First evidence of Lawsonia intracellularis detection in air from commercial swine farms

Abstract

Lawsonia intracellularis is the etiological agent of porcine proliferative enteropathy (PPE), a major enteric disease present in most swine herds worldwide. PPE expression is influenced by several factors, making continuous surveillance essential to minimize its impact. This study evaluated the feasibility and diagnostic performance of environmental sampling for the detection of L. intracellularis in commercial swine farms with subclinical and PPE infections. Three farms (A–C) were included: Farms A and B exhibited subclinical infection, while Farm C was affected by a PPE outbreak. Longitudinal sampling included serum, fecal swabs, air and surface samples from 10 to 11 to 17–18 weeks of age. Serology and quantitative PCR (qPCR) were used to monitor infection and quantify L. intracellularis loads. L. intracellularis infection was confirmed in all three farms using standard diagnostic methods. DNA of L. intracellularis was consistently detected in air and surface samples, with distinct temporal patterns across farms. In subclinical infected herds, early low-level detection in air and surface samples preceded widespread shedding, which was subsequently reflected in increased seroprevalence. In the PPE affected farm, high seropositivity and fecal shedding were observed during the outbreak, followed by a gradual decline. These dynamics were also mirrored by the quantity of L. intracellularis DNA detected both in air and surfaces over time. These findings demonstrate that environmental monitoring via air and surface sampling is might be a possible tool in the future to predict infection dynamic under both subclinical and clinical PPE conditions, providing a complementary method for the early detection and surveillance of L. intracellularis