Clinical evaluation, serological response and lesions generated by the A/Mexico/La Gloria-3/2009/H1N1 and A/swine/New Jersey/11/1976/H1N1 influenza viruses in colostrated and non-colostrated pigs.

Influenza A viruses cause respiratory disease in piglets, and maternal immunity plays an important role in protecting against Influenza virus infection. Nevertheless, in the presence of high levels of maternal antibodies against influenza, an adequate immune response is not developed. In this study, the effect of maternal antibodies against the swine influenza A/swine/New Jersey/11/1976/H1N1 virus (swH1N1) on clinical presentation, serological response, and lesions produced in colostrated and non-colostrated pigs was evaluated in pigs infected with the human influenza A/Mexico/La Gloria-3/2009/ H1N1 (pH1N1) and swH1N1 viruses. Our results indicated that between 2 and 4 days post-challenge, sneezing and mild nasal discharge were observed in all pigs. Body temperature in pigs from all treatment groups ranged between 39.2 and 39.3 °C. Pigs inoculated with the pH1N1 virus (421 g) exhibited a significantly lower daily weight gain than those inoculated with the swH1N1 virus (524 g). HI antibody titers against the pH1N1 virus were significantly different between colostrated (1.62) and non-colostrated (0.43) pigs. Significant differences in antibody titers were detected between pigs inoculated with the pH1N1 (1.28) or the swH1N1 virus (0.77) (P < 0.05). The highest percentage of pulmonary lesions was observed in non-colostrated/pH1N1 pigs (11.88%) at 6 days post-challenge. Cross reactivity was observed between the pH1N1 and swH1N1 viruses, as the maternal antibodies against the swH1N1 virus successfully neutralized the pH1N1 virus infection. © Indian Virological Society 2019.