Environmental Risk Factors in the Human Pathogen Transmission Pathways between Animal Operations and Produce Crops

Once zoonotic pathogens leave their animal hosts, how they move through the environment and are deposited on unharvested produce remains a persistent industry challenge and research question related to produce safety. The proximity of animals to production areas, animal types and densities, an animal operation’s management practices, and weather conditions are some of the areas explored by researchers to better understand how pathogens contaminate unharvested crops. Water, inputs, airborne particulates, wildlife, and insects may serve as vectors linking pathogens from their animal hosts to produce production areas. Studies have shown a positive correlation between rainfall and pathogen concentrations in agricultural water downstream from animal operations. Bacteria attached to airborne particulates can be deposited onto crops or open water sources. Wildlife and insects share habitat with domesticated animals in rangelands, pasture settings, pens, and feedlots. Plant conditions (injuries, disease) and characteristics (surface topography, genetic traits, age, native microbiota) and environmental conditions (relative humidity, moisture, temperature) play a major role in determining pathogen survival on unharvested produce. This article explores recent research findings elucidating human pathogen dispersion and deposition, subsequent transfer from animals to crops, and the various environmental risk factors along the way that play a role.