Occurence and survival of zoonotic bacterial pathogens and indicator organisms in groundwater and sandy soil following field application of hog manure

With growing concerns regarding the human and animal safety of manure application to agricultural fields, it is imperative that work be done to address and investigate the microbiological safety of this practice. Several organisms of concern, such as Salmonella, Escherichia coli and Yersinia are capable of survival in manure, soil and water environments. The objectives of the research were to examine coliform and Pseudomonas levels in well water from the experimental site following the application of manure, to examine survivability of pathogenic organisms in the well water and to determine if Salmonella could travel through soil columns taken from the study field. Results obtained indicated that only 2.3% of 603 water samples over 20 months contained confirmed positive coliforms, with only 2 instances of fecal coliform detection (one positive sample in the unmanured section of the field). The presence of coliforms appeared to be unrelated to the application of manure during these experiments. However, many of the well water sampling times were >100 d after manure application. The survival of pathogenic organisms in well water at 5°C revealed that Yersinia persisted throughout the 91d testing period in the highest numbers, while Salmonella survived the least well, between 21 to 56 d. E. coli was detectable until the end of 91d, but in lower numbers than Yersinia. From the soil column perfusion experiments, Salmonella were detected in the effluent from 4/6 columns, however in low numbers (0.01-0.11% of the added inoculum). Recovery of Salmonella in soil from dissected columns revealed the highest concentrations of the organism in the top 20 cm of the column. From these results, it was determined that the sandy soil was capable of filtering large quantities of Salmonella from inoculated water, which may aid in the prevention of contamination of groundwater following the application of manure to agricultural fields.