Swine influenza: clinical, serological, pathological, and virological cross‐sectional studies in nine farms in Argentina

Abstract

BackgroundInfluenza A viruses (IAV) are important pathogens responsible for economic losses in the swine industry and represent a threat to public health. In Argentina, clinical, pathological, and virological findings suggest that IAV infection is widespread among pig farms. In addition, several subtypes of IAV, such as pH1N1, H3N2, δ1H1N1, and δ2H1N2, have been reported.ObjectivesTo evaluate the infection patterns of influenza virus in nine pig farms in Argentina.MethodsClinical, serological, pathological, and virological cross‐sectional studies were conducted.ResultsClinical and pathological results were characteristic of endemic influenza infection in eight of the nine farms studied. By rRT‐PCR, six of the nine farms were positive to influenza. Five IAV were obtained. Genome analysis determined that four of the isolations were pH1N1 and that the remaining one was a reassortant human origin H3N2 virus containing pandemic internal genes. Serological results showed that all farms were positive to influenza A antibodies. Moreover, the hemagglutination inhibition test showed that infection with viruses containing HA′s from different subtypes (pH1, δ1H1, δ2H1, and H3) is present among the farms studied and that coinfections with two or more subtypes were present in 80.5% of positive pigs.ConclusionsBecause vaccines against IAV are not licensed in Argentina, these results reflect the situation of IAV infection in non‐vaccinated herds. This study provides more information about the circulation and characteristics of IAV in a poorly surveyed region. This study provides more data that will be used to evaluate the tools necessary to control this disease.

Two years of surveillance of influenza a virus infection in a swine herd. Results of virological, serological and pathological studies

“…In these farms, IAV infections are considered a nursery problem mostly affecting successive batches [3]. Previous serological and virological characterization studies showed that influenza virus strains that circulate in pigs in Argentina are not related to those reported in pigs elsewhere in the world with the exception of the H1N1p virus [3,8,17].…”

“…The rRT-PCR was performed in an ABIPrism® 7500 SDS apparatus (Applied Biosystems ™ , Foster City, CA, USA). Samples corresponding to the rRT-PCR positive pools were further processed for virus isolation in Madin-Darby Canine Kidney cells (MDCK) as described previously [3]. vRNA was extracted from the positive culture supernatant and used to PCR amplify the HA, NA and M gene segments.…”

“…IAVs of H1N1, H3N2, and H1N2 have been commonly detected in commercial swine populations around the world including Argentina [1–3]. Within each of these subtypes, numerous antigenic and reassortant variants are found.…”

“…Introduction of a new IAV in a swine herd typically produces an epidemic [2] followed by endemic and/or subclinical infections that can persist for long periods of time [3,6,7]. The pandemic H1N1 virus in 2009 (H1N1p) likely originated in swine and contained a constellation of gene segments derived from multiple reassortment events involving swine-, human-, and avian-origin IAV strains.…”

“…The subsequent spillover of such virus back into pigs, had led to more intensive swine influenza surveillance efforts worldwide, particularly in commercial swine operations [1,8]. Several studies have suggested that influenza infection is far more common than suggested by confirmed clinical outbreaks [3,6,7,9]. IAV persistence in endemically infected herds is not well understood [7].…”