Bordetella bronchiseptica experimental model development in pigs and efficacy evaluation of a single intramuscular injection of gamithromycin (Zactran® for Swine) against Bordetella bronchiseptica-associated respiratory disease in experimentally infected piglets

In the Bordetella bronchiseptica infection model development study, twenty-eight piglets were inoculated with B. bronchiseptica strain of either canine (10⁹ CFU/ml) or swine (10⁸ and 10⁹ CFU/ml) origin; swine origin strain at 10⁹ CFU/ml was chosen for the efficacy assessment study due to higher incidence and severity of gross and histopathological lesions compared with other strains. To assess efficacy of gamithromycin against B. bronchiseptica, forty piglets were experimentally inoculated on Day 0 and clinical signs were scored as per severity. Animals were then treated either with gamithromycin or saline on Day 3. The Global Clinical Scores in gamithromycin-treated group were consistently lower than the saline-treated control group from Day 4 onwards and were 0 and 40 in the gamithromycin-treated and saline-treated control groups, respectively, on Day 6. Severity and frequency of gross and histopathological observations were significantly lower in gamithromycin-treated animals compared with saline-treated controls. The efficacy of Zactran® for Swine at the label dose for the treatment of B. bronchiseptica–associated respiratory disease was demonstrated based on the faster reduction in clinical signs as early as 1 day post-gamithromycin treatment and based on the significant difference in the severity of macroscopic and microscopic lung lesions 10 days post-gamithromycin treatment.