Bacterial populations in the river undergo huge loss in diversity but a steep increase in bacterial load when millions of people bathe at designated bathing sites during Kumbh Mela, a team of researchers has found. The loss in microbial diversity was nearly 37.5% while the increase in bacterial load was about 130-fold during the event.
The team led by Dr. Avinash Sharma from the National Centre for Cell Science, Pune, found that bacteria belonging to certain phyla reduced significantly while the prevalence of bacteria belonging to phylum Firmicutes (known to be also associated with human skin, stools and many infectious pathogens) was nearly 95%. The study was carried out in 2015 at five bathing sites in the Godavari River in Nashik and the results were published in the journal Microbial Ecology. Samples were collected prior to and during the Mela allowing the scientists to compare the spatiotemporal changes to water quality and bacterial communities.
Besides changes in bacterial diversity and load, the study found an increase in infectious diseases and drug-resistant microbes in the river water samples collected during the Mela. There were elevated levels of genes related to Helicobacter pylori, Salmonella and Staphylococcus aureus. Elevated levels of drug-resistant genes include antifolate resistance, beta-lactam resistance and vancomycin resistance, to name a few.
The water samples collected during the Kumbh Mela had much higher total dissolved solids and total suspended solids. The biological and chemical oxygen demand increased due to higher release of organic particles during the Mela compared with before the Mela. As a result, there was “substantial reduction” in the concentration of dissolved oxygen. “The substantial decrease in dissolved oxygen while the COD and BOD increased could be due to increased bacterial load in the water,” says Dr. Sharma.
While richness of bacterial species was higher upstream, at the bathing sites, the diversity dropped, and the bacterial community was dominated by few phyla. In all, 25 bacterial phyla were recorded and seven phyla (including Firmicutes) contributed to about 99% of the total bacterial diversity before the event. During the event, the diversity dropped by 37.5% and the diversity was restricted to just three phyla. The Fermicutes were the most abundant with over 90% at all the five bathing sites.
Though the diversity reduced, the bacterial load increased 130-fold in samples collected during the event. Skin and faecal microbiota increased 2.3-fold and 2.9-fold respectively during the gathering. “By comparing the water samples collected before and during the event, we found a huge increase in infectious disease and antimicrobial-resistant genes during the Mela. These genes could pose a serious threat to public health,” he says.
Compared with skin microbiota, the faecal microbiota is predominant at one sampling site. “This site is located upstream and is a remote location and not a major bathing site. Because of this, open defecation might be more prevalent. This is my guess. We are yet to do any scientific study to ascertain the cause,” Dr. Sharma says.
During the same study, the researchers discovered a new bacterium, which they named Corynebacterium godavarianum, that showed resistance to antibiotics like amoxycillin, augmentin, cefpodoxime and clindamycin. The discovery was published in the journal International Journal of Systematic and Evolutionary Microbiology.
“Our study highlights the need to create awareness among pilgrims to avoid open defecation and maintain personal hygiene to reduce the amount of microbes that get introduced into the river. A closed system for bathing prior to taking a dip in the river should be put in place to reduce contamination of human-associated skin bacteria,” says Kunal Jani from NCCS and first author of the paper.
Besides taking a dip in the river, pilgrims also drink the holy water. “Drinking this water containing infectious disease genes and antimicrobial-resistant genes could pose serious health issues. It might be preferable to drink the holy water much upstream where fewer people bathe,” he suggests.