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

Influenza-like clinical signs were mild in all pigs. No pigs died during the study due to influenza infection, and only one contact pig from the HE group had to be removed from the study due to arthritis. The odds of a pig displaying a clinical sign (fever, lethargy, coughing, sneezing, nasal discharge, or dyspnea) during the first week of exposure was significantly lower in the HE group than in NV pigs (OR = 0.37, 95% CI 0.21-0.65, p = 0.005). Macroscopic and microscopic lung lesions NV pigs had pneumonia with areas of lung consolidation at necropsy, and the mean (± SD) lung lesion score was 8.86 ± 7.1%. Thirty-one of the 40 pigs in the HE group and sixteen of the 30 pigs in the HO group had some degree of lung consolidation. The mean lung lesion score for the pigs in the HE group was significantly higher (p ≤ 0.05) than the mean for the pigs in the HO group (5% ± 8 vs. 1.7% ± 5.1) at necropsy.