Fungi can now evade the process by which the body defends itself; global warming, which narrows the thermal difference between humans and their surroundings, will facilitate their contact and spread in humans
The first case of a plant fungus called Chondrostereum purpureum infecting human beings has been reported from Kolkata. A 61-year-old man suffering from a hoarse voice, cough, fatigue and difficulties swallowing was hospitalised and was detected as having been infected by the fungal species Chondrostereum purpureum. This is worrisome and may be the first instance of a new danger that the human race may face in near future.
The fungus, Chondrostereum purpureum, is known to cause Silver leaf disease in plants, especially in species of rose families. However, there were no reported instances of this fungus infecting human beings from any part of the world.
Of the hundreds of millions of fungal species, only a few cause infections in humans. This may be the start of a new phenomenon when plant fungus is adapting to invade human cells by evading the process of ‘phagocytosis’.
The process, which means ‘cell eating’, happens when a cell uses its plasma membrane to engulf a large particle, giving rise to an internal compartment called the ‘phagosome’. Organisms clean and defend themselves by this process.
The case from Kolkata was detected by Soma Dutta and Ujjwayini Ray of the Consultant Apollo Multispecialty Hospitals in the city.
They detailed their findings in a paper titled Paratracheal abscess by plant fungus Chondrostereum purpureum- first case report of human infection, published recently in the journal Medical Mycology Case Reports.
The case has raised a serious concern that many such instances may happen in future.
The CT scan of the patient demonstrated the presence of a right paratracheal abscess. Photo from the study published in Medical Mycology Case Reports
Human beings with a compromised immune system are most vulnerable to fungal infection. We witnessed this during the COVID-19 pandemic. In 2021, many people in India who had developed COVID-19 contracted a secondary fungal infection from black fungus, resulting in over 4,500 deaths.
Read Down To Earth’s coverage of the black fungus cases at the height of the COVID-19 pandemic
Rising temperature due to global warming is thought of as one of the major reasons for this new threat to human beings. Most fungi thrive in the range of 12°C to 30°C. However, many species are thermotolerant and can withstand high temperatures.
In order to invade human cells, fungi, on one hand, have to be able to evade the phagocytosis pathway and, on the other hand, should have the ability to grow at 35-37 °C temperature. Global warming could have a significant effect on fungal populations.
Global warming can change the distribution of heat-tolerant and susceptible species by favouring those that are more thermotolerant, US researchers Monica A Garcia-Solache and Arturo Casadevall had said in their 2010 paper Global Warming Will Bring New Fungal Diseases for Mammals.
This will facilitate fungi to spread and enter into closer contact with human populations and a few of those having pathogenic potential can acquire the ability to survive at body temperatures.
This threat is magnified as some fungi can take the benefit of a natural selection-adaptation strategy, and therefore adapt to a higher temperature by thermal selection.
Global warming means the narrowing of the thermal difference between the human body and its surroundings. Every degree increase in the global average temperature reduces this gradient by about five per cent. This increases the chance of the prevalence of fungal diseases.
Fungal infections are expected to pose a greater threat to human beings in the years to come due to rising temperatures, caused by climate change and other reasons such as growing resistance to the small number of treatments available.
Dibyendu Chaudhuri works with the research and advocacy unit of Professional Assistance for Development Action (PRADAN), a non-profit working in India
Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth
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