Identification of Human and Animal Fecal Contamination in Drinking Water Sources in the Kathmandu Valley, Nepal, Using Host-Associated Bacteroidales Quantitative PCR Assays

Abstract

This study identified the sources of fecal contamination in the groundwater of different land covers. A total of 300 groundwater samples were collected in the Kathmandu Valley, Nepal, in the dry (n = 152) and wet (n = 148) seasons of 2016. Fecal indicator bacteria were initially enumerated, and then fecal contamination sources were identified using human (BacHum), ruminant (BacR), and pig-associated (Pig2Bac) Bacteroidales quantitative polymerase chain reaction assays. Sixty-six percent (197/300) of the tested groundwater samples had Escherichia coli concentrations higher than the World Health Organization threshold for drinking (<1 most probable number/100 mL). The fecal contamination of the groundwater was of human (22%, 55/250), ruminant (11%, 28/250), and pig (3%, 8/250) origin. Deep tube wells were less likely to be positive for E. coli and fecal markers compared to shallow dug wells. The human fecal marker was more likely to be detected in sources from built-up as compared to agricultural areas (Adjusted odds ratio (AOR) = 3.60, p = 0.002). Likewise, the ruminant fecal marker was more likely to be detected in sources from agricultural as compared to built-up areas (AOR = 2.90, p = 0.018). These findings suggest the preparation of mitigation strategies for controlling fecal pollution based on land cover and well types.

Bioindicadores alternativos da qualidade da água para consumo humano

“…Quanto ao período de publicação dos artigos, 1 foi publicado em 2009 (Copeland et al, 2009), 2 (18,2%) em 2014 (Krolik et al, 2014;Nescerecka et al, 2014), 3 (27,3%) em 2015 (Bianco et al, 2015;Rodrigues et al, 2015;Sorensen et al, 2015), 3 (27,3%) em 2016 (Odagiri et al, 2016;Giglio et al;Weiss et al; e 2 estudos (18,2%) em 2018 (Diston et al, 2018;Malla et al, 2018).…”

“…Das publicações selecionadas, 3 (27,3%) tiveram como local de estudo o Brasil (Copeland et al, 2009;Bianco et al, 2015;Rodrigues et al, 2015), e quanto aos demais artigos, os estudos ocorreram no Canadá (Krolik et al, 2014), Letônia (Nescerecka et al, 2014), Zâmbia Research, Society and Development, v. 9, n. 9, e51996824, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i9.6824 8 (Sorensen et al, 2015), Índia (Odagiri et al, 2016), Itália (Giglio et al;, Nicarágua (Weiss et al;, Suíça (Diston et al, 2018) e Nepal (Malla et al, 2018 Quanto ao biomarcador utilizado, 5 (45,4 %) dos estudos selecionados utilizaram apenas bactérias (Krolik et al, 2014;Bianco et al, 2015;Sorensen et al, 2015;Giglio et al;Weiss et al;Malla et al, 2018), 2 (18,2%) bactérias e vírus (Rodrigues et al, 2015;Diston et al, 2018), 1 (9,1%) bactérias, vírus e protozoários (Odagiri et al, 2016), 1 estudo utilizou bactérias e arqueas (Bianco et al, 2015), 1 estudo utilizou bactérias, protozoários e Imunoglobulina humana (Copeland et al, 2009), e outro, bactérias e ATP (Nescerecka et al, 2014).…”

“…A contagem de bactérias heterotróficas demonstrou altos níveis de contaminação. (Malla et al, 2018) E. coli e coliformes totais foram detectados em 66% e 94% das amostras, respectivamente. As taxas de detecção dos marcadores Bacteroidales de humanos, ruminantes e suínos foram 22%, 11% e 3%, respectivamente.…”

“…Segundo os tipos de amostras de água para consumo humano analisadas: 6 (54,5%) eram provenientes de captação subterrânea (Krolik et al, 2014;Sorensen et al, 2015;Giglio et al;Weiss et al;Diston et al, 2018;Malla et al, 2018), 2 (18,2%) de captação superficial (Bianco et al, 2015;Rodrigues et al, 2015), 1 de captação mista (Odagiri et al, 2016) (superficial e subterrânea), 1 da saída do tratamento e do sistema de distribuição (Nescerecka et al, 2014) e 1 de captação subterrânea, sistema de distribuição e armazenamento intradomiciliar (Copeland et al, 2009).…”

Study of Compliance of Sealed Bottled Water with Nepal Drinking Water Quality Standard: A Case of Bhaktapur Municipality, Nepal

“…Therefore, people in the Kathmandu valley depend upon underground water sources like shallow tube well, dug well and deep boring as the supplementary sources to fulfil their water demand. However, both the city and underground water sources are contaminated with biological agents (Diwakar, et al, 2008;Shrestha, et al, 2013;Malla, et al, 2018). Sewage lines, septic tanks, open pit toilets, leaching from landfill sites direct disposal of domestic and industrial waste are the causes of deterioration of ground water quality in Kathmandu valley (Pradhanang, et al, 2012).…”