Occurrence of a Pig Respiratory Disease Associated with Swine Influenza A (H1N2) Virus in Tochigi Prefecture, Japan

摘要

In February 2008, a feeder pig herd of the affected Firm in Tochigi Prefecture. Japan, showed increasing respiratory symptoms: by April, the situation worsened with 12-16 pigs dying daily. Diagnostic tests revealed the presence or H1N2 subtype of swine influenza virus (SI V) and Pasteurella multocida from nasal swab and lung emulsion. Serological tests by hemagglutaination inhibition method and enzyme-linked immunosorbent assay method (ELISA: imported from U.S.A.) indicated the spread of SIV into the pig herds of the affected Farm around April 2008. The severe infection and subsequent damage were considered as a result of the combined infection 01 SI V (H1N2) and bacteria that may have been prevalent in the pig farm. Genetic homology search of sequences for the hemagglutinin (HA) and neuraminidase (NA) genes of A/swine/Tochigi/1/08 showed high homology to Japanese SIVs (H1N2) isolated in the 2000s. Therefore, we considered that Japanese SIV (H1N2) has established an independent stable lineage and participated in in pig populations as one of the factors of the pig respiratory disease complex. Consistent surveillance would contribute to clarifying the prevalence of dominant SIVs.