Reducing the risk for transfer of zoonotic foodborne pathogens from domestic and wild animal to vegetable crops in the southwest desert

Reducing the risk for transfer of zoonotic foodborne pathogens from domestic and wild animal to vegetable crops in the southwest desert

Jan. 1, 2013 - Dec. 31, 2014

2013-286

$252,777.00

Michele Jay-Russell, Ph.D.
University of California, Davis

Anne Justice-Allen

Final Report

We propose to conduct a study that will help the leafy greens produce industry identify domestic and wildlife animal reservoirs of shiga toxin-producing E. coli (STEC) and Salmonella in the desert southwest growing region (DSGR) of the U.S. and northern Mexico, a region second only to the central California coast in production of lettuce. Additionally, we will identify management and risk mitigation practices that reduce contamination of leafy greens by these species. Scientific collections and epidemiologic methods will be used to complete three main objectives: 1) determine if terrestrial and avian wildlife species reported by the local growing community to most frequently intrude upon produce fields in the DSGR, are reservoirs of STEC and Salmonella; 2) determine the extent to which wildlife and livestock share genetically related strains of STEC and Salmonella, and measure the movement of strains from livestock operations to produce fields by wildlife populations; 3) extend knowledge of produce contamination prevention gained from the first two objectives to growers.  Data from this collaborative study between industry, game management, and academic organizations will fill gaps in knowledge pertaining to animal intrusions and establishing buffer zones between adjacent livestock and produce operations in the desert environment.

Technical Abstract

Foodborne disease illnesses caused by pathogenic bacterial contamination of fresh produce are being recognized in greater numbers in the United States (Sivapalasingam et al, 2004; Lynch et al, 2009). The role of domestic and wildlife animals as reservoirs and transmitters of bacterial pathogens to fresh produce has been studied at length in some growing regions, such as the California central coast (Cooley et al, 2007; Jay et al, 2007; Gorski et al, 2011). In contrast, limited information exists on the importance of animal sources of contamination in the desert southwest growing region (DSGR), a major fresh vegetable production region of the US-Mexico border that is second only to central California in terms of lettuce production. These knowledge deficits may lead to uninformed environmental assessments and management decisions, especially those pertaining to mitigation efforts following animal intrusion and implementation of appropriate buffer zones between neighboring livestock and produce lands.

The long-term goal of this project is to identify potential domestic and wild animal reservoirs of foodborne pathogens in leafy green production regions of the DSGR, and to use this knowledge to guide industry practices while minimizing impacts on wildlife species and their habitat. During the 2010-2011 DSGR season, our research team conducted the first phase of this study by examining local canid (dog, coyote) reservoirs in collaboration with leafy greens industry partners (Jay-Russell, 2011). This proposal represents the next phase of the research and will complete the following objectives: 

Objective 1: To determine if domestic animals and terrestrial and avian wildlife species in the desert southwest produce production region are reservoirs of shiga toxin-producing E. coli (STEC) or Salmonella. We will utilize livestock surveys, and hunter-harvested and targeted sampling and testing of feces and colon from terrestrial and avian wildlife species to assess the potential pathogen burden of these animals.

Objective 2: To determine the extent to which wildlife and cattle share genetically related strains of STEC and Salmonella, and measure the movement of strains from livestock operations to produce fields by wildlife populations. We will utilize intensive trapping and radio telemetry with spatial analysis to assess animal movements and the potential spread of pathogens including evaluation of the interim Leafy Green Marketing Agreement guidance distance of 400 ft from a concentrated animal feeding operation to the edge of a crop. Molecular genotyping will provide a comparison of the genetic relatedness of strains isolated from these animals with strains from nearby livestock.

Objective 3: Extend knowledge of preventing produce contamination by domestic animals and terrestrial and avian wildlife populations to the produce and livestock communities. We will share the knowledge gained from this study with growers, ranchers, buyers, regulators, conservation groups, and other stakeholders to improve best practices relating to pre-season and pre-harvest environmental assessments and wildlife intrusion, and no-harvest buffer zones. 

These objectives will be met by utilizing partnerships with local industry collaborators and the Arizona Game and Fish Department’s Research Branch. Hypotheses will be tested through bacteriologic and molecular microbiologic approaches, and spatial and statistical epidemiologic analysis. Results from this study will improve environmental assessments and intervention management decisions in support of both food safety and environmental stewardship.