Synergic Effect of Brachyspira hyodysenteriae and Lawsonia intracellularis Coinfection: Anatomopathological and Microbiome Evaluation

SIMPLE SUMMARY: Clinical and anatomopathological evaluations of animals experimentally inoculated with Brachyspira hyodysenteriae and 7 days later with Lawsonia intracellularis were performed and compared to single-infected pigs. Co-infected animals were more affected and had more severe lesions when compared to single-infected pigs. The intestinal microbiome of pigs from co-infected animals demonstrated a difference in some genera compared to other groups before and after inoculation and certain genera were evaluated in each group. ABSTRACT: Brachyspira hyodysenteriae and Lawsonia intracellularis coinfection has been observed in the diagnostic routine; however, no studies have evaluated their interaction. This study aimed to characterize lesions and possible synergisms in experimentally infected pigs. Four groups of piglets, coinfection (CO), B. hyodysenteriae (BRA), L. intracellularis (LAW), and negative control (NEG), were used. Clinical signals were evaluated, and fecal samples were collected for qPCR. At 21 days post infection (dpi), all animals were euthanized. Gross lesions, bacterial isolation, histopathology, immunohistochemistry, and fecal microbiome analyses were performed. Diarrhea started at 12 dpi, affecting 11/12 pigs in the CO group and 5/11 pigs in the BRA group. Histopathological lesions were significantly more severe in the CO than the other groups. B. hyodysenteriae was isolated from 11/12 pigs in CO and 5/11 BRA groups. Pigs started shedding L. intracellularis at 3 dpi, and all inoculated pigs tested positive on day 21. A total of 10/12 CO and 7/11 BRA animals tested positive for B. hyodysenteriae by qPCR. A relatively low abundance of microbiota was observed in the CO group. Clinical signs and macroscopic and microscopic lesions were significantly more severe in the CO group compared to the other groups. The presence of L. intracellularis in the CO group increased the severity of swine dysentery.