Author
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Swayne, David |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 12/1/2006 Publication Date: 6/11/2008 Citation: Swayne, D.E. 2008. Avian influenza. Foreign Animal Diseases, 7th Edition. St. Joseph, Missouri. U.S. Animal Health Association. p. 137-143. Interpretive Summary: Technical Abstract: Avian influenza (AI) is a viral infection of birds that varies in severity from asymptomatic infections to mild respiratory and reproductive diseases to an acute, highly fatal systemic disease of chickens, turkeys, guinea fowls, and other avian species. Avian influenza viruses are divided into two broad pathotypes, low (LP) and high pathogenicity (HP), based on experimental studies in chickens. AI viruses are further categorized, based on the two surface glycoproteins, into 16 different hemagglutinin (H1-16) and 9 different neuraminidase (N1-9) subtypes. LPAI viruses can be any of the 16H and 9N subtypes but HPAI viruses have only been of H5 and H7 subtypes. All H5 and H7 LP and HPAI are notifiable AI (NAI) to the World Organization for Animal Health. Most avian species appear to be susceptible to at least some of the NAI viruses. Ecological data indicated various migratory waterfowl, sea birds, and shore birds are the reservoir for all NAI virus genes. In addition, epidemiological and molecular genetic evidence supports the hypothesis that these aquatic birds are generally responsible for introducing the LPNAI viruses into poultry through fecal contamination of poultry premises. Once introduced into poultry, the viruses adapt to poultry and are spread from flock-to-flock or village-to-village by human endeavor such as movement of infected birds and contaminated equipment, shoes, clothing, egg flats, feed trucks, and any service crews, to mention a few. Clinical signs, lesions and death rates vary depending on the virus strain, host species and other factors. The best strategy for controlling NAI is eradication. This is achieved through comprehensive control strategies that utilize inclusion and exclusion biosecurity practices, diagnostics and surveillance, elimination of infected animals, increasing host resistance, and education of personnel in AI control strategies. The level of incorporation and practice of these five components will determine whether the control strategy will be effective at eradicating AI or prevent its introduction. |
