Use of a novel soil tilting table apparatus to demonstrate the horizontal and vertical movement of the protozoan pathogen Cryptosporidium parvum in soil

Abstract

A novel greenhouse based soil tilting table apparatus was used to investigate the potential for movement of the protozoan pathogen Cryptosporidium parvum both through and across a low permeability soil following the application of contaminated livestock waste to land. Soil blocks supported at an angle of 7.5% by the soil table were inoculated at one end with oocyst seeded slurry and subsequently irrigated at regular intervals over a 70-day period. Movement of the pathogen in runoff was demonstrated for at least 21 days and in one case in excess of 70 days from the time of inoculation. Water was also lost following percolation down through the soil profile and significant numbers of oocysts were also lost via this route, average numbers leached decreasing from 8.36±0.56×10⁶ at day 1 to 2.27±0.73×10⁴ at day 70. At the end of the study cores were removed from the soil blocks to determine the location of oocysts remaining within the soil. Numbers decreased down through the soil profile and as the distance from the point of inoculation increased so that 70 cm from the point of inoculation no oocysts could be detected in the soil at any depth. This implies that oocysts contained in runoff stay in the aqueous phase and do not precipitate out onto the soil surface, suggesting that even if the distances travelled are increased there may still be a significant pollution threat.