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

Risk factors, mortality, and predictors of survival in COVID-19-associated pulmonary mucormycosis: a multicentre retrospective study from India

OBJECTIVES

To compare COVID-19-associated pulmonary mucormycosis (CAPM) with COVID-19-associated rhino-orbital mucormycosis (CAROM), ascertain factors associated with CAPM among patients with COVID-19, and identify factors associated with 12-week mortality in CAPM.

METHODS

We performed a retrospective multicentre cohort study. All study participants had COVID-19. We enrolled CAPM, CAROM, and COVID-19 subjects without mucormycosis (controls; age-matched). We collected information on demography, predisposing factors, and details of COVID-19 illness. Univariable analysis was used to compare CAPM and CAROM. We used multivariable logistic regression to evaluate factors associated with CAPM (with hypoxemia during COVID-19 as the primary exposure) and at 12-week mortality.

RESULTS

We included 1724 cases (CAPM [n = 122], CAROM [n = 1602]) and 3911 controls. Male sex, renal transplantation, multimorbidity, neutrophil-lymphocyte ratio, intensive care admission, and cumulative glucocorticoid dose for COVID-19 were significantly higher in CAPM than in CAROM. On multivariable analysis, COVID-19-related hypoxemia (aOR, 2.384; 95% CI, 1.209-4.700), male sex, rural residence, diabetes mellitus, serum C-reactive protein, glucocorticoid, and zinc use during COVID-19 were independently associated with CAPM. CAPM reported a higher 12-week mortality than CAROM (56 of the 107 [52.3%] vs. 413 of the 1356 [30.5%]; p = 0.0001). Hypoxemia during COVID-19 (aOR [95% CI], 3.70 [1.34-10.25]) and Aspergillus co-infection (aOR [95% CI], 5.40 [1.23-23.64]) were independently associated with mortality in CAPM, whereas surgery was associated with better survival.

DISCUSSION

CAPM is a distinct entity with a higher mortality than CAROM. Hypoxemia during COVID-19 illness is associated with CAPM. COVID-19 hypoxemia and Aspergillus co-infection were associated with higher mortality in CAPM.

Association of COVID with Mycosis in General

BACKGROUND

The COVID-19 pandemic caused by SARS-CoV-2 is a respiratory disease which created havoc worldwide, was accompanied by another peculiar, otherwise rare, secondary fungal infection Mucormycosis which was observed at exceptionally high incidence in India during the second wave of COVID-19. The article explores possible links between the two infectious diseases to understand a higher-than-normal occurrence of Mucormycosis in COVID-19 patients. Coronavirus enters the patients through ACE-2 and many other receptors like- NRP-1, TfR, CD-126, and CD-26. Virus bind to cells possessing these receptors and affect their proper functioning, disturbing homeostatic metabolism and resulting in conditions like hyperglycemia, Diabetic Ketoacidosis (DKA), low serum pH, iron overload, anemia, hypoxia, and immunosuppression as explained in the article. All these outcomes provide a very supportive environment for the attack and spread of Mucormycosis fungi. The major receptor for Mucormycosis in humans is the GRP-78. Its expression is upregulated by coronavirus entry and by hyperferritinemia, hyperglycemia, and acidic conditions prevalent in COVID patients, thus providing an easy entry for the fungal species. Upregulation of GRP-78 furthermore damages pancreatic β-cells and intensifies hyperglycemia, showing quite a synergic relationship. Inordinate rise of Mucormycosis cases in India might be explained by facts like- India possessing a large proportion of diabetic patients, emergence of a very deadly strain of coronavirus- Delta strain, higher doses of steroids and antibodies used to treat patients against this strain, overburdened health care services, sudden much higher need of oxygen supply and use of industrial oxygen could explain the Mucormycosis outbreak observed in India during the second wave of COVID-19.

OBJECTIVE

The present review discusses the functional interdependence between COVID-19 and Mucormycosis and summarizes the possible synergic links between COVID and Mucormycosis.

