversight and treatment, private water supplies were vulnerable to contamination, especially by harmful microbes like Campylobacter.
Pourzand said despite improved regulations for public drinking water systems, there had been no additional protections for private water users.
"We are calling on the Government to extend drinking water protection to everyone and not just those on public systems," she said.
"The Ministry for the Environment with support from Taumata Arowai should expand national drinking water standards to include all private supplies, such as rainwater tanks, wells and bore water."
Researchers said policymakers could use the identified high-risk areas to guide the delivery of specific interventions, such as better water quality monitoring and improved water treatment options.
They said regional councils too could incorporate these findings into local environmental regulations, improving the management of water quality and reducing the risk of contamination in currently high-risk areas.
Farnaz said all New Zealanders deserved access to clean, safe drinking water.
Taumata Arowai said on its website, those supplying more than one household must register as a drinking water supplier and comply with drinking water standards.
However, the Water Services Act 2021 did not apply to self-supplied households.
It said all suppliers had a duty of care to provide safe drinking water.
The regulator said it was working on revising the rules for very small to medium-sized suppliers to ensure they were proportionate to the level of risk.
It said it was raising awareness of the importance of managing risks to drinking water safety through feedback on drinking water safety Plans.
It will soon consult on "acceptable solutions" but said it may be more straightforward and cost-effective for some suppliers to meet their responsibilities.
