The fate of Salmonella and Escherichia coli O157:H7 in swine or dairy manure amended into sandy loam or loam soil under field conditions was studied. Soil was amended with manure inoculated with a Salmonella or E. coli O157:H7 cocktail, then transferred to 0.22 μm pore size membrane walled vials. The vials were then placed on the surface or at 15 cm depth in the test plots. Pathogen numbers, soil moisture, rainfall, and temperature were measured throughout the three trials (20–47 weeks duration) representing spring or fall application. Survival curves were characterized by having an initial rapid decline in pathogen numbers followed by a slower inactivation phase with an occasional increase in culturable cells. The CT99.9 values (time to reach a 3 log CFU reduction) varied from 2 to 120 days, with the most rapid decrease being observed on the surface of sandy loam soil. The persistence of pathogens is primarily governed by variations in moisture and temperature, although season of application along with manure and soil type also contribute. To generate more accurate predictive pathogen models, there is a need for laboratory-based trials to mirror the dynamic variation in temperature and soil moisture encountered within the natural environment.
This comes as we investigate a rise in cases of a particular strain of Salmonella Typhimurium which have been linked to lamb and mutton. We first saw an increase in cases of this particular type of salmonella in July 2017. A number of control measures were put into place which led to a significant decline in cases at the end of that year. A total of 118 cases were reported up until May 2018.
Since June 2018, a further 165 cases have been reported (up to 19 October), which led us to put control measures in place. This hasn’t led to the same decline in cases as in 2017 and so we are now reminding the public about how to cook and handle raw meat.
Colin Sullivan, Chief Operating Officer at the Food Standards Agency said: ‘We are advising care when preparing all meat, including lamb and mutton, to reduce the likelihood of becoming ill with Salmonella Typhimurium. Our advice is to purchase food as normal but to take care when storing, handling and cooking raw meat.
‘People should wash their hands after touching raw meat, avoid contaminating other food in the kitchen by storing it separately in the fridge and using different chopping boards and knives, and ensure that meat, particularly diced and minced lamb, is cooked properly.’
Nick Phin, Deputy Director, National Infection Service, PHE said: ‘The likely cause of the increased numbers of this specific strain of Salmonella Typhimurium is considered to be meat or cross-contamination with meat from affected sheep. People can be infected with Salmonella Typhimurium in a number of ways such as not cooking their meat properly, not washing hands thoroughly after handling raw meat, or through cross-contamination with other food, surfaces and utensils in the kitchen.’