Oral vaccination against Lawsonia intracellularis changes the intestinal microbiome in weaned piglets

"Lawsonia intracellularis, which causes porcine proliferative enteropathy (PPE), is a common swine intestinal pathogen that is prevalent in pig production sites worldwide. In this study, alteration in the microbiome composition of weaned pigs were investigated in response to vaccination against L. intracellularis using 16S rRNA gene sequencing. A total of 64 crossbred (Duroc x [Landrace x Yorkshire]) healthy weanling pigs weaned at 4 weeks of age were randomly assigned to 4 treatment groups (4 pigs/pen; 4 pens/treatment) using a randomized complete block design for the 42 days trial. Pigs in the treatment groups were orally administered with three different doses (1 dose = 2mL) of vaccine against L. intracellularis (Enterisol Ileitis, Boehringer Ingelheim Vetmedica GmbH) namely: LAW1 (0.5 dose), LAW2 (1 dose), LAW3 (2 dose). A non-challenged group served as a negative control (CONT). Alpha diversity analysis revealed that vaccination led to significant changes in species evenness and not species richness of the gut microbiota. Beta diversity analysis revealed that vaccination against L. intracellularis caused a significant shift in the microbial community structure. In addition, oral vaccination against L. intracellularis significantly enriched the population of Streptococcus and caused significant depletion of Clostridium species, which may provide benefits and growth of potential pathogens in piglets. This study highlights areas where the pig gut microbiome holds specific promise in vaccinology."