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Helicobacter pylori: The dangerous germ that can lurk undetected in your gut

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A common stomach bug that can lurk undetected for years is associated with another health risk, adding to the case for testing.

The arguments in favour of taking low-dose aspirin are looking strong, with many people using it to reduce the risk of heart attack, stroke and cancers, including colorectal and ovarian. The downside of a daily dose of the blood-thinning medication is an increased chance of a bleed, particularly as we get older.

Now, it seems, there is another problem to consider, with new research published in the Medical Journal of Australia indicating that those who are host to the common stomach bacteria helicobacter pylori more than double their risk of upper gastrointestinal tract bleeding if they take a daily low-dose aspirin.

Unfortunately, you can be infected with H pylori without knowing it. “Some people have it without symptoms or complications,” says Auckland gastroenterologist Alan Fraser.

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We pick up this bug in childhood – it is believed to infect people in the first five years of life, when the stomach is less acidic and hostile. If left untreated, the bacteria remain with their human host for life, surviving by secreting an enzyme and hiding in the gastric mucus, where they start to create inflammation.

In 2005, Australian scientists Barry Marshall and Robin Warren won a Nobel prize for their work to show that 90% of gastric ulcers are caused by H pylori infection, rather than by stress, as was previously thought. Famously, Marshall infected himself in order to prove that antibiotics were an effective treatment.

We have learnt a lot about the bacteria since then, including that they are a major cause of stomach cancer. Still, H pylori is not something that tends to be tested for routinely by doctors in New Zealand.

“Among Māori and Pacific Islanders, our rates of H pylori are as high as anywhere in the world,” says Fraser. “Recent immigrants from Asia will carry relatively high rates, too. It is correlated with socio-economic status, and when those conditions improve – as they have in countries such as China and Korea – rates can plummet within a generation.”

Fraser led a 2010 study, published in the New Zealand Medical Journal, that tested Auckland schoolchildren and found 49% of Pacific Islanders were infected, 26.7% of Māori, 24.7% of Asians and 13.7% of Europeans.

The bug is thought to pass from person to person via saliva, and those who live in overcrowded conditions and poor housing are most prone to infection.

“Children get it from their parents,” Fraser says. “We know this from DNA fingerprinting studies. The same bacteria pass through three generations of a family.”

He recommends getting tested for the bug if you have a close family member who has suffered from a gastric ulcer, if there is a family history of stomach cancer or if you have ongoing problems with indigestion.

Although there is an effective breath test, it is expensive and not widely available in this country. Here, you are more likely to be offered a blood test – which gives a 20% false positive – or a more accurate faecal antigen test. If the results are positive, you will be treated with antibiotics and proton-pump inhibitors.

“Resistance of bacteria to antibiotics is making treatment more difficult,” Fraser warns. “Our standard approach is getting less effective and we’re struggling to find an alternative.”

Screening for H pylori among high-risk communities has been proposed in New Zealand but hasn’t had enough support, and the proportion of people admitted to hospital with complications from ulcers has dropped in recent years.

“There was a big push identifying people with ulcers and getting them treated,” Fraser says. “That dealt with quite a lot of the problem. Now, we have the thornier issue of cancer risk and bleeding risk – what do we do about that?”

There is still a lot to learn about this bug. Recent studies have found associations with Parkinson’s disease and certain colorectal cancers.

Since both the bacteria and aspirin are risk factors for a bleed, and their interaction has now been demonstrated to increase the possibility, the authors of the Australian study believe there is an argument in favour of testing for, and eradicating, H pylori before a patient starts on long-term treatment with low-dose aspirin.

This article was first published in the November 10, 2018 issue of the New Zealand Listener.