Summary of Awards to Date

Sources and mechanisms of transfer of Salmonella in the production and postharvest tree nut environment.

Date

Jan. 1, 2012 - Feb. 28, 2014

Award Number

2012-201

Amount Awarded

$317,320.00

Investigator

Linda J. Harris, Ph.D.
University of California, Davis

Co-Investigator(s)

Michele Jay-Russell, Ph.D.

Resources
Summary

Over the past decade, contamination of nuts with Salmonella has led to numerous recalls and two outbreaks in the U.S. However, sources of Salmonella in nut production and processing are not well understood. We hypothesize that contamination of almonds and pistachios with Salmonella is facilitated by movement of dusts in orchards and during initial post-harvest handling. We also speculate that airborne dust from animal feeding operations (dairies, feedlots) in close proximity to orchards may play a role in the spread of this pathogen. To test this hypothesis we will work closely with our collaborators in the almond, pistachio, and livestock industries to identify collaborating farms, hulling/shelling (almonds), and hulling/processing (pistachio) facilities. Environmental sampling and microbiological analyses will be used to characterize the microbial composition of bioaerosols and dust originating from livestock operations located in close proximity to almond and pistachio production areas in the California central valley; evaluate movement of microorganisms from livestock operations to nearby almond and pistachio orchards; and evaluate the microbial composition of bioaerosols and dusts at almond hullers/shellers and pistachio hulling facilities. Knowledge gained from this study will be shared with stakeholders to improve good agriculture practices that protect almond and pistachios from Salmonella contamination.  

 Technical Abstract

Foodborne disease outbreaks and recalls have been linked to consumption of contaminated raw and in-shell nuts (almonds, hazelnuts). In 2009 and 2010, type I recalls due to Salmonella contamination occurred in pecans, pistachios, macadamia nuts, hazelnuts, pine nuts and walnuts. The primary vectors and transport pathways leading to contamination by Salmonella remain unclear, but potential sources include livestock, local wildlife, and possible niches of self-sustaining Salmonella shown previously to replicate on the orchard floor under certain environmental conditions.  We hypothesize that contamination of the almonds and pistachios by Salmonella occurs primarily through movement of bioaerosols and airborne dusts generated from concentrated animal feeding operations (dairies, feedlots) in close proximity to the orchards.  To test this hypothesis we will work closely with our collaborators in the almond, pistachio, and livestock industries to identify collaborating farms, hulling/shelling (almonds), and hulling/processing (pistachio) facilities.  The long-term goal of the project is to develop and implement science-based strategies to prevent off-orchard dissemination of Salmonella from livestock sources to almond and pistachio crops.  We will accomplish our goal by completing the following objectives: 

Objective 1a.  Characterize the microbial composition of bioaerosols and dust originating from livestock operations located in close proximity to almond and pistachio production areas in the California central valley.  Objective 1b.  Evaluate the movement of microorganisms from livestock operations to nearby almond and pistachio orchards compared with control orchards not in proximity to livestock operations.  And Objective 2:  Evaluate microbial composition of bioaerosols and dusts at a) almond hullers/shellers and b) pistachio hulling facilities