Observations regarding influenza A virus shedding in a swine breeding farm after mass vaccination

An outbreak of respiratory disease in suckling piglets started in December 2010 in a 1200-sow farrow-to-wean facility. Swine influenza virus H1N2 was isolated from nasal swabs of affected piglets and determined to be the cause of the respiratory disease. After 2 months of continuous respiratory disease in the suckling-piglet and nursery populations, a change in the influenza vaccination strategy was adopted. Administration of swine influenza autogenous vaccine at 85 to 91 days of gestation was discontinued, and mass vaccination of the breeding herd was performed with two doses of a commercial multivalent vaccine. Prevalence of virus shedding was monitored by real-time reverse transcriptase polymerase chain reaction assay in nasal swabs and oral fluids from sows and suckling piglets before and after mass vaccination. After vaccination, there was a significant increase {P < .001) in hemagglutination inhibition serum-antibody titers in breeding females. Prevalence of shedding in sows and suckling piglets decreased through the 13 weeks of monitoring until no influenza-positive samples were detected in suckling and recently weaned pigs. This case report provides insights into a potential control strategy for swine influenza in breeding herds through mass vaccmation.