The Distribution of Fecal Contamination in an Urbanized Tropical Lake and Incidence of Acute Diarrheal Disease

Abstract

Aquatic ecosystems of tropical countries are vulnerable to fecal contamination that could cause spikes in the incidences of acute diarrheal disease (ADD) and challenge public health management systems. Vembanad lake, situated along the southwest coast of India, was monitored for one year (2018−2019). Escherichia coli, an indicator of fecal contamination, was prevalent in the lake throughout the year. Multiple antibiotic resistance among more than 50% of the E. coli isolates adds urgency to the need to control this contamination. The high abundance of E. coli and incidence of ADD were recorded during the early phase of the southwest monsoon (June−July), prior to the once-in-a-century floods that affected the region in the later phase (August). The extent of inundation in the low-lying areas peaked in August, but E. coli in the water peaked in July, suggesting that contamination occurred even prior to extreme flooding. During the COVID-19-related lockdown in March−May 2021, fecal contamination in the lake and incidence of ADD reached minimum values. These results indicate the need for improving sewage treatment facilities and city planning in flood-prone areas to avoid the mixing of septic sewage with natural waters during extreme climate events or even during the normal monsoon.

Using Multi-Spectral Remote Sensing for Flood Mapping: A Case Study in Lake Vembanad, India

“…While there are limitations in the applicability of multi-spectral visible radiometry under cloudy conditions, the use of Sentinel-2 and other MSI sensors can increase the temporal coverage of flood maps considerably, even if only partial maps are available. Additional benefits lie in the application of multi-spectral observations for water quality monitoring [10][11][12]55]. Recent work has indicated that heavy rains and floods are tied to the dynamics of microbial pollutants in the water, including pathogenic bacteria such as Vibrio cholerae and Escherichia coli [11,12].…”

“…Additional benefits lie in the application of multi-spectral observations for water quality monitoring [10][11][12]55]. Recent work has indicated that heavy rains and floods are tied to the dynamics of microbial pollutants in the water, including pathogenic bacteria such as Vibrio cholerae and Escherichia coli [11,12]. Therefore, it becomes important that mitigation measures include steps to prevent outbreaks of waterborne diseases.…”

“…The development of wetland agriculture has led to substantial changes in the hydrology of Lake Vembanad with consequences for both water quality and wetland functions, such as the ability to regulate floods [5,6,8]. Additional pressures from domestic waste and sewage, industrial pollution, eutrophication, and aquatic weed infestation [5,6] have degraded the ecosystem in Lake Vembanad, and the region is now considered one of the most polluted estuaries in India with high levels of suspended and dissolved matter, and prevalence of pathogenic bacteria [9][10][11][12].…”