How often do you see fungal disease? When I went through veterinary school we learned about a few key fungal pathogens, such as cryptococcus and aspergillosis, but I was left with the impression that - at least in Australia - fungal disease is a clinical rarity. Something to get excited about and write up when you see it.
But fungi are truly everywhere. Apparently, one in four people reading this blog is suffering from, or previously had suffered from, a fungal infection – though I stress there is no causal relationship. The majority of fungal infections are relatively minor in immunocompetent humans and animals, causing disease of the skin, hair and nails (or claws, depending on the species). Tinea or athlete’s foot and thrush are the most well-known examples. These are localised, typically minor diseases (although they can be florid in some cases). But fungal disease can be deadly.
According to the GlobalAction Fund for Fungal Infections, several groups of humans are particularly vulnerable to invasive fungal disease (also known as IFD to those in the business):
- Patients with cancer, leukaemia, AIDS and transplant patients
- Critical care patients – premature babies, intensive care unit patients, people having major surgery
- Patients with lung disease – severe asthma, tuberculosis, chronic obstructive pulmonary disease and cystic fibrosis
- Patients with injuries – eye injuries, burns, trauma, wounds
- Sexual health patients – usually women with recurrent thrush or candidiasis, especially in pregnancy
As I have mentioned previously I have hosted a visiting mycologist at my house. Every scientist thinks their field is important, and this mycologist was not an exception. Her enthusiasm was palpable, infectious even – and her colleagues were similarly passionate. But it wasn’t until I attended the International Society for Humanand Animal Mycology, I had an epiphany of sorts: we all really, really, really need to be very aware of fungal disease.
|Some members of the ISHAM veterinary mycology working group: Dr Madhi Alshahni, Dr Sandra Bosco, Dr Seyedmojtaba Seyedmousavi, Dr Patrizia Danesi, Professor Sybren de Hoog and Dr Andrea Peano.|
Why? Because it affects so many people and the incidence of fungal disease is increasing – probably due to climate change. Even if you aren’t particularly concerned about veterinary mycoses, it’s worth appreciating the human health burden.
Over a billion people globally are affected by fungal disease, 11.5 million suffer life-threatening infections and fungal diseases claim over 1.5 million human lives per year (GAFFI). Fungi account for around 10 per cent of hospital acquired infections with mortality rates ranging from 50-100 per cent.
Approximately 30 species of fungi are responsible for 99 per cent of human cases. But, particularly in developing countries, diagnosis might be slow, treatment is costly if accessible at all, and the drugs have a narrow therapeutic window and may cause toxicity.
When it comes to one of the most common veterinary fungal diseases, ringworm or dermatophytosis, diagnosis can be costly and very slow. You need at least ten days for a fungal culture, although I learned at the conference that at least one group is working on a PCR test that will enable diagnosis and identification of the specific pathogen involved.
Here are a few useful things I learned about fungi:
- Look for fungi. Cutaneous lesions, mass lesions, systemic diseases can all be caused by fungi, but it’s hard to work that out if you don’t consider it in the first place. When taking a histopath sample, keep some in the fridge for potential fungal culture. Perform cytology on aspirates or impression smears. Consider potential fungal exposure/inoculation – is there a penetrating wound? Is the distribution of lesions suggestive of exposure to a saprophyte? Is the animal in contact with a known environmental niche of a fungal organism? (What is the travel history?)
- Fungi are often secondary pathogens – though not always. But fungal infection in animals and humans can indicate poor underlying health (e.g. immunosuppression), environmental changes (climate or microclimate, habitat destruction) or inoculation of contaminants.
- Veterinarians and pet owners can contribute to knowledge of fungal disease. This is a new field and in a meeting of ISHAM’s Veterinary Mycology Working Group it became apparent that any case of fungal disease in animals is worth documenting. Recording as much history as possible, photographing lesions, ensuring the diagnosis is confirmed (this might involve PCR or tests that are not readily available to veterinarians – don’t give up! Ask a medical mycologist), documenting treatment and response etc. is all valuable.
If you’re fired up about mycology, consider a trip to lovely Italy in October this year where you can undertake a course on veterinary mycology at the University of Turin.
You can also visit the mycology working group at www.veterinarymycology.org
GAFFI (2015) Improving outcomes for patients with fungal infections across the world: a roadmap for the next decade. 95/95 by 2025.
Meyer W & Irinyi L (2015) Facing the challenge of growing numbers of fungal infections – sequence based fungal identification using the ISHAM-ITS reference database. The Broad Street Pump 38:P9-10.