Evaluation of Animal-specific Viral and Mitochondrial DNA Markers and Their Application to Microbial Source Tracking of Drinking Water Sources in the Kathmandu Valley, Nepal

摘要

This study evaluated the performances of animal-specific mitochondrial DNA (mtDNA) and viral markers and applied them to microbial source tracking (MST) of drinking water sources in the Kathmandu Valley, Nepal. Altogether, 122 previously collected composite fecal-source samples, including human sewage, feces of ruminants, pigs, dogs, chickens, and ducks, and manures of ruminants and chickens, were used for the evaluation of markers' performances. Water samples (n = 250) collected previously in 2016 were used for MST. Performances of ruminant-specific (Bovine-mtDNA), dog-specific (Dog-mtDNA), and pig-specific (Swine-mtDNA) mtDNA markers and chicken-specific (chicken parvoviruses (ChkPVs)), pig-specific (porcine adenoviruses (PoAdVs) and porcine teschoviruses), and ruminant-specific (bovine polyomaviruses and bovine noroviruses) viral markers were evaluated by quantitative PCR. All three tested mtDNA markers, ChkPVs, and PoAdVs were selected based on sensitivity, specificity, and accuracy for MST of water samples. Out of 250 water samples, bovine-, dog-, and swine-specific mtDNA markers were detected in 3 (1%), 6 (2%), and 3 (1%) samples, respectively. Chicken-specific markers were detected in 9% (9/97) of samples. The detection of animal-specific fecal markers in drinking water sources indicates high risks of transmission of zoonotic diseases. Thus, policy makers should focus on implementing suitable strategies for mitigating fecal pollution.