Prevalence of Lawsonia intracellularis and characteristics of gut microbiomes of the infected pigs in Shaanxi province, China

Objectives Lawsonia intracellularis is an obligately intracellular enteric bacterium that infects intestinal epithelial cells and causes porcine proliferative enteropathy (PPE). This study aimed to investigate the epidemiological prevalence of L. intracellularis in large-scale pig farms in Shaanxi Province, China, and analyze the differences in fecal microbial communities of growing pigs with natural L. intracellularis infection. Methods A total of 672 fecal samples and 300 serum samples were collected from five intensive pig farms in Shaanxi during 2022–2023. Quantitative PCR (qPCR) was used to detect L. intracellularis in feces and quantify its fecal load, while enzyme-linked immunosorbent assay (ELISA) was employed to detect the seroprevalence of anti- L. intracellularis antibodies in serum. 16S rRNA gene sequencing was performed on fecal samples from L. intracellularis -positive and -negative growing pigs. Results The results showed an overall fecal positive rate of 15.3% (95% CI: 12.7–18.3%) and a serum seroprevalence of 14.7% (95% CI: 11.0–19.3%) for L. intracellularis in the surveyed farms, with growing pigs exhibiting the significantly highest positive rate and fecal pathogen load ( p < 0.05). Tongchuan exhibited a significantly lower fecal positive rate than the other surveyed regions ( p < 0.05). Fecal microbial diversity analysis revealed that L. intracellularis -positive fecal samples exhibited significantly higher bacterial species richness. LEfSe analysis indicated a significant enrichment of Lactobacillus in L. intracellularis -positive feces relative to negative samples. Network analysis demonstrated a positive correlation between Desulfovibrionaceae and Lachnospiraceae , and random forest analysis identified Erysipelotrichaceae_UCG.003 as the critical microbial biomarker for L. intracellularis infection. Conclusion This study elucidates the epidemiological characteristics of L. intracellularis in Shaanxi and its interaction with the porcine gut microbiome, thereby providing a theoretical basis for the precise prevention and control of PPE, as well as for further investigations into the interactions between the gut microbiota and L. intracellularis .