Bacterial Pollution from Agricultural Sources: A Review

T potential for environmental contamination through the indiscriminate handling of agricultural wastes has been a topic of intensive research during the past two decades. The potential for disease transmission is the major bacteriological problem where public health is concerned. Bacterial pollution of the soil through land application of manures and sludges can also affect the indigenous soil populations and change the decomposition and nutrient recycling rates (Doran, 1979). More than twenty diseases have been identified as possibly transferred from animal manures (Azevedo and Stout, 1974). Several reviews have been written dealing with the health aspects of waste application (Sagik and Sorber, 1978; Menzies, 1977; Burge and Marsh, 1978; Diesch, 1970; Weaver et al., 1978; Dunlop, 1976; Strauch, 1976; Rankin and Taylor, 1969). Land application of wastes may spread disease via several pathways. Few disease outbreaks have been caused by bacteria of livestock origin but this possibility was shown by Jack and Hepper (1969) where salmonellosis mortality was traced to seepage from a slurry tank overflow. Rankin and Taylor (1969), studying dairy manure slurry, found several different species of bacterial pathogens in samples from various farms. Beef feedlot runoff has been shown to contain Salmonella infantis in an investigation by Miner et al. (1967). Historically, bacterial indicators have been used to monitor the pollution of surface and ground waters from domestic and animal sources. Total coliforms are used to monitor treated water to determine post treatment contamination. In systems involving pollution from land areas and runoff, many coliform sp. of natural origin (non-enteric) can be introduced so as to make this organism ineffective as a true sign of fecal contamination. Fecal coliforms eliminate this problem because they are only produced in the intestines of warm blooded animals. Fecal streptococci are less specific in nature but are also predominately isolated only from enteric sources (Geldreich, 1976). Problems in identification and specificity of testing methods for elimination of non-enteric fecal streptococci sp. is native to vegetation, soil and insects have been reported (Kibbey et al., 1978; Hunt et al., 1979; Geldreich, 1976). The best choice of indicator for any particular study depends on the sample source, environmental conditions and geographic location as well as the use to be made of