Could cattle dung burning have contributed to the epidemic of COVID-19-associated mucormycosis in India? Results of an experimental aero-mycological study.

ABSTRACT

BACKGROUND: Several hypotheses have been proposed for explaining the outbreak of coronavirus disease 2019 (COVID-19)-associated mucormycosis in India, including the burning of cattle dung cakes, though no study has yet been conducted to support this claim. METHODS: We conducted an aero-mycological study to evaluate whether Mucorales in the air increased during or after burning cattle dung cakes. We further compared the growth of Mucorales in the indoor air samples from houses with and without cattle. We also cultured fresh and dried cattle dung and soil samples for Mucorales. RESULTS: We noted no significant difference in the proportion of air samples growing Mucorales during (4/22 [18.2%]) and after (3/2 [13.6%]) cattle dung burning than that collected immediately before (4/22 [18.2%]). Mucorales were isolated in 15.4% of the indoor air samples obtained from different houses (both rural and urban); the proportion of samples growing Mucorales was not significantly different in households with and without cattle. We also observed growth of Mucorales in 6 of the 8 [75%] fresh and 3 of the 6 [50%] dried dung samples. The most common Mucorales isolated from soil and dung samples was Lichtheimia corymbifera, while Rhizopus arrhizus was the most common species isolated from indoor air samples. CONCLUSIONS: We found no significant increase in the proportion of air samples growing Mucorales during or after burning cattle dung cake than that before. It seems unlikely that cattle dung burning contributes to the occurrence of mucormycosis.