The occurrence of Bordetella bronchiseptica in pigs with clinical respiratory disease.

Between January 2003 and September 2008, 652 Bordetella bronchiseptica isolates were cultured from 3506 lung samples collected from pigs with respiratory disease. Over the 6-year period, the average isolation rate was 18.6%, making B. bronchiseptica the fourth most frequently isolated pathogenic bacterium from those lung samples. The isolation rates in different years and provinces ranged from 15.2% to 25.7% and 17.3% to 20.7%, respectively. There were significant influences of sampling month and pig age on bacterial isolation (P<0.05). Streptococcus suis (29.9%), Haemophilus parasuis (26.7%) and Escherichia coli (21.6%) were isolated most frequently in association with B. bronchiseptica. All 12 toxigenic Pasteurella multocida strains co-isolated with B. bronchiseptica from 63 cases of atrophic rhinitis were classified into serogroup D. The results suggest that B. bronchiseptica infection is highly prevalent in pig farms in China, and is often accompanied by co-infection with other bacteria.