Do we really need to worry about mold fungi?
Fungus, a word that has been reiterated in the national and international newspapers since the onset of black fungus in India in March 2021. The subsequent appearance of white fungus and yellow fungus is not the end of fungal cases in humans. Rather, very recently, the green fungus has been reported in India in a post-covid patient. Considering the number of fungal cases, black fungus placed number one because it has affected more than 31,000 people and claimed at least 2,100 lives in India to date.
The BIRDEM hospital has reported few black fungus cases in post-covid patients and no other fungal cases in Bangladesh. At the very outset of growing concern about fungus, we should know a few important information about the meaning of fungus, its distribution, and functions.
Basically, fungus is an eukaryotic organism whose cell wall is composed mainly of chitin, glucans, and glycoproteins. It was previously considered under plant group but now placed individually in its own kingdom 'Fungi'. There are innumerable fungal species available in nature. Mycologists predict the number could be 1.5 million of which 100,000 species have been described in the literature. They are present in every ecological niche. As an omnipresent organism, we can not think about our life without fungi. Our life would not be functioning if fungi absent in nature. Why? Because they are the dominant decomposers in our ecosystem and they are recycling the nutrients in all terrestrial habitats.
Interestingly, recent occurrence of fungi in post-covid patients are actually mold fungi. These molds are black fungus (Rhizopus and Mucor), white fungus (Candida and Aspergillus), yellow fungus (Chroysosporium) and green fungus (Aspergillus). Molds also cause other human diseases like asthma and allergy. They can also produce mycotoxins (i.e., toxins produced by fungi) having carcinogenic, teratogenic, and neurotoxic properties.
A single mold fungus can produce 40 or more proteins that have allergic properties. But, before being panicked about mold, we should know that they are able to grow at our home. For instance, if you leave some breads and biscuits for couple of days then you will be witnessed some powdery bits grow onto the surface of your breads and biscuits. Likewise, leaving some strawberries for few days on dining table or even in the refrigerator one can see white to gray cottony mass growing on the fruits.
These are nothing but mold fungi. They are ubiquitous fungal species having diverse lifestyles including saprophytic, opportunistic and pathogenic. There are thousands of known mold species which live in close association with plants, animals, and human beings. But molds don't only cause diseases in human and plants, they can be beneficial too. For example, molds are used in the food processing industry (such as cheese, bread, sausage, soy sauce, alcoholic beverages) and to produce antibiotics (penicillin, cyclosporine, lovastatin).
Humans are not the only host of mold fungi. As a plant pathologist, I could give you scores of examples of mold cases in both standing crops and post-harvest fruits and vegetables. Molds in plants are blue mold (Penicillium expansum); one of the most common and economically important postharvest fungicausing extensive fruit rot disease in the world; gray mold (Botrytis cinerea) of grapes, apple, and pear; green mold (P. digitatum) of orange; black mold (Aspergillus niger) of onion and garlic; sooty mold (Capnodiumcitri), and white mold (Sclerotinia sclerotiorum) of potato. The grain mold (Aspergillus flavus) could produce aflatoxin--a mycotoxin in grains such as corn, peanuts, sorghum, sunflower, and wheat. The main concern of aflatoxin is its poisonous carcinogenic and mutagenic properties.
The infamous incident in Europe since nineteenth century was "Great Irish Famine" due to the outbreak of late blight of potato, the causal organism is Phytophthora infestans--a slime mold. About 1 million people died and more than a million fled the country. The disease was so severe that it completely changed the Ireland's demographic, socio-economic, political and cultural perspective.
Now, let's discuss about some false rumors about mold fungi on social media. A Facebook post got viral which was claiming black fungus inside the refrigerator and black spore masses were seen on the surfaces of onion. These black spores are nothing but the spores of black mold (Aspergillus niger) which are very common post-harvest pathogens in both onion and garlic. They are very unlikely to cause human illness. This pathogen has been labelled with generally recognized as safe (GRAS) from the US Food and Drug Administration (FDA). Meanwhile, this mold may produce some mycotoxins (such as, fumonisins andochratoxins); therefore, it is advisable to wash onion and garlic thoroughly before human consumption.
Going back to the context of headline, we should be cautious and careful but not be worried. Because we can not completely eradicate mold fungi from our nature. As a precautionary measure, a very strict quarantine policy should be imposed so that no mold-bearing foreigner could enter the country. Likewise, strict plant quarantine measures should be applied in all the borders so that no foreign plant products with mold fungi could enter into the country.
At personal level, as molds are spreading through the air therefore, proper social distance maintenance, sanitation, hygiene and wearing mask are imperative measures to keep people away from mold fungi. Moreover, immune system is to be boosted through regular exercise, adequate sleep, and healthy diet. Based on the existing scientific literature, except the immunosuppressed patients, mold fungi are less likely to cause serious harm to humans. One of the best measures to avoid molds from plant products is to store them in a clean place where there is free-flowing air and ample light.
To sum up, the emergence of mold fungi in human gives a cautionary signal that the fungi may resurge with its full potentiality in near future. Therefore, an extensive research on the biology, ecology, species diversity and pathogenicity of mold fungi in both plants and humans is urgent to find a solution against the mold menace.
Dr Md Abdullahil Baki Bhuiyan, Associate Professor, Department of
Plant Pathology, BSMRAU