Microbiota of vaccinated and non-vaccinated clinically inconspicuous and conspicuous piglets under natural Lawsonia intracellularis infection

Lawsonia (L.) intracellularis is an economically important bacterium causing the porcine proliferative enteropathy (PPE) and is widespread in European countries. Oral vaccination with an attenuated L. intracellularis strain is approved to reduce intestinal lesions due to L. intracellularis infection, growth variability and loss of weight associated with the disease. However, neither infection nor transmission of the bacterium are prevented by vaccination. Strong associations of L. intracellularis with other bacteria present in the swine gut were shown in pigs experimentally challenged with L. intracellularis. However, studies that investigate microbiome changes induced by L. intracellularis in natural field conditions are still missing. To the best of our knowledge, the present study is the first study that examined standardized the intestinal microbiota of pigs non-experimentally challenged but naturally exposed to L. intracellularis. By comparing vaccinated and non-vaccinated clinically inconspicuous piglets, we could show differences in microbiota composition of pigs related to oral L. intracellularis vaccination. Furthermore, differences in the microbiota composition according to the outcome of the disease were also observed, as shown by the comparison between non-vaccinated clinically inconspicuous and conspicuous piglets. Results from the present study contribute to a better understanding of the establishment and severity of the disease.