Source tracking and transmission risk of Campylobacter spp on mixed produce crop-livestock farms using rotational grazing

Mixed crop-livestock farms (i.e. bio-diversified farms) are farms where animals and crops are raised with the goal of utilizing the products of one for the growth of the other. Mixed produce growers in northern California have divLogosersified their production system to include a rotation of livestock in order to manage plant biomass, add manure to the soil, and increase products produced on the farm. For produce farms, re-integrating animals back into cropland provides benefits in profitability and environmental sustainability such as, reducing pests/weeds, improving of soil fertility, strengthening of farm economies, and increasing regional food security. However, these systems face challenges, including potential food safety risks and compliance with third=[arty audit criteria and newly proposed regulations in produce production. For example, auditors and regulators may discourage or prohibit raising livestock alongside vegetable crops as done in rotational grazing for crops (e.g., leafy greens, melons) known to be vulnerable to microbial contamination by fecal-born zoonotic pathogens. Specifically, raw manure from grazing animals may introduce foodborne pathogens such as Campylobacter, Salmonella, Shiga toxin-producing Escherichia coli (STEC) into fields, and these pathogens can persist in the soil for extended periods of time. Campylobacter species are commonly isolated from pasture raised livestock (ruminants and swine) and poultry. Persistence of Campylobacter spp. In bovine manure has been documented during the composting process and fresh produce has been documented as a vehicle for campylobacteriosis illnesses. Campylobacter spp have also been found in vegetable sold at Farmer’s markets, a common venue for bio-diverse farm products. In addition, the risk of Campylobacter amplification and dissemination may be increased in systems with multi-species grazing that could promote cross-species transmission. The Current National Organic Program (NOP) requires that untreated animal manure be applied at least 120 days or 90 days prior to the harvest of crops, depending on whether the edible portions come into direct or indirect contact with the treated soil. However, there is limited data defining the microbial risk or adequate waiting period after animals are grazed on a produce field. Organic farmers are currently discouraged by some third-party auditors and the Leafy Green Marketing Agreement (LGMA) from grazing animals in produce fields during the fallow period, or they must implement a strict 12-month waiting period that is not compatible with most cropping cycles in California and other regbions. Recent outbreaks and raw milk recalls due to Campylobacter contamination traced to pasture-based dairy farms in California, in addition to the high prevalence of Campylobacter in organic/pastured raised poultry carcasses and pasture farm environments, highlights the need to investigate transmission dynamics in rotational grazing systems involving multi-species. Moreover little scientific data exists regarding the risk of inter-species transmission and resulting risk to microbial contamination of fresh produce crops. The goal of this study is to investigate the prevalence of Campylobacter spp, on farms integrating livestock and produce production by rotational grazing, and source track potential movement of strains between species (cattle-poultry; swine-poultry and small ruminants-poultry).