Highly Pathogenic Avian Influenza: Intersecting Humans, Animals, and the Environment

Authors: Pantin Jackwood, Mary; Swayne, David; Suarez, David

Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: 11/5/2010
Publication Date: 11/16/2010
Citation: Pantin Jackwood, M.J., Swayne, D.E., Suarez, D.L. 2010. Highly Pathogenic Avian Influenza: Intersecting Humans, Animals, and the Environment [abstract]. One Health in Action 2010 ARS Animal Health Research Review at the United States Animal Health Association 114th Annual Meeting/American Association of Veterinary Laboratory Diagnosticians 53rd Annual Converence, November 11-17, 2010, Minneapolis, MN. CD-ROM.

Interpretive Summary:

Technical Abstract: The Eurasian-African H5N1 highly pathogenic avian influenza (HPAI) virus has caused an unprecedented epizootic affecting mainly poultry, but has crossed multiple species barriers to infect captive and wild birds, carnivorous mammals and humans. There is still great concern over the continued infection of humans with H5N1 HPAI. 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 were conducted in mammals to better understand the modes of exposure that favor transmission of the H5N1 HPAI virus. Of the four mammalian models examined, the ferret and pig demonstrated transmission of H5N1 HPAI virus by oral or direct digestive tract exposure and most closely mimicked human infections and disease, but production of infection by oral or direct digestive tract exposure required a much higher dose of virus than exposure via the upper respiratory tract. The predominant site of virus replication following oral consumption of H5N1 virus infected meat was the respiratory tract, initiated through infection of tonsil followed by nasal cavity infection, but with some viruses in ferrets, simultaneous infection also occurred via the upper digestive tract with spread to liver and pancreas. Theoretical modes of transmission of avian influenza viruses from birds-to-humans would include: 1) inhalation of contaminated dust from rearing or outdoor slaughter, or fine water droplets generated during household or live poultry market slaughter process; 2) direct contact with oral, nasal or conjunctival mucus membranes such as from hand-transplantation of virus from contaminated surfaces, direct exposure to contaminated dust or feathers, or swimming or bathing in contaminated household water source; and 3) consumption of raw or undercooked infected poultry products. However, considering the rarity of cases associated with eating raw infected products and the ease of killing avian influenza by cooking, HPAI has not become a food safety issue. However in recent experimental studies, an H5N1 HPAI virus was transmitted to ferrets and chickens by exposure to airborne virus generated during simulated home slaughter of asymptomatic infected chickens. The H5N1 HPAI virus was detected in the slaughter room air samples. Usage of vaccinated chickens in similar studies blocked H5N1 HPAI virus transmission to ferrets and no H5N1 HPAI virus was isolated from air samples taken from in the slaughter room. In addition, conducting the slaughter step of H5N1 HPAI virus-infected non-vaccinated chickens in a plastic bag greatly reduced the virus transmission through the air to ferrets. Such intervention also reduced the number of virus-positive air samples and the titer of virus in those positive samples. In order to reduce the risk of zoonotic infection with H5N1 HPAI virus, the specific types of contacts and activities leading to transmission need to be furthered studied, as well as virological and ecological aspects, and viral persistence in the environment.