PATHOGENS IN LIVESTOCK WASTE, THEIR POTENTIAL FOR MOVEMENT THROUGH SOIL AND ENVIRONMENTAL-POLLUTION

Livestock wastes contain many pathogenic microorganisms including bact eria, viruses and protozoa. Following the application of these wastes to land the potential exists for environmental contamination. Plants, soil and ultimately water courses which may subsequently be used as ca tchments for public water supplies may all be affected. Research atten tion is now being focused on this possibility, especially in the case of protozoan pathogens which may be the most important as they are oft en resistant to current methods used in public water treatment. In thi s review we highlight some of the many factors that are likely to infl uence the degree of pollution by their effect on both the vertical and horizontal transport of microorganisms through soil. Soil pH, tempera ture, the presence of plants, microbial surface properties, type of wa ste, soil type and soil water content and flow may all affect the rate and extent of vertical transport, with the latter two generally consi dered to be the most important. Lateral movement is a particular probl em in soils with impermeable substrata or in waterlogged conditions an d in these cases the major factors affecting movement include rainfall rate, topography of the land and the rate at which microorganisms par tition into the runoff.