Oral fluid for detection of exposure to Lawsonia intracellularis in naturally infected pigs

•There was simultaneous detection of IgG against Lawsonia intracellularis in serum and oral fluid (OF).•OF can be used to detect antibodies against Lawsonia intracellularis in older (finisher and pre-slaughter) pigs.•OF might determining the L. intracellularis kinetics of infection in a herd. To demonstrate the utility of oral fluid (OF) for indirect diagnostic detection of Lawsonia intracellularis (Li), 15 pig farms were studied. Serum and fecal samples were collected from 20 animals from five different age groups on each farm. OF samples were collected from animals in two pens of the same age groups. Serum and OF samples were analyzed in an immunoperoxidase in monolayer assay (IPMA) for the detection of anti-Li immunoglobulin G (IgG) and A (IgA). Compatible results were found between PCR and IgG in OF in four of the five ages evaluated. Simultaneous detection of IgG in serum and OF was mainly observed on farms showing clinical signs suggestive of porcine proliferative enteropathy (PPE). These findings demonstrate the potential usefulness of OF in detecting anti-Li antibodies as a diagnostic tool that can be used to monitor PPE in herds with clinical signs compatible with the disease.