US pork industry’s first vaccine with two PCV2 genotypes announced at AASV
The US pork industry’s first vaccine to include two genotypes of porcine circovirus type 2 (PCV2) — 2a and 2b — was announced on the first day of the American Association of Swine Veterinarians conference in San Diego.
Together, the two genotypes in the vaccine, Fostera Gold PCV MH, provide the broadest range of protection against evolving PCV2 viruses in US swine herds, Lucina Galina, DVM, PhD, director, swine technical services, Zoetis, told veterinarians at a special launch event.
Furthermore, the vaccine’s efficacy against 2d — the most prevalent PCV2 genotype — was demonstrated in a large field trial.
“We’re pleased to introduce a vaccine that brings real value to the US pork industry — one that provides broader protection against PCV2 genotypes and, more importantly, helps to minimize performance problems due to the virus, reduce monetary losses for producers and benefit animal welfare,” she added.
The duration of immunity (DOI) with the new vaccine is at least 23 weeks for PCV and Mycoplasma hyopneumoniae (M. hyo), which means the vaccine will protect most herds through the finishing period. Its DOI for PCV2 is the longest of any commercial vaccine of its kind in the US.
The vaccine may be administered as a single 2-ml dose from 3 weeks of age or as a split dose with two, 1-ml doses administered 3 weeks apart. “The split-dose regimen can be initiated as early as 3 days of age, but based on field experience with PCV vaccines, we advise either one dose from 3 weeks of age or the two-dose regimen starting at 3 weeks of age,” Galina said.
Broader protection
The most prevalent PCV2 genotypes currently circulating in US herds are PCV2d followed by PCV2b and PCV2a, according to the latest data from Iowa State University’s Veterinary Diagnostic Lab.1
Other commercial PCV2 vaccines contain either the PCV2a or PCV2b genotype, but not both. While traditional PCV2 vaccines have provided acceptable cross protection against 2d in many herds, it has sometimes been insufficient, Galina reported in a presentation at the American Association of Swine Veterinarians conference.
“And the percentage of herds with subclinical or undetected PCV2 could grow as the virus evolves and evades conventional PCV2 vaccination programs,” she added.
The new vaccine from Zoetis protects against 2a and 2b and, in a field trial, showed additional cross protection against the highly prevalent 2d.2 Phylogenetic analysis has demonstrated that 2b and 2d are closely related; 2d was once called “mutant 2b.” Antibodies and immune cells such as lymphocytes against 2b also recognize 2d.3
Field-trial efficacy
The comparative field trial that demonstrated the efficacy of the vaccine against 2d involved 880 pigs housed at a commercial facility in the Midwest.4
More than 300 pigs received a regimen of Fostera Gold PCV MH or other commercially available PCV2 plus M. hyo vaccines. An additional unvaccinated group served as a control. Two weeks after vaccination, pigs were challenged with M. hyo and then with PCV2d one week later.
Investigators found that viremia, which reflects the level of virus in blood and is associated with disease protection, was significantly better controlled (p < 0.05) with one- and two-dose regimens of the new vaccine compared to unvaccinated control pigs.
Immunohistochemistry — a process that shows how antibodies bind to antigens — revealed 0% PCV2 in pigs that received two doses of the new vaccine started at weaning. These results were significantly different compared to PCV2 in 46% of unvaccinated controls and in 21% of pigs that received another two-dose commercial vaccine initiated at 3 days of age.
In addition, investigators observed significantly fewer (p < 0.05) lung lesions in pigs that received one- or two-dose regimens of the new vaccine compared to pigs that received one dose of another PCV2 plus M. hyo vaccine at weaning. The latter group had more lung lesions than unvaccinated pigs.5
By study-day 157, average weight in pigs that received one weaning dose of the new vaccine was 257 pounds, and in pigs that received two doses initiated at weaning, it was 254. These results were significantly better (p < 0.05) compared to an average weight of 242 pounds for unvaccinated controls and numerically better compared to other vaccine groups.
More advantages
The trial demonstrated the new vaccine has a high margin of safety. One pig that received the vaccine had a local reaction, which was minor. The vaccine’s safety is attributed to the adjuvant, MetaStim®, which Zoetis said is gentle on pigs yet stimulates both antibody and a strong cell-mediated immune response. This is important, Galina explained, because cell-mediated immunity is key to protecting pigs against diseases caused by PCV2 and M. hyo.
PCV2 infection remains widespread in the swine industry, according to reports from the Iowa State University Veterinary Diagnostic Laboratory. The disease is often subclinical, leading to poor growth that increases days to market. It is also a component of other complex disease problems such as Porcine Reproductive and Respiratory Complex. If uncontrolled, PCV2 can cost producers on average $3 to $4 per pig with peak losses up to $20 per pig.6
Editor’s note: Read Pig Health Today’s recent interview with Rick Swalla, DVM, about the significance of the new vaccine.
1. Personal communication, Darin Madson, DVM, PhD, to Rick Swalla, DVM.
2. Data on file, Study Report No. 16PRGBIO-01-01, Zoetis LLC.
3. Lekcharoensuk P, et al. Epitope mapping of the major capsid protein of type 2 porcine circovirus (PCV2) by using chimeric PCV1 and PCV2. J Virol. 2004 Aug;78(15):8135-8145.
4. Data on file, Study Report No. 16PRGBIO-01-01, Zoetis LLC.
5. Ibid.
6. Gillespie J, et al. Porcine circovirus type 2 and porcine circovirus-associated disease. J Vet Intern Med. 2009;23:1151-1163.
Posted on March 3, 2018
