Overland and near-surface transport of Cryptosporidium parvum from vegetated and nonvegetated surfaces.

Understanding microbial pathogen transport patterns in overland flow is important for developing best management practices for limiting microbial transport to water resources. Knowledge about the effectiveness of vegetative filter strips (VFS) to reduce pathogen transport from livestock confinement areas is limited. In this study, overland and near-surface transport of Cryptosporidium parvum has been investigated. Effects of land slopes, vegetation, and rainfall intensities on oocyst transport were examined using a tilting soil chamber with two compartments, one with bare ground and the other with brome (Bromus inermis Leyss.) vegetation. Three slope conditions (1.5, 3.0, and 4.5%) were used in conjunction with two rainfall intensities (25.4 and 63.5 mm/h) for 44 min using a rainfall simulator. The vegetative surface was very effective in reducing C. parvum in surface runoff. For the 25.4 mm/h rainfall, the total percent recovery of oocysts in overland flow from the VFS varied from 0.6 to 1.7%, while those from the bare ground condition varied from 4.4 to 14.5%. For the 63.5 mm/h rainfall, the recovery percentages of oocysts varied from 0.8 to 27.2% from the VFS, and 5.3 to 59% from bare-ground conditions. For all slopes and rainfall intensities, the total (combining both surface and near-surface) recovery of C. parvum oocysts was considerably less from the vegetated surface than those from the bare-ground conditions. These results indicate that the VFS can be a best management practice for controlling C. parvum in runoff from animal production facilities.