Fecal contamination of drinking water supplies in and around Chandigarh and correlation with acute gastroenteritis.

Acute gastroenteritis due to Vibrio cholerae and Enterotoxigenic E. coli is a common problem faced in the hot and humid summer months in north India. The study was undertaken to evaluate drinking water supplies for fecal coliforms, V. cholerae and Enterotoxigenic E. coli in urban, semiurban and rural areas in and around Chandigarh and correlate with occurrence of acute gastroenteritis occurring from the same region. Drinking water sample were collected from various sources from April to October 2004 from a defined area. Samples were tested for fecal coliforms and E. coli count. E. coli were screened for heat labile toxin (LT) also. Stool samples from cases of acute gastroenteritis from the same region and time were collected and processed for V. cholerae, Enterotoxigenic E. coli (ETEC) and others like Salmonella, Shigella and Aeromonas spp. A total of 364 water samples were collected, (251 semi urban, 41 rural and 72 from urban areas). 116 (31.8%) samples were contaminated with fecal coliforms (58.5% rural, 33.4% semiurban and 11.1% of samples from urban areas). E. coli were grown from 58 samples. Ninety two isolates of E. coli were tested for enterotoxins of which 8 and 24 were positive for LT and ST respectively. V. cholerae were isolated from 2 samples during the outbreak investigation. Stored water samples showed a significantly higher level of contamination and most of Enterotoxigenic E. coli were isolated from stored water samples. A total of 780 acute gastroenteritis cases occurred; 445 from semiurban, 265 rural and 70 from urban areas. Out of 189 stool samples submitted, ETEC were the commonest (30%) followed by V. cholerae (19%), Shigellae (8.4%), Salmonellae (2.1%) and Aeromonas (2.6%). ST-ETEC (40/57) were commoner than LT-ETEC (17/57). In the present study, high levels of contamination of drinking water supplies (32.1%) correlated well with cases of acute gastroenteritis. Majority of cases of acute gastroenteritis occurred in the semi urban corresponding with high level of contamination (33.4%). The highest level of water contamination was seen in rural areas (58.5%) but the number of acute gastroenteritis cases were lesser (33.9%) as ponds were infrequently used for drinking purpose. Safer household water storage and treatment is recommended to prevent acute gastroenteritis, together with point-of-use water quality monitoring.