Vaccination of influenza a virus decreases transmission rates in pigs

Romagosa, Anna; Allerson, Matt; Gramer, Marie; Joo, Han Soo; Deen, John; Detmer, Susan; Torremorell, Montserrat

Other experimental transmission studies with H7N7 avian influenza virus, PRRSV and Aujeszky's disease were not able to correlate the amount of virus excreted by infected pigs with increased values in the transmission parameter β [20, 31, 51] . In our study, the initial infectiveness was similar in all the groups due to the use of unvaccinated and experimentally inoculated seeder pigs under the same experimental conditions. Also, no statistically significant differences were observed in TCID 50 values at the time of exposure with the contact pigs and the infectious period was similar for all seeder pigs. Therefore, differences in transmission between groups can be attributed to the decrease in susceptibility of the contact pigs to become infected, and the length of the IP between groups. The infectious period was one day shorter in the HE group than in the NV group and that could play a role in the value of R and account for some of the differences observed between replicates. Overall, detection of influenza virus in the HE vaccinated population lasted longer than in the NV population which also highlights the role of partially immune populations as potential sustained reservoirs for influenza infections.