Socioeconomics, travel and contact with pets driving up fungal infections

When I was 13 a pathogenic fungus (or dermatophyte) colonised the skin on my shoulder blade. Our GP diagnosed ringworm – “You probably caught it from a towel in your school gym’s changing room” – and prescribed an effective ointment. Today, University of Limerick (UL) researchers are providing valuable insights into medical mycology (the scientific study of fungi), both in Ireland and internationally.

The journal Mycoses recently published two major studies undertaken by PhD student James Powell and colleagues. One study is the first detailed analysis from Ireland of fungal detections from skin, hair and nail samples, collating all dermatological mycology tests performed at University Hospital Limerick (UHL) between 2001 and 2020. Their second study is the first ever evaluation of dermatological fungal diagnostic services in Ireland.

Corresponding co-author Prof Colum Dunne is chair and director of research at UL’s school of medicine, where he and colleagues undertake translational research, finding solutions to real-world challenges like infection control and antimicrobial resistance. Prof Dunne told The Irish Times that dermatophyte infections are common, affecting a quarter of the world’s population, with asymptomatic carriage in 30-70 per cent of adults. “But over the last 20 years,” he added, “there’s been a sharp rise in incidence due to factors like socioeconomic problems, international travel, immigration from tropical countries and contact with animals, particularly pets.”

Throughout the 20-year study period, about 13,000 nail, skin and hair samples were sent to UHL for mycology testing: 67 per cent nail, 32 per cent skin scrapings and some 1.5 per cent hair. “Dermatophytes,” explains Dunne, “can be zoophilic (from animals), anthropophilic (from humans), or geophilic (from the environment) and there was a marked shift from zoophilic species to anthropophilic species. For example, among fungal positive skin and hair specimens, zoophilic species reduced from 54 per cent in the first five years (2001–2005) to just 15 per cent in the last five years (2015–2020).”

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Such temporal changes in fungal epidemiology, suggest Dunne’s team, highlight the importance of identifying likely sources of fungal infections and outbreaks to guide appropriate treatment. This challenge is heightened because, Dunne explains, “the migration of people, especially children, during wartime is associated with increased dermatophyte infections. For instance, during conflict in the 1990s, epidemics of dermatophyte infections occurred in the former Yugoslavia, and the last year has seen a mass movement of refugees who have fled Ukraine: as of Christmas 2022, over 14 million people – mainly women and children. In that context it’s vital that these unfortunate people are protected, and that dermatophyte infections are monitored and identified to help prevent outbreaks.”

But there are problems.

During UHL’s study period, patients in primary care settings had restricted access to mycology testing services. Such diagnostic tests are time-consuming and a shortage of biomedical scientists saw testing outsourced to a referral laboratory. Accordingly, observes Dunne, “requests for mycology testing of skin, hair and nail samples were restricted to consultant dermatologists and specialist practitioners, with fewer tests performed”.

Significantly, Dunne explains, their results suggest that the main burden of disease and treatment management occurs in community settings with GPs and pharmacists having reduced access to appropriate mycology services: “With fewer samples submitted for mycology from GPs, increased dermatology clinic samples didn’t fill the gap. One possible outcome was patients being treated for fungal infections without confirmatory laboratory diagnoses or being left untreated because of little access to diagnostics.”

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This is concerning, notes Dunne, since antifungal medications can have multiple potential side-effects and drug interactions, so prolonged courses in the absence of dermatophyte confirmation are inadvisable: “Mycological identification supports diagnosis, influences antifungal therapy choice and, in select cases, provides susceptibility information for resistant infections.” This is a striking observation in the context of Dunne’s team citing evidence for antifungal resistance having been described as a “global public health threat”, with resistance to the drug terbinafine reported in Bahrain, Belgium, Brazil, Canada, Denmark, Finland, Germany, Iran, Japan, Switzerland and the United States.

Compounding the diagnostic mycology deficiencies identified by Dunne’s team are the results of a 2022 survey of Ireland’s 28 Health Service Executive’s microbiology laboratories, which found there was no hospital in Ireland with a molecular-based dermatophyte identification system available for routine use: “No respondent,” comments Dunne, “used a susceptibility testing system and, since Ireland has no national reference laboratory, isolates would be sent to the United Kingdom for susceptibility testing if required.”

Against this bleak mycological landscape is the widespread use of over-the-counter antifungals, which may promote resistance, most notably to azole drugs. “This can mean,” says Dunne, “that oropharyngeal, vaginal or even systemic yeast infections may need to be treated with less desirable alternatives such as amphotericin B with possible complications and renal toxicity.”

How can these problems be addressed? Dunne is clear: “Susceptibility testing of dermatophytes isolated from resistant infections is imperative, so access to this capability should be a priority for our diagnostic services. This would be most readily achieved by establishing a mycology reference lab for Ireland, a resource that no national health service should be without.”

These studies have garnered national and international attention due to the applied nature of the research and, says Dunne, “exemplify how university researchers working with clinicians and industry can define problems, understand them and collaborate to develop and test possible solutions in settings where they will eventually have widespread use.”