A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs

Background: The major pathogenic intestinal spirochetes affecting pigs during the growing- finishing stage of production include Brachyspira hyodysenteriae and Brachyspira pilosicoli. The aim of this study was to assess the current occurrence of B. hyodysenteriae and B. pilosicoli in Polish pig herds. Moreover, associations between the presence of diarrhea or other intestinal pathogens and occurrence of B. hyodysenteriae and B. pilosicoli in pigs were investigated. Methods: Between January 2017 and August 2019, a total of 401 samples of pig feces from 95 different herds were submitted to the National Veterinary Research Institute of Poland. These samples were obtained from pigs older than 7 weeks. All the received fecal samples were examined for the presence of B. hyodysenteriae, B. pilosicoli and Lawsonia intracellularis by real-time PCR. Results: B. pilosicoli was detected in 4.5% (95% CI, 2.5–7.0%) (18/401) of pig fecal samples. At the herd level 13.7% (95% CI, 7.5–22.3%) (13/95) of herds were positive for B. pilosicoli. B. hyodysenteriae was detected in 7.0% (95% CI, 4.7–9.9%) (28/401) of pig fecal samples and 18.9% (95% CI, 11.6–28.3%) (18/95) of pig herds were positive. Out of 18 B. pilosicoli positive samples, this pathogen was detected alone in 5 samples; simultaneously with L. intracellularis in 9 samples; simultaneously with B. hyodysenteriae in 1 sample and in 3 samples was detected simultaneously with both of these bacteria. The presence of B. hyodysenteriae in fecal samples was associated with the presence of diarrhea in pigs. Conclusions: This study confirmed that B. pilosicoli infections occur in Polish pig herds, but the prevalence is at a low level and the presence of B. pilosicoli is not associated with the development of diarrhea in pigs. B. hyodysenteriae is still a common cause of diarrhea among pigs from Polish herds.