The objective was to investigate whether two live–vaccine candidates developed in our lab would provide protection to newly emerging H3N2v swine influenza virus (SIV) infection and control virus transmission in pigs. Two trials were conducted. The first evaluated the pathogenicity and transmissibility of H3N2v SIV. A group of pigs were infected with H3N2v SIV (principal infection group). Then, we brought a group of healthy pigs (contact group) into the same pen to investigate direct–contact transmission. The pigs stayed together for three days. The principal pigs started to shed large amount of virus in nasal mucus at 24 hours post infection. The contact pigs also started to shed virus in nasal mucus at 24 hours after contact with principal group. H3N2v virus infection did not cause fever and other SIV symptoms—coughing, anorexia, depression, but induced lung lesions in both groups. Next we conducted a similar study, but this time the principal pigs were vaccinated twice with various SIV vaccines; FluSure XP or live–SIV vaccines before the H3N2v virus infection. Contact pigs entered the pens of each principal group following virus infection. All vaccine groups developed antibody response to H3N2v virus but only FluSure XP vaccine group induced protective antibodies. That vaccination also reduced the number of pigs shedding virus as well as the amount of shed virus. However, the delayed virus transmission resulted in delayed viral clearance in its contact group.
Key Points:
- Both the commercial and live-SIV vaccines provided partial protection against H3N2v infection.
- However, both failed to effectively control the transmission of H3N2v virus to healthy contact pigs.
- This further emphasizes the importance of continuous surveillance of SIV circulating in swine farms and vaccine updates.
Principal Researcher: Dr. Yan Zhou, University of Saskatchewan