Contents lists available at ScienceDirect International Journal of Hygiene and Environmental Health journal homepage: www.elsevier.com/locate/ijheh Human and animal microbial source tracking in a tropical river with multiple land use activities Akechai Kongprajug a , Natcha Chyerochana a , Pornjira Somnark b , Pinida Leelapanang Kampaengthong c , Skorn Mongkolsuk a,d , Kwanrawee Sirikanchana a,d,* a Research Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, 10210, Thailand b Applied Biological Sciences, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok, 10210, Thailand c Water Quality Management Bureau, Pollution Control Department, Ministry of Natural Resources and Environment, Bangkok, 10400, Thailand d Center of Excellence on Environmental Health and Toxicology, CHE, Ministry of Education, Bangkok, 10400, Thailand ARTICLE INFO Keywords: Water quality monitoring Fecal indicators Microbial source tracking Bacteroidales PCR qPCR ABSTRACT The enhancement and restoration of the water quality of deteriorating surface water resources can be chal- lenging, particularly for rivers with multiple usages, such as agriculture, animal husbandry, human residence, and industries. Recently, the performance of DNA-based microbial source tracking (MST) indicators detected by end-point and quantitative PCR assays for identifying sources of fecal pollution from human sewage, swine, and cattle and non-host-specific (universal) fecal pollution in the Tha Chin River basin, Thailand, was evaluated. The present study monitored these validated MST markers and various physicochemical and microbial water quality parameters in samples collected from twelve stations along the Tha Chin River during four sampling events in the wet and dry seasons. No significant difference in precipitation was observed between the wet and dry samplings. Universal markers (both PCR and qPCR) were detected in all 48 samples, indicating persistent and continuing fecal contamination. The sewage- and swine-specific qPCR marker concentrations did not vary among the sampling events, whereas cattle-specific qPCR markers were detected only in the wet season. Animal- specific markers were detected in the lower Tha Chin River section, which is characterized by intensive animal farming. Sewage-specific markers were also found in the lower section and near an upstream residential area. The high agreement (87.5–100%) between the PCR and qPCR results suggested that PCR could serve as a lower- cost MST screening test that requires less technical expertise. A multivariate analysis conducted using the sur- vival analysis procedure to include censored data also emphasized the high pollution in the lower section of the river at all sampling events. Universal and swine-specific markers showed moderate correlations with microbial indicators, including total coliforms, fecal coliforms, E. coli, and enterococci. None of the MST markers or mi- crobial parameters were associated with the measured physicochemical parameters. This study provides the first evaluation of MST markers for monitoring surface freshwater in Thailand, and the findings might aid the pol- lution surveillance of impaired water bodies and the development of strategies for improving their water quality. 1. Introduction Population growth and economic development could lead to the expansion of human residential areas and the intensification of animal farming and other industries. These anthropological activities con- tribute significantly to pollution loads, which could be discharged ei- ther directly or indirectly into recipient bodies of water. The problem of water pollution is aggravated by the inadequacy of sanitation and wastewater facilities and the inefficiency of water governance and law enforcement (Pollution Control Department (PCD), 2018). The carrying capacity of a river is thus often exceeded, resulting in the river's inability to return to a natural state. Catchment disturbance, comprising four stressors that threaten water security—cropland, impervious sur- faces, livestock density, and wetland disconnectivity—clearly reflects the impact of land use on the health of river systems (Vorosmarty et al., 2010). These crucial underlying factors, including the river health index, have been emphasized in the evaluation criteria for the assess- ment of environmental water security in the Asia and Pacific region (Asian Development Bank, 2016). To expedite an abatement of water quality degradation, it is vital to accurately characterize connections between pollution loads and their originating sources. There are generally two types of pollution sources: https://doi.org/10.1016/j.ijheh.2019.01.005 Received 27 October 2018; Received in revised form 26 December 2018; Accepted 17 January 2019 * Corresponding author. Research Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, 10210, Thailand. E-mail address: kwanrawee@cri.or.th (K. Sirikanchana). International Journal of Hygiene and Environmental Health xxx (xxxx) xxx–xxx 1438-4639/ © 2019 Elsevier GmbH. All rights reserved. Please cite this article as: Kongprajug, A., International Journal of Hygiene and Environmental Health, https://doi.org/10.1016/j.ijheh.2019.01.005