Common fungal infections are “becoming incurable” with global mortality exceeding that for malaria or breast cancer because of drug-resistant strains which “terrify” doctors and threaten the food chain, a new report has warned.
Writing in a special “resistance” edition of the journal Science, researchers from Imperial College London and Exeter University have shown how crops, animals and people are all threatened by nearly omnipresent fungi.
“Fungal infections on human health are currently spiralling, and the global mortality for fungal diseases now exceeds that for malaria or breast cancer,” the report notes.
While the problem of bacteria becoming resistant to commonly used antibiotics has been widely reported on, and likened to the “apocalypse” by medical leaders, the risks of disease-causing fungi have received far less recognition.
Fungicides share a problem with antibiotics in that the organisms they aim to kill are becoming resistant to treatments faster than they can be developed, and there are growing numbers of people vulnerable to infection.
“We’ve got increasing numbers of immunosuppressed patients, that’s what fungi love to parasitise,” Matthew Fisher, professor of fungal disease epidemiology at Imperial, told The Independent.
“Half a million people a year probably die from fungal meningitis in Africa, which wouldn’t affect them if they didn’t have Aids.
“Similarly in the UK we have transplant patients as well, as soon as you whack them on immunosuppressants they start coming down with fungal infections.”
“Transplant doctors are absolutely terrified of these fungal infections,” he added, and the same issues arise in cancer patients, or people whose immune systems are destroyed by disease or age – leaving them unable to fight off infection on their own.
Our immune systems have evolved alongside fungi for millennia to keep us protected against the ever-present pathogens.
Unlike bacteria on surfaces and water droplets, fungi are much better at getting airborne and there are at least five types of potentially disease-causing spores in every breath.
“Compost heaps are absolutely lethal if you don’t have fully functioning innate immunity,” said Mr Fisher.
“If you dig into a heap and get a puff of powder, that will be aspergillus fumigatus.
“If your lung macrophages [white blood cells], don’t mop those spores up, they’re absolutely happy growing at 37 degrees and they’ll just rot you down as quick as a flash – that’s a heavy-duty pathogen.”
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“They’re looking for protein and carbohydrates – that’s all we are to them,” he added.
These airborne strains are also being joined by blood stream infections, which are particularly harmful to patients in hospitals and intensive care.
Candida auris (a species of fungus) was first identified in 2009, in an ear in Japan. Now the potentially deadly and highly drug-resistant relative of thrush infections has gone global and infected 200 people in NHS hospitals last year.
There are currently only four classes of fungicide that can be used in humans, far fewer than classes of antibiotics. This is partly due to humans and fungi being more genetically similar than humans and bacteria, meaning that many drugs which kill fungi will also potentially kill humans.
Our existing treatments are being worn out rapidly, partly because antifungal medicines are given in long courses – such as for cystic fibrosis patients whose lungs are very susceptible to resistant infections.
It’s also partly down to the widespread use of fungicides in farming.
“The azoles are our frontline class of antifungals, but they’re also the frontline fungicide in agriculture,” Mr Fisher said.
“They’re absolutely everywhere, we spray hundreds of thousands of kilos across the UK countryside and we use enormous quantities in our patients.”
The Netherlands, one of the most intensively farmed countries on the planet, is also a hotspot of resistance, and tulip bulbs – of which it exports billions every year – require intensive antifungal treatment.
“I’m not saying the Dutch bulb industry is infecting these patients, but actually it probably is contributing,” said Mr Fisher.
“This review highlights the huge increase in resistance to many of these drugs around the world, driven in part through commercial use in agriculture,” said Professor Gordon Brown, director of the Medical Research Council’s Centre for Medical Mycology.
“Given the high rates of mortality of these infections, these disturbing trends suggest that even our limited ability to treat these diseases is being severely compromised.”
The race is on to develop new drugs, and the review shows there is promise here.
There are around 11 in early clinical trials – though many will likely fail in human testing – and improvements in transplant and HIV medicines can limit fungal resistance. There are also entirely new fields of treatment such as “RNA interference”.