CONCLUSION

The receptors and metabolic pathways affected by COVID-19 result in severe physiological conditions- hyperglycemia, DKA, anemia, iron overload, immunosuppression, and hypoxia. All these conditions not only increase the expression of GRP-78, the major receptor for entry of fungi but also play a crucial role in providing quality media for Mucormycosis fungus to establish and grow. Hence explains the fungal epidemic observed in India during the second wave of COVID-19 in India.

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

BACKGROUND

Factors associated with pulmonary mucormycosis (PM) among subjects with diabetes mellitus (DM) remain unclear. Following the coronavirus disease (COVID-19)-associated mucormycosis outbreak in India, specific environmental exposures (especially cattle dung exposure) were proposed as possible aetiology. We hypothesized that environmental factors are associated with PM. We compared subjects with DM with (cases) and without PM (controls).

METHODS

In this case-control study, for each PM case, we included five unmatched diabetic controls (hospital [n = 2], community [n = 3]) without PM. We collected information on demography, COVID-19 infection, glycated haemoglobin% (HbA1c), the type of house (pucca vs. kutcha) where the participants reside, and other environmental factors. The primary exposure tested was cattle dung exposure (CDE; using cattle dung cakes as fuel or cattle handling). We performed a multivariate logistic regression to explore factors associated with PM and report the association as an adjusted odds ratio (OR) with 95% confidence intervals (CI).

RESULTS

We enrolled 39 PM cases and 199 controls (hospital [n = 80], community [n = 119]). CDE (OR 0.68, 95% CI [0.14-3.31]; p = 0.63) was not associated with increased PM in DM. We found male sex (OR 4.07, 95% CI [1.16-14.31]), higher HbA1c (OR 1.51, 95% CI [1.18-16.32]), COVID-19 (OR 28.25, 95% CI [7.02-113.6]) and residence at kutcha house (OR 4.84, 95% CI [1.33-17.52]) associated with PM.

CONCLUSION

Cattle dung exposure was not associated with PM in subjects with DM. Instead, male sex, poor glycaemic control, COVID-19 and the type of housing were associated with pulmonary mucormycosis.

Epidemiology of COVID-19-Associated Mucormycosis

Purpose of the Review

To describe the epidemiology and risk factors for Coronavirus disease-19 (COVID-19)-associated mucormycosis (CAM) based on current published literature.

Recent Findings

COVID-19 is associated with an increased risk of secondary infections. Mucormycosis is an uncommon invasive fungal infection that typically affects people with immunocompromising conditions and uncontrolled diabetes. Treatment of mucormycosis is challenging and is associated with high mortality even with standard care. During the second wave of the COVID 19 pandemic, an abnormally high number of CAM cases were seen particularly in India. Several case series have attempted to describe the risk factors for CAM.

Summary

A common risk profile identified for CAM includes uncontrolled diabetes and treatment with steroids. COVID-19-induced immune dysregulation as well as some unique pandemic specific risk factors may have played a role.

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

We found inappropriate glucocorticoid therapy and zinc supplementation were significantly associated with these illnesses.

We performed a case–control study across 25 hospitals in India for the period of January–June 2021 to evaluate the reasons for an COVID-19–associated mucormycosis (CAM) outbreak. We investigated whether COVID-19 treatment practices (glucocorticoids, zinc, tocilizumab, and others) were associated with CAM. We included 1,733 cases of CAM and 3,911 age-matched COVID-19 controls. We found cumulative glucocorticoid dose (odds ratio [OR] 1.006, 95% CI 1.004–1.007) and zinc supplementation (OR 2.76, 95% CI 2.24–3.40), along with elevated C-reactive protein (OR 1.004, 95% CI 1.002–1.006), host factors (renal transplantation [OR 7.58, 95% CI 3.31–17.40], diabetes mellitus [OR 6.72, 95% CI 5.45–8.28], diabetic ketoacidosis during COVID-19 [OR 4.41, 95% CI 2.03–9.60]), and rural residence (OR 2.88, 95% CI 2.12–3.79), significantly associated with CAM. Mortality rate at 12 weeks was 32.2% (473/1,471). We emphasize the judicious use of COVID-19 therapies and optimal glycemic control to prevent CAM.