Swine production intensity and swine-specific fecal contamination of household surfaces at residences of industrial livestock operation workers and community residents, North Carolina, USA

In North Carolina (NC), industrial livestock operations (ILOs) that produce swine concentrate fecal waste in lagoons and sprayfields, which are disproportionately located in low-income communities of color. Although swine-specific fecal contamination of surface waters proximal to swine ILOs has been documented, less is known about contamination of homes proximal to swine ILOs. Up to 6 outdoor and 6 indoor surface settled dust samples were collected from households: 1) with >= 1 ILO worker (ILO-W); 2) neighboring ILOs without occupational exposure to livestock (ILO-N); and 3) in metropolitan areas of NC (Metro). Using quantitative real-time PCR, the DNA copy number of Pig-2-Bac, a swine-specific fecal microbial source tracking (MST) marker, per square inch of household surfaces sampled was measured. We used permits of swine ILOs and steady state live weight to assign swine production intensity (SPI) exposure values to each household. We estimated associations between household group (Metro as reference), outdoor versus indoor household surface, and log10 SPI with Pig-2-Bac DNA detection frequency (logistic) and quantity (linear) via regression modeling. Prevalence of household Pig-2-Bac positivity was 38 % (40/105) at ILO-W (159/536 swabs; 30 %); 44 % (47/107) at ILO-N (142/557 swabs; 25 %), and 1 % (1/81) at Metro (1/321 swabs; 1 %) households. Pig-2-Bac DNA was detected more often (odds ratio [OR] = 2.2; 95 % confidence interval [CI] = 1.6, 3.0) and in higher quantity (β = 0.30; 95 % CI = 0.19, 0.41) on outdoor compared to indoor surfaces. For every log10 unit increase in SPI, the Pig-2-Bac DNA detection frequency (OR = 5.4; 95 % CI = 2.8, 10.4) and quantity (β = 0.21; 95 % CI = 0.13, 0.29) increased. Results demonstrate the utility of Pig-2-Bac DNA measurement in household surface dust and suggest that swine ILOs contribute to the contamination of NC community residents' households with swine fecal material.