by Natalie Creekmur
The quality of drinking water in the densely populated city of is a major concern. The Kathmandu region is home to an endemic of typhoid fever, a disease that causes a severe systemic infection in the human body. The bacterial pathogens that cause typhoid fever are Salmonella Typhi (S. Typhi) and Salmonella Paratyphi A (S. Paratyphi A). It is generally accepted that these two types of bacteria are transmitted via ingestion of contaminated food and drinking water or via human-to-human contact. In Kathamandu, the main water sources for the population are gravity-dependent stone waterspouts. The rainfall and snowmelt that sustain the waterspouts collect in soft-rock aquifers that act as natural reservoirs. This water is untreated and vulnerable to contamination. As a result, the areas surrounding the stone waterspouts experience increased S. Typhi and S. Paratyphi A infections in the population.
To assess the public health risks of various water sources and the ecology of drinking water in Kathmandu, Karkey et. al. (2016) analyzed the bacterial contamination, chemical composition, and ecological dynamics in the water supply. For a year, weekly water samples were collected from 10 different locations that included stone waterspouts, sunken wells, and piped supplies. Physical and chemical analyses were conducted using various means of data acquisition such as thermometers, conductivity meters, and spectrophotometers. In addition, microbiological and molecular analyses were conducted. Bacterial culturing on agar plates was performed, followed by bacterial identification. DNA samples were collected and polymerase chain reactions identified the DNA sequences that are specific to S. Typhi and S. Paratyphi A.
The sustained contamination of nitrites, nitrates, and chloride found from the chemical analyses was alarming. These chemicals are markers of sewage and fecal contamination. Bacterial markers such as coliforms were also found in the drinking water samples. Coliforms are bacteria present in feces and are good indicators of water contamination. Among all locations, S. Typhi and S. Paratyphi A were present in equal amounts. 16S rRNA gene surveying was conducted to assess bacterial diversity. The results of this showed that ecological factors, such as the proximity of sewages pipes, affect the bacterial makeup for different water sources.
The research conducted by Karkey et. al. (2016) revealed much about drinking water quality and contamination. While there is seasonal variation for the amount of contaminants and pollutants, there is a year round fecal contamination level that exceeds World Health Organization standards. The risk for disease in Kathmandu is severe, especially when more than 20% of water users attain their water from highly contaminated stone waterspouts. The next steps for typhoid fever intervention in Kathmandu would be to advocate for in-home filters and sterilization systems. The long-term aim for disease reduction in this region is the improvement of sewage and water systems.
Abhilasha Karkey, Thibaut Jombart, Alan W. Walker, Corinne N. Thompson, Andres Torres, Sabina Dongol, Nga Tran Vu Thieu, Duy Pham Thanh, Dung Tran Thi Ngoc, Phat Voong Vinh, Andrew C. Singer, Julian Parkhill, Guy Thwaites,
Buddha Basnyat, Neil Ferguson, Stephen Baker. 2016. The Ecological Dynamics of Fecal Contamination and Salmonella Typhi and Salmonella Paratyphi A in Municipal Kathmandu Drinking Water. PLOS Neglected Tropical Diseases. 10 (1). 1-18.