A large-scale study of bacterial contamination of drinking water and its public health impact in Nepal.

Bacterial contamination of drinking water is a major public health in Nepal. A large scale study on contamination of drinking water was done covering all three ecological belts (mountain, hill and Terai) in all five (eastern, central, western, mid-western and far-western) development regions of Nepal during 2009-2011. Of the total 506 water samples studied, one-forth (25.1%; 127/506) were visually turbid. Bacteriologically, 88.5% (448/506) samples were positive for total coliform (TC) whereas 56.5% (286/506) were positive for fecal coliform (FC) (Esch. coli). The TC positive rate ranged from 53.8% in Damak (Jhapa) to 100.0% in different districts. The FC positive rate varied more widely ranging from 10.0% in Bharatpur City (Chitawan) to 100.0% in Baglung Township (Baglung) with over 50.0% in most of the districts (over 75.0% in eight districts). Both TC and FC positive rate were highest in Far-western Development Region (DR). High TC positive rate (96.7%) in Far-western DR was followed by Western DR (93.9%), Eastern DR (89.2%), Central DR (87.0%) and Mid-western DR (74.6%). Highest FC positive rate (65.5%) in Far-western DR was followed by Med-western DR (63.5%), Western DR (55.9%), Central DR (53.2%) and Eastern DR (52.0%). TC positive was highest (90.7%) in hills followed by mountain (89.7%) and Terai (plain) (84.1%) belt. In contrast, FC positive rate was highest (66.2%) in mountain, followed by hills (58.0%) and Terai (49.7%). Of the total 506, 335 were piped tap water, 129 were boring water, 16 natural tap (spout), 16 were well (sallow/deep well) and 10 were mineral/uroguard treated water. TC positive rate was very high (81.2% to 100.0%) in different type water samples (piped tap: 90.1%; boring water: 85.2%; natural spout/tap: 81.2%; well water 100.0% and mineral water/uroguard treated water: 80.0%). FC positive rate ranged from 0.0% in mineral water/uroguard treated water to 93.7% in well water samples. These findings are of serious public health concern with regard to both endemicity and outbreak of waterborne diseases in the country.