Survival and Transport of E. Coli O157:H7 and Salmonella Newport in Manure and Manured Soils

Non-Technical Summary: Escherichia coli O157:H7 (E. coli O157) and Salmonella enterica serovar Newport (Salmonella Newport) are zoonotic pathogens imposing serious public health concerns. The E. coli O157 outbreak in the fall of 2006 via contaminated spinach is a recent example, whereas Salmonella Newport currently ranks third by CDC in causing human intestinal infections. Both pathogens have established reservoirs in dairy cattle. As infected animals shed the organisms in manure and manure is subsequently spread on agricultural land, the pathogens may be transmitted to plants, other animals or humans, or transported into waters. However, information is lacking on how the organisms may survive and move in the post-shed environment. The purpose of this project is to enhance the understanding of the fate and impact of these pathogens in agroecosystems and to contribute to the development of science-based and farm-applicable management strategies for their controls. Specific objectives are: (i) Assess the survival characteristics of E. coli O157 and Salmonella Newport in manure and manured soils under laboratory conditions, (ii) Determine the persistence of the organisms in different manure handling/storage and cropping systems on farms, (iii) Investigate the transport behavior and factors affecting movement of the organisms from manured soils to waters through leaching studies and on-farm investigations. The project is readily executable and is supported by a multi-disciplinary team with well-tested protocols. <P> Approach: To accomplish project objectives, we have formulated scientific hypotheses and designed a series of experiments to test these hypotheses. Hypothesis one: The survival pattern of E. coli O157 or Salmonella Newport can be altered by manipulating manure pH or temperature, and soil type and moisture levels have significant impacts on the persistence of the organisms when applied with manure to soils. Laboratory trials will be conducted to study the persistence of the pathogens in manure alone or in manure-soil mixtures under different pH, temperature, soil type and moisture conditions. Repeated sampling and testing across time will be performed to establish the survival kinetics of the organisms. Hypothesis two: The survival pattern and die-off time of the organisms differs according to the type of manure handling facility as well as soil-crop systems. This hypothesis will be tested on farms of actual manure handling/storage facility and crop fields using sentinel chambers which allow the containment of the organism and prevent them from contaminating the test sites. The sentinel chambers containing E. coli O157 or Salmonella Newport spiked manure samples will be embedded in the manure storage or the crop fields and periodic sampling and testing will be performed. Hypothesis three: E. coli O157 or Salmonella Newport inoculated into manure and applied to soils can be transported through leaching processes; the transport differs in different soils and decreases with increase in time between manure application and rainfall events. The hypotheses will be tested through leaching studies using soil cores exposed to varying simulated rainfall patterns and different soils (clay loam, sandy loam, and silt loam) amended with dairy feces inoculated with the target organisms. Simulated rainfalls will represent different precipitation patterns. In addition, field investigations will monitor presence of the organisms on selected dairy farms with schematic sampling and testing of feces, stored manure, field soil, crops and surface waters.