Epidemiology of foodborne pathogens in wild rodents in a major agricultural region of the California central coast

Recent outbreaks of foodborne illness associated with consumption of raw agricultural produce products has increased concern over wildlife reservoirs of foodborne pathogens. Evidence of internalization and proliferation of foodborne pathogens in agricultural produce tissue parts highlights the importance of enhancing pre-harvest food safety. A 2006 E. coli O157:H7 outbreak in the Salinas valley region, California, linking contaminated spinach to nearby feral swine, prompted the initiation of stringent wildlife control measures aimed at reducing wildlife access to produce production blocks. Fencing, poison baiting and clearing of non-crop vegetation in areas adjacent to produce fields are some methods employed by farmers in the agriculturally rich region. Such methods are capable of targeting many rodent species despite the lack of sound scientific evidence linking many of them to crop contamination.;Riparian areas, chaparral, annual grassland and rangeland are all characteristic flora adjoining cropland in the region and form the essential habitat for numerous species of wild rodents. This close proximity between fields of produce and wildlife habitat can provide ample opportunity for produce contamination should infected rodents gain access, nest, forage and/or defecate within or alongside fields of produce, or contaminate irrigation water supplies and related equipment.;The role of various small mammal species as potential reservoirs of deleterious pathogens such as Salmonella and E. coli O157:H7, however, still remains uncertain. Prior studies have focussed on commensal species on animal agricultural operations and the potential for pathogen inter-species transmission between domestic and wild animals. Wild rodents are ubiquitous and thrive wherever food stocks and habitats are plentiful; thus many species can live in close proximity to humans and livestock. These wildlife species are competent reservoirs of a number of zoonotic diseases responsible for significant economic losses and public health problems. Despite this, there have been few studies that assess the role of wild rodents in shedding food-borne pathogens, particularly those inhabiting produce production areas. This project addresses these pertinent issues and provides an insight into the role of wild rodents as potential reservoirs and vectors of food-borne pathogens in produce production farms, cow calf operations and a beef feedlot in central coastal California.;A literature review in Chapter 1 assessed what is known about wild rodents as sources of foodborne pathogens and crop damage in agricultural farms. Presented in Chapter 2 are the findings of a longitudinal study investigating the risk factors associated with fecal shedding of foodborne pathogens by wild rodents. Chapter 3 provides quantitative estimates of protozoan shedding by wild deer mice in agricultural farms as well as rodent intrinsic factors (age and sex) associated with increased environmental loading of protozoa. Chapter 4 comprises a capture mark recapture study aimed at estimating rodent densities in farms in California and investigates agricultural landscape features associated with increased odds of rodent capture.