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.

Multicenter Case–Control Study of COVID-19–Associated Mucormycosis Outbreak, India

“…Nonetheless, we provide weak indirect evidence implicating the severity of COVID-19 illness (elevated C-reactive protein) in the development of CAM. Finally, rural residence was significantly associated with CAM and might be attributed to higher levels of fungal spores in the rural environment (23)(24)(25)(26).…”

“…Based on a few media reports, 1 review hypothesized that the burning of cow dung led to the mucormycosis outbreak in India (27). However, a recent experimental aeromycological study found no evidence for this theory (25). Several case-control studies (n = 13) have assessed the risk factors associated with CAM (Appendix Table 8) (6,7,20,21,(28)(29)(30)(31)(32)(33)(34)(35)(36).…”

“…Based on a few media reports, 1 review hypothesized that the burning of cow dung led to the mucormycosis outbreak in India ( 27 ). However, a recent experimental aeromycological study found no evidence for this theory ( 25 ).…”

Risk factors for pulmonary mucormycosis in subjects with diabetes mellitus—A case‐control study

“…For instance, we observed a significantly smaller proportion of community controls (3%) on insulin therapy than those at the hospital (39%; 17 Further, a recent aero-mycological study found no association between the burning of cattle dung cake and Mucoralean spore burden in the ambient air. 18 The aero-mycological study, however, did not include any patient data. The current study disproved the cattle dung hypothesis and identified poor control of diabetes (higher glycated haemoglobin) and other factors associated with PM in DM.…”

Epidemiology of COVID-19–Associated Mucormycosis

“…The use of cow-dung to treat COVID-19 or the burning of cow-dung cakes causing spore dispersal and increased risk of CAM was postulated as a risk. However, there was no change in growth of Mucorales in air samples collected before and after cattle dung burning in an aero-mycological study done in India during the COVID-19 period [ 78 ].…”