A Dual Swine Challenge With Porcine Circovirus Type 2 (PCV2) and Mycoplasma hyopneumoniae Used to Compare a Combination of Mixable Monovalent PCV2 and Monovalent M. hyopneumoniae Vaccines With a Ready-to Use PCV2 and M. hyopneumoniae Bivalent Vaccine

Abstract

The present study evaluated the efficacy of swine vacciation using a combination of mixable monovalents for porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae against a ready-to-use bivalent vaccine under experimental conditions. Pigs at 21 days of age were administered either a combination of two mixable monovalent vaccines or a bivalent vaccine containing PCV2 and M. hyopneumoniae. Vaccination was followed with an M. hyopneumoniae challenge at 42 days of age (-14 days post challenge, dpc) and a PCV2d challenge at 56 days of age (0 dpc). Each vaccinated and challenged group was compared with the unvaccinated and challenged group for clinical, microbiological, immunologic, and pathologic differences. Clinically, two vaccinated and challenged groups showed minimal respiratory diseases that was characterized by occasionally coughing and sneezing. A significant difference was not calculated in the average daily weight gain, nasal shedding of M. hyopneumoniae, and pathological lesions between two vaccinated and challenged groups. A combination of two monovalent vaccines mixed into a combo prior to vaccination followed by challenge resulted in increased numbers of PCV2d-specific interferon-γ secreting cells at 21 dpc and a significant reduction in PCV2d viremia at 14 dpc when compared with the ready-to-use bivalent-vaccinated and challenged groups. These results offer supporting evidence that vaccination during the weaning to finishing period against M. hyopneumoniae and PCV2 is efficacious for controlling diseases caused by these two pathogens.

Keywords: Mycoplasma hyopneumoniae; bivlent vaccine; dual challenge; porcine circovirus type 2; porcine respiratory disease complex; swine; vaccination.

Figure 1

Clinical resipiratory sign. Clinical respiratory sign scores in the different groups: VacA/Ch (•), VacB/Ch (•), UnVac/Ch (•), and UnVac/UnCh (▴). Different letters within a sampling point mean statistically significant differences (P < 0.05). Variation is expressed as the standard deviation. Different letters within a sampling point mean statistically significant differences (P < 0.05).

Figure 2

Genomic quantification. (A) Mean values of the genomic copy number of Mycoplasma hyopneumoniae (Mhyo) DNA in nasal swabs. (B) Mean values of the genomic copy number of porcine circoviorus type 2d (PCV2d) DNA in serum in the different groups: VacA/Ch (•), VacB/Ch (•), UnVac/Ch (•), and UnVac/UnCh (▴). Different letters within a sampling point mean statistically significant differences (P < 0.05). Variation is expressed as the standard deviation. Different letters within a sampling point mean statistically significant differences (P < 0.05).

Figure 3

Immune responses against Mycoplasma hyopneumoniae (Mhyo). (A) Mean values of the Mhyo ELISA antibodies. (B) Frequency of Mhyo-specific interferon-γ secreting cells (IFN-γ-SC)/10⁶ peripheral blood mononuclear cells (PBMC) in the different groups: VacA/Ch (•), VacB/Ch (•), UnVac/Ch (•), and UnVac/UnCh (▴). Variation is expressed as the standard deviation. Different letters within a sampling point mean statistically significant differences (P < 0.05).

Figure 4

Immune responses against porcine circovirus type 2 (PCV2). (A) Mean values of the PCV2 ELISA antibodies. (B) Frequency of PCV2d-specific interferon-γ secreting cells (IFN-γ-SC)/10⁶ peripheral blood mononuclear cells (PBMC) in the different groups: VacA/Ch (•), VacB/Ch (•), UnVac/Ch (•), and UnVac/UnCh (▴). Variation is expressed as the standard deviation. Different letters within a sampling point mean statistically significant differences (P < 0.05).