Submitted to: American College of Veterinary Pathologists Meeting
Publication Type: Proceedings
Publication Acceptance Date: 10/15/2014
Publication Date: 11/8/2014
Citation: Swayne, D.E. 2014. Resurgence of HPAI in birds and mechanisms of transmission. In: Proceedings of the Annual Meeting of the American College of Veterinary Pathologists, November 8-12, 2014, Atlanta, Georgia. Available: http://www.acvp.org/meeting/2014/contributions.cfm.
Technical Abstract: High pathogenicity avian influenza (HPAI) viruses typically produce a similar severe, systemic disease with high mortality in chickens and other gallinaceous birds, but either no disease or only mild disease in domestic ducks and wild birds. However with emergence of H5N1 HPAI viruses and their maintenance in domestic poultry for past 17 years, there has been a shift in virulence within chickens seen as shorter means death times (MDT) and widespread virus replication in vascular endothelial cells. In domestic ducks, H5N1 HPAI viruses have changed from producing inconsistent respiratory infections in 2 week-old domestic ducks to some strains being highly lethal in adult ducks with virus in multiple internal organs and brain. The H5N1 HPAI virus has crossed multiple species barriers to infect domestic poultry, captive and wild birds, carnivorous mammals, and humans. Human infections have been associated with direct or indirect contact with live or dead poultry while in carnivores, consumption of infected birds or their products have been associated with infections. Experimental studies in the ferret and pig demonstrated transmission of H5N1 HPAI virus by oral or direct digestive tract exposure, but required a much higher dose of virus than exposure via the upper respiratory tract. With respiratory trophic H5N1 virus, consumption of infected meat by ferrets initiated infection through the tonsil followed by nasal cavity, but with systemic H5N1 HPAI viruses, simultaneous infection also occurred via the upper digestive tract with spread to liver and pancreas. Slaughter of H5N1 HPAI virus infected asymptomatic chickens, produced air borne virus in large droplets and aerosols, and transmitted the virus to infect and kill chickens and ferrets in same air-space.