AN UNEXPECTED SEROLOGY PROFILE AFTER SWINE INFLUENZA VIRUS (SIV) INFECTION IN A PORCINE RESPIRATORY DISEASE COMPLEX (PRDC) OUTBREAK
M. Terrini

Abstract
Swine Influenza has been recognised in Italy since 1980. It has a well known role in PRDC and its presence on farms nationwide has been confirmed over the last few years. All three subtypes H1N1, H3N2 and H1N2 are present and, in some situations, can co-exist on the same farm. The author reports a case of PRDC, with SIV, that was experienced on a 400 farrow-to-finish unit. The outbreak began with most of the growers affected and presenting the typical clinical picture of SIV. About 10 days later, the mortality rate increased. The analyses made confirmed the presence of H1N2, as well as some secondary bacterial infections. The serological profile showed an unexpected lack of seroconversion for H1N2 in the paired samples. When a homologous strain was substituted for the original routine virus used in the HI test, seroconversion was then evident. Serology is more appropriate for monitoring programmes, while virus identification is recommended for diagnosis in new outbreaks.

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