Background: The field efficacy of a bivalent vaccine containing porcine circovirus type 2b (PCV2b) and Mycoplasma hyopneumoniae was evaluated on three pig farms.
Methods: Three pig farms were used, two of which had a history of subclinical PCV2 and clinical M. hyopneumoniae infections between 84 and 126 days of age while concurrent porcine circovirus-associated disease and clinical M. hyopneumoniae infection between 70 and 105 days of age. Each farm vaccinated pigs with a single dose of a bivalent vaccine at 10 days of age while unvaccinated pigs were administered a single dose of phosphate buffered-saline at the same age.
Results: Vaccination improved growth performance and reduced clinical scores significantly (p < .05) when compared with unvaccinated animals. The amount of PCV2d loads in blood and M. hyopneumoniae loads in nasal swabs of vaccinated animals were also significantly lower (p < .05) when compared with unvaccinated animals. Immunologically, vaccinated groups elicited a significantly higher (p < .05) level of protective immunity against PCV2d such as neutralizing antibodies and interferon-γ secreting cells (IFN-γ-SC), as well as protective immunity against M. hyopneumoniae such as IFN-γ-SC when compared with unvaccinated animals. Pathologically, vaccination significantly lowered (p < .05) the scores of M. hyopneumoniae-induced pneumonia and PCV2-associated lymphoid lesions when compared with unvaccinated animals.
Conclusions: The evaluated bivalent vaccine provided good protection against PCV2d and M. hyopneumoniae infection under field conditions.
Keywords: Mycoplasma hyopneumoniae; enzootic pneumonia; porcine circovirus type 2; porcine circovirus-associated disease; subclinical porcine circovirus type 2 infection.
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