Potential risk factors for Brachyspira hyodysenteriae, Lawsonia intracellularis and Salmonella spp. infection and their prevalence in commercial swine farms in Thailand

The aims of the present study were to evaluate the prevalence for Brachyspira hyodysenteriae, Lawsonia intracellularis and Salmonella spp. in pig feces and to identify their risk factors in 20 commercial swine farms in Thailand. The crosssectional study was carried out from 20 farrow-to-finishing commercial swine farms in part of Thailand including the north (n=5), northeast (n=4), east (n=5), west (n=4) and south (n=1). A total of 589 fecal samples were randomly collected from 12 (n=200), 16 (n=196) and 20 (n=193) aged a week-old in each farm. All samples were analyzed for the detection of B. hyodysenteriae, L. intracellularis and Salmonella spp., in feces by multiplex PCR. The prevalence for B. hyodysenteriae, L. intracellularis and Salmonella spp., in positive farms was 45.0% 85.0% and 10.0%, respectively (P>0.05). The prevalence in open housing system for B. hyodysenteriae and L. intracellularis (62.5%) had a tendency to be higher than a closed housing system (62.9% VS 33.3%, P=0.199 and 100.0% VS 75.0%, P=0.125, respectively). No effect of farm size, location of farm, number of sites and the diarrhea status on the prevalence for all pathogens was found. The pigs aged at 12 weeks (15.0%) had the prevalence for B. hyodysenteriae positive samples higher than the pigs aged at 16 weeks (3.3%, P=0.027) but did not differ significantly compared to the pigs aged at 20 weeks (6.7%, P=0.142). In conclusion, L. intracellularis is the main cause of intestinal bacterial infection in growing-finishing pigs in Thailand, especially in open housing system farms.