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Kiwi experts zero in on new possible cause of rheumatic fever

Dr Lance O'Sullivan. Photo/Simon Young

Experts are starting to rethink the causes of rheumatic fever.

It’s long been known that Group A streptococcus in sore throats can trigger the self-sabotaging immune disease. But now many New Zealand and Australian researchers and medical professionals, interviewed by the Listener for this week’s cover story, believe strep A in skin infections is likely playing a causal role, too.

“At this stage I would say the evidence is firming up that some forms of skin infection are also likely to be an important cause,” says Michael Baker, a professor of public health at the University of Otago.

The latest strand of science is a case report by Kaitaia GP Lance O’Sullivan and co-authors, involving a Northland boy diagnosed with rheumatic fever in 2015. The boy’s sore throat tested negative for strep A – but he had a strep A-infected skin infection, impetigo, in the run-up to diagnosis.

The case is detailed in July’s Pediatric Infectious Disease Journal.

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It comes on top of microbiological evidence from the Maurice Wilkins Centre for Molecular Biodiscovery at the University of Auckland. Two studies of strep A-positive throat and skin swabs from New Zealand have found a surprising prevalence of strains usually found on the skin.

Epidemiological evidence from Australia and Fiji – where indigenous peoples are stricken by rheumatic fever and skin infections, but rarely get sore throats – also points to the skin as an important cause.

For some, the mounting evidence partially explains the outcome of the six-year, $65 million rheumatic fever prevention programme that focused on swabbing and treating sore throats in schools, as well as urging parents to get kids’ sore throats checked. “Rheumatic fever – it starts with a sore throat,” the campaign claimed.

The programme finished in June, having failed to meet the Government’s target of pushing the rate of rheumatic fever down to 1.4 cases per 100,000 people. The rate is now about 3 – that’s 137 new diagnoses last year. All but 12 were Maori or Pasifika.

Health Minister Jonathan Coleman, a former GP, says the programme was effective and rheumatic fever “has always been a tough one to catch”.

“But maybe this skin [research] might be a way of really getting that number down a bit more. It’s interesting.”

For more on rheumatic fever and its devastating effects in New Zealand, pick up a copy of the July 29, 2017 issue of the New Zealand Listener.