S. Ma1, A. Venegoni1, M. Sheeder2, M. Titus3, L. Kesl3, R. Saltzman3
1Research and Development, Pharmgate Animal Health, Wilmington, NC; 2Struve Labs, Manning, IA; 3Veterinary Resources Inc, Ames, IA
Porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (Mhp) reduce weight gain and cause increased morbidity and mortality either alone or in combination with other pathogens. In this study, we evaluate the efficacy and safety of 2 adjuvant compositions for a new 1-mL single dose PCV2/Mhp vaccine (Circo/MycoGard®) in growing pigs vaccinated at 13 days of age.
Materials and Methods
Four challenge studies were conducted to separately evaluate vaccine adjuvant compositions efficacy against both PCV2 and Mhp. In the PCV2 studies, 4 groups of 21 CDCD pigs were either vaccinated with 1 mL of Circo/MycoGard® adjuvanted with StimGard Plus® or StimGard®, or placebos at 13 days of age. Pigs were blocked by litter and randomly assigned to either group. Pigs were challenged with PCV2 31 days post-vaccination (~3 weeks after weaning). Challenge material consisted of the administration of a 2-mL mix of 2 PCV2 isolates both intranasal- and intramuscularly. PCV2 viremia and ELISA S/P ratios were determined weekly for 4 weeks post-challenge. Lymphoid tissue immunohistochemistry and lymphoid depletion scores were assessed at the end of the study (28 days post-challenge) in 3 lymph nodes and tonsils of each pig. In the Mhp studies, 4 groups of 21 Mhp-negative pigs had the same vaccination schedule as in the PCV2 studies. Pigs were challenged with an intratracheal inoculation of 18 mL of a lung homogenate inoculum containing Mhp strain 232 at 33 days post-vaccination. Percentage of macroscopic lung lesions were assessed after necropsy at 37 days post-challenge. Clinical signs and injection site reactions were scored daily post-challenge in all studies. Wilcoxon rank sum and Fisher’s Exact tests were used to compare among Circo/MycoGard® adjuvant compositions and placebo groups.
PCV2 viremia (Log10 DNA copies/mL) over time was lower with Circo/MycoGard® adjuvanted with StimGard Plus® (CMG StimGard Plus®) compared to Circo/MycoGard® adjuvanted with StimGard® (CMG StimGard®), and the placebo groups as shown in Fig 1. PCV2 immunohistochemistry and lymphoid depletion microscopic total sum scores of each pig were lower with Circo/MycoGard® adjuvanted with StimGard Plus® compared to the other groups (p-values<=0.06). PCV2 ELISA S/P ratios after challenge were not significantly different between the Circo/MycoGard® adjuvant compositions and both were significantly higher than the placebos. Clinical signs scores after challenge were not significantly different among all groups. In the Mhp challenge studies, percentages of macroscopic lung lesion were lower with Circo/MycoGard® adjuvanted with StimGard Plus® (CMG StimGard Plus®) in comparison to Circo/MycoGard® adjuvanted with StimGard® (CMG StimGard®) (p-value=0.13). Clinical signs scores were not different between all groups. There were no observable injection site reactions in any of the groups in all studied pigs.
Conclusions and discussion
The new 1-mL single dose PCV2/Mhp vaccine (Circo/MycoGard®) adjuvanted with StimGard Plus® was safe and more efficacious against PCV2 and Mycoplasma hyopneumoniae challenges in growing pigs vaccinated at 13 days of age.