A new single-dose bivalent vaccine of porcine circovirus type 2 and Mycoplasma hyopneumoniae elicits protective immunity and improves growth performance under field conditions

• The bivalent vaccine elicited immune responses against PCV2 and M. hyopneumoniae.
• Pigs vaccinated with the bivalent vaccine decreased mortality rate of 13.4%.
• Pigs vaccinated with the bivalent vaccine increased market weight of 6.2 kg/pig.

The efficacy of the new single-dose bivalent vaccine of porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae was evaluated under field conditions for registration as recommended by the Republic of Korea’s Animal, Plant & Fisheries Quarantine & Inspection Agency. Three farms were selected based on their history of co-infection with PCV2 and M. hyopneumoniae. On each farm, a total of 80 3-week-old pigs were randomly allocated to one of two treatment groups: (i) vaccinated (n = 40) and (ii) unvaccinated (n = 40) animals at 3 weeks of age. Protection by the bivalent vaccine helped increase the market weight by 6.2 kg/pig (106.2 kg in vaccinated group vs. 100 kg in unvaccinated group; P < 0.05) and decreased mortality rate by 13.4% (0.8% in unvaccinated group vs. 14.2% in unvaccinated group; P < 0.05). Vaccinated animals induced PCV2-specific neutralizing antibodies (NA) and interferon-γ secreting cells (IFN-γ-SC), and M. hyopneumoniae-specific IFN-γ-SC. Vaccinated animals displayed a reduced PCV2 load in the blood and M. hyopneumoniae load in nasal swabs compared to unvaccinated animals. Vaccination of pigs against PCV2 and M. hyopneumoniae effectively reduced the lung and lymphoid lesion scores compared to unvaccinated animals in all 3 farms. The new bivalent vaccine is very efficacious in controlling PCV2 and M. hyopneumoniae infection based on clinical, immunological, virological, and pathological evaluations under field conditions.