Submitted to: Pig Veterinary Society International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/30/2010
Publication Date: 7/18/2010
Citation: Opriessnig, T., Madsen, D.M., Shen, H., Brockmeier, S., Beach, N., Meng, X.J. 2010. PCV2 Vaccination Prevented Clinical PCVAD and Reduced PCV2 Viremia and Semen Shedding in Boars Concurrently Infected with PCV2b and Mycoplasma hyopneumoiae. In: Proceedings of the Pig Veterinary Society International Congress, July 18-21, 2010, Vancouver, Canada. p. 427. Interpretive Summary:
Technical Abstract: Introduction. It has been determined that porcine circovirus type 2 (PCV2) DNA is shed in semen of naturally and experimentally infected boars (1). Recently, it also has been shown that PCV2 DNA present in semen is infectious in a swine bioassay model (2). However, under experimental conditions the amount of PCV2 shed in semen is low and not sufficient to be transmitted into naive breeding animals (2). In the growing pig model, Mycoplasma hyopneumoniae infection has shown to potentiate PCV2 replication, PCV2-associated lesions, and disease (3). Under field conditions, young boars that enter boar studs are often exposed to infectious agents (i.e. M. hyopneumoniae) for the first time, are given multiple adjuvanted vaccines, and are exposed to other stressors (mixing, transportation) that are thought to enhance PCV2 replication in growing pigs. The main objective of this study was to determine if the amount of PCV2 shed in semen can be increased in boars experimentally coinfected with M. hyopneumoniae and immune-stimulated via killed parvovirus-leptospira-erysipelothrix (PLE) vaccination. In addition, we wanted to determine if PCV2 vaccination of the boars prior to PCV2 exposure will reduce PCV2 viremia and PCV2 shedding in semen. Materials and Methods. Twelve specific-pathogen-free PCV2 and M. hyopneumoniae naive boars were randomly divided into one of four groups with three animals in each group. Half of the boars were vaccinated against PCV2 35 days before PCV2 challenge using a commercially available inactive product (Suvaxyn® PCV2; Fort Dodge Animal Health). Fourteen days before and at the day of PCV2 inoculation all 12 boars were vaccinated with a commercially available PLE vaccine (FarrowSure®, Pfizer Inc.). In addition, 14 days before PCV2 inoculation, 6/12 boars were intranasally inoculated with M. hyopneumoniae. All boars were challenged with PCV2b on Day 0 of the study. Semen and serum samples were collected on a weekly basis and all boars were euthanized 35 days post PCV2 inoculation. All samples were analyzed for the presence of anti-PCV2 IgG antibodies by ELISA and for presence and amount of PCV2 DNA by quantitative real-time PCR as described (1). Results. All vaccinated boars had seroconverted to PCV2 by the time of PCV2 challenge, whereas non-vaccinated boars were seronegative. After M. hyopneumoniae challenge, inoculated boars developed moderate respiratory disease characterized by coughing, respiratory distress, and mucopurulent nasal discharge. After PCV2 challenge, one of three coinfected, non-vaccinated boars became lethargic, lost condition, and died. M. hyopneumoniae infected boars had significantly (p<0.05) higher PCV2 DNA levels in serum compared to boars singularly infected with PCV2. Non-vaccinated boars had significantly (p<0.05) higher PCV2 DNA loads in serum compared to vaccinated boars. Moreover, PCV2 vaccination resulted in significantly (p<0.05) reduced incidence of shedding of PCV2 in semen. Discussion. In this study we showed that boars experimentally infected with PCV2 and M. hyopneumoniae can develop clinically manifest porcine circovirus associated disease (PCVAD). In addition, PCV2 vaccinated boars did not develop clinical disease and had significantly reduced PCV2 viremia and PCV2 shedding in semen. This information will guide boar stud owners in their decision process when considering PCV2 vaccination. Acknowledgments. This works was funded by the Iowa Livestock Healthy Initative. We thank Shayleen Harrison for assistance with the animal work. References 1. Madson, D.M. et al. (2008) J. Vet. Diagn. Invest. 20, 725-734. 2. Madson, D.M. et al. (2009) Vet. Res. 40:10. 3. Opriessnig, T. et al. 2004. Vet. Pathol. 41: 624-640.