Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 2001
Publication Date: June 3, 2002
Interpretive Summary: Influenza can infect a wide range of animal species including humans, pigs, horses, chickens and turkeys. Typically influenza causes a respiratory infection that in some cases can lead to complications that can be fatal. However, in chickens and turkeys the respiratory form can change to a deadly form called highly pathogenic avian influenza (HPAI). HPAI not only ycauses a respiratory infection, but it infects internal organs which accounts for the deadly nature of the disease. HPAI is not normally found in the U.S., but the respiratory form of the virus, also known as low pathogenic avian influenza (LPAI), occurs commonly in the U.S., and LPAI can mutate to the highly pathogenic form of the virus. One outbreak of LPAI has been in the live bird markets in the Northeast U.S. since 1994, and because of the concern for them becoming highly pathogenic, they have been monitored closely. This paper describes a new diagnostic technique that allows researchers to quickly identify which viruses need to be studied in more detail. It is important to identify these variant viruses quickly so that if HPAI occurs, we can identify and eradicate it quickly.
Technical Abstract: Highly pathogenic avian influenza (HPAI) in poultry causes high morbidity and mortality and it is a List A disease of the Office International des Epizooties. An outbreak of HPAI in commercial poultry causes not only direct disease losses, but often results in trade restrictions for the affected country. Since HPAI viruses can mutate from H5 and H7 low pathogenic avian influenza (LPAI) viruses, it is necessary to monitor and control even the low pathogenic form of the virus. We report a practical approach for screening large numbers of isolates that uses amplification by reverse transcriptase-polymerase chain reaction (RT-PCR) of a segment of the hemagglutinin (HA) gene (536-560 bp) of H7 AIVs followed by the heteroduplex mobility assay (HMA). The HMA test compares the amplified PCR product from unknown samples to reference isolates that allows the identification of new variants. The HMA test results were compared with sequence analysis of the isolates used in the study. On the basis of the HMA, we could identify several new variant viruses present in the live bird markets (LBMs) in the Northeast United States. New strains gave a distinct pattern of bands in the gels in accordance with the different heteroduplexes formed when their HA region amplification products were incubated together with the same amplification product of a reference strain. These differences correlate with phylogenetic analysis.