Screening of the municipal water system of La Plata, Argentina, for human intestinal parasites

The La Plata River, though severely contaminated by intestinal parasites th rough the discharge of tons of crude fecal material from a main sewage chan nel, nevertheless provides drinking water to two-thirds of La Plata, Argent ina, after conventional purification at a processing plant. With intestinal parasitosis being endemic here, we investigated the importance of this wat er in transmitting such pathogens to the city's populace by means of standa rd methodology for sample acquisition and processing involving filter-conce ntration of waterborne particulates. Of 14 tap-water samples collected from the distribution network, 12 pertained to four zones (A-D) within the city center; while the remaining 2 were obtained near the processing plant, 15 kilometers outside the city. Although parasites were found within the sampl es derived from the four urban zones, none were detected in the specimens o btained near the plant. The four downtown areas differed from each other as to the quantity and nature of the parasites present in their water: wherea s zones A and B registered similar lower levels of contaminants, C and D ex hibited higher values significantly different from the former two and from each other. Given an average parasite count/l citywide of 0.38 and a probab ility of encountering a parasite within 11 of water of 0.32, the municipal network is seen to contribute to the transmission of intestinal parasites. A routine system of water-quality control is therefore needed throughout th e city along with the establishment of infrastructures for locating and eli minating peripheral sources of contamination.