#03-162

Complete

Date Full Report Received

08/29/2005

Date Abstract Report Received

12/20/2006

Investigation

Institution:
Primary Investigator:

Respiratory disease caused by swine influenza virus (SIV) has become a serious health and economic problem to the U.S. swine industry. Prior to 1998, SIV in the U.S. swine population consisted of viruses of the H1N1 subtype comprised of swine genetics. In 1998, a new subtype of the virus emerged, a H3N2 virus that was made up of genetics from avian and human influenza lineage in addition to the swine lineage of the original virus. The emergence of this virus has resulted in new isolates that differ both genetically and antigenically from the original virus as well as showing continuous evolution to new antigenic types. As a result, diagnostics and disease control have become more problematic to the swine industry. The goal of the research reported here was to evaluate the ability of the different serological assays to detect SIV viruses that differ in genetic makeup both by subtype and within subtype. This study demonstrated that different viruses of both the H1 and H3 hemagglutinin subtypes have different cross-reactivity based on the virus used as the test antigen in the HI assay. The results of measuring SN antibodies, thought to be important in disease control, showed similar patterns as with the HI assay. However, the levels of SN antibodies were not tightly correlated with the HI results and further complex statistical analysis is ongoing to determine this relationship. The commercial ELISA assay detected antibodies to all viruses that were of the H3 subtype, but was less consistent in detecting antibodies to the H1 subtype. Antibodies to two of the H1 viruses, a H1N1 and a H1N2, were not detected by the ELISA, raising a concern about the sensitivity of the test as both of these viruses showed low levels of antibodies measured by both the HI and SN assays. The sera created in this study will be available to researchers and diagnostic laboratories to use in developing and evaluating the prevalence and cross-reactivity between SIV viruses. It is hoped that the information obtained here will aid producers and veterinarians in accurately diagnosing SIV infection within swine herds and facilitate vaccine development and selection to further enhance disease control.