Cow dung drying on a wall before it can be used as a cooking fuel. Photo: Dennis Jarvis/Wikimedia Commons, CC BY-SA 2.0
- The 2021 black fungus epidemic in India has been linked to the irrational use of steroids to treat COVID-19 patients with diabetes, among other causes.
- A new article by a group of scientists argues that burning cow dung could be another possible cause, as it releases fungal spores into the air.
- A mucormycosis infection is caused by fungi of the order Mucorales. These fungi thrive in the excrement of herbivores – including cows.
- If this is true, politico-religious rhetoric around burning cow dung in ‘havans’ could also have contributed to the problem.
Bengaluru: Burning cow dung could have encouraged the sharp rise in black fungus cases in India, according to an article published in the journal Environmental Microbiology on March 31.
The Indian government declared black fungus, technically called mucormycosis, an epidemic during India’s second COVID-19 wave. At this time, the country recorded 51,775 cases of the fungal infection and accounted for 71% of the global case load.
Black fungus infections have a mortality rate of 54%. During the second wave, the chief of the All India Institute of Medical Sciences, New Delhi, Dr Randeep Guleria, linked the higher incidence of black-fungus cases in India to the “misuse of steroids”. Some studies, like this one, have come to the same conclusion.
This said, India’s black fungus burden has always been high, even before COVID-19: it has accounted for 65,000 deaths every year on average.
In the new article, researchers from the US and India proposed an additional cause of India’s big black fungus spike towards the second half of its second wave. They have postulated a link between the higher number of black fungus cases and a heightened number of fungal spores in the air.
A mucormycosis infection is caused by fungi of the order Mucorales. These fungi thrive in the excrement of herbivores – including cows. There is an abundant amount of cow dung in India thanks to its 300 million cattle.
Also read: India Doctors Warn Against Cow Dung as COVID-19 Cure
Jessy Skaria, an author of the article and an independent researcher in the US, told SciDevNet that his team wanted to understand why there were so many more black fungus cases in India than in other countries. Team members wrote that when cow dung cakes are burnt, as fuel in poorer households, e.g., they scatter fungal spores into the air, where they’re moved around by winds.
“The fungus can remain in the nose without causing issues. When there is a provocation like diabetes, plus COVID, plus steroids, it could flare up,” noted virologist Jacob John told the New Indian Express. “This does not mean cow dung exposure is the direct cause of the illness.”
To be sure, to date, researchers haven’t been able to ascertain the precise cause of the black fungus spike around mid-2020 in India. The various possibilities they have advanced include “poor glycaemic control and inappropriate steroid therapy”; more spores in the air; contaminated oxygen supplies, respiratory equipment and/or humidifier water; reused face masks; and zinc supplements.
The authors of the new article wrote that the relatively more widespread use of fuel derived from herbivore excrement could have been another contributor.
It’s well-known that burning cow dung releases fungal spores into the air. To this end, the researchers also wrote that political and religious rhetoric in the last two years could have exacerbated the issue in India. A 2020 paper – authored, among others, by a scientist of the Indian Council of Medical Research – recommended “Vedic fire ceremonies” to kill viruses in the air. Many people have conducted such ceremonies around the country, often led by BJP leaders.
Another source of these spores could have been crematoria that ran out of wood while burning bodies of people who had died of COVID-19 during the second wave, and began to use cow dung instead.
The authors also described a correlation between the use of cow dung in different parts of the country and the relative prevalence of black fungus cases there.
“Notable exceptions are Kerala and West Bengal, where the incidence of mucormycosis was far lower than in Maharashtra and Gujarat, where the slaughter of cattle is strictly banned and where the use of cow excreta for fuels and rituals is popular,” Skaria told SciDevNet. “It’s hugely pertinent that in Kerala, where there is no ban on slaughtering cows and no taboo on eating beef … and where cow dung is almost never used as fuel … the incidence of mucormycosis was found to be low.”
Also read: US Customs to Indian Travellers: Don’t Carry Cow Dung in Your Luggage
The research team cited examples of other countries like Iran, which reported unusually more mucormycosis cases than many other similar countries. The team linked this to the donkey dung that locals burned to derive a traditional remedy for COVID-19.
“Verifying our hypothesis could have important implications for the prevention of [COVID-associated mucormycosis], and mucormycosis in general, in India and worldwide,” the team wrote in its article. “Further research in these directions would hopefully establish the role of herbivore dung in the causation … and lay the foundation for initiating measures to reduce the incidence of the disease.”
Judy Stone, a US-based infectious disease and clinical research specialist, wasn’t involved in the article. Speaking to SciDevNet, she called the hypothesis – that burning more cow dung could have played a part in triggering India’s black-fungus surge – “a very plausible hypothesis”. She also said she hoped the idea could prompt “further study by aerobiologists and other scientists in India”.
Aditi Murti is an intern at The Wire Science.