An illustration of trichophyton rubrum fungi - showing macroconidium, microconidia and septate hyphae. Photo: AFP / KATERYNA KON / SCIENCE PHOTO LIBRA
A new strain of drug-resistant fungus that causes ringworm has been found in New Zealand and scientists are warning doctors to look out for "suspicious infections".
Dermatophytosis, or ringworm, is one of the most common fungal infections worldwide, caused by fungi called dermatophytes infecting skin, hair and nails.
A strain of dermatophyte - trichophyton indotineae- that is often resistant to treatment has been spreading globally and has now reached Aotearoa, a study published in the New Zealand Medical Journal has found.
"We alert those seeing patients with suspicious infections to get cultures and order full identification so patients can be managed appropriately," it said.
Researchers analysed 961 dermatophyte samples taken between January 2017 and August 2024 from a range of hospital and community laboratories.
They found 85 confirmed or probable cases of the strain from 63 patients, most of whom were infected in the groin, thighs, feet and arms.
Clinical Microbiologist at Auckland Hospital Dr Arthur Morris told Checkpoint primary care workers needed to be aware of the new strain.
"At a population level it's not a grave concern, but it would be of concern for households and family units, because ringworm and these, kind of, dermatified funghi are spread reasonably easily within a household."
The new variant was more resistant to treatment and caused "quite extensive infection", he said.
"The usual go-to, Terbinafine or Lamisil won't work."
While ringworm was typically limited to single locations on the body, the new variant could spread over "large areas of the abdomen, thighs, buttocks ... multiple areas on the same person", Morris said.
The development of the drug resistant strain was put down to the use of "basic skin cure-all" medications, he said.
"It's put down to the widespread use of 'across the counter' medicines that contain high-dose steroids, anti-fungal and an antibacterial.
"If you put that on enough people you're going to select out those strains that are resistant," he said.
The main purpose of publishing the study was to raise awareness of the new strain so that people could look out for it, he said.
"Microbiologists are sort of familiar with it, and dermatologists, maybe. But it wouldn't be all that well known in primary care, and that's was the reason we put it into the med journal."
"If it's not responding to Lamisil or Terbinafine, then an 'azole' like Itraconazole is the drug to go for. And people may have to be treated for a few months under careful review," he said.
Terbinafine is the most common treatment for ringworm, but it did not work on more than a third of the 85 cases, the study found.
Instead itraconazole was the best treatment, clearing up 92 percent of cases.
The researchers were planning a more in-depth analysis, but in the meantime they warned GPs to look out for cases of "long-standing" infections especially in people from India and South Asia, where there have been large outbreaks.
Those cases should be treated with itraconazole for up to 12 weeks, it said.
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