Avian Influenza (AI)
Rules and Regulations of the State of New York
AI virus is an RNA virus (orthomyxovirus) and, as is typical of influenza viruses, often mutates producing different strains. As the virus infects and replicates in successive hosts it recombines genes with any other available influenza virus in unpredictable ways. The different strains are labeled according to the types of 2 proteins (Hemagglutinin and Neuraminidase) on the surface of the virus that are instrumental in the virus ability to penetrate a cell and replicate itself. There are 16 different H types and 9 different N types so a multitude of combinations are possible e.g. H1N1, H7N2, H6N9 and etc.
Different strains of AI virus differ radically in their ability to cause illness
in infected birds and are generally divided into Low-Pathogenic
strains (LPAI) which cause minimal to no clinical signs and Highly-Pathogenic
strains (HPAI) which kill 90-100% of infected birds. The H5 and
H7 subtypes of AI are the strains usually responsible for the generation
of an HPAI outbreak in birds. In poultry, AI has been the most devastating
and expensive disease ever confronted by animal health officials
in the U.S.
Figures from November 1983 to April 1984 (Pennsylvania AI outbreak)
reflect a $225 million dollar negative impact on the combined egg,
broiler, turkey and chicken industry.1 A significant and very real
concern is that the less virulent forms of the virus (which are
identified fairly regularly) will mutate into a more virulent and
deadly form of the virus.
Avian influenza (AI) is a disease that can cause illness in many species of
domestic and wild birds. The natural reservoir for AI virus is wild
waterfowl and shorebirds which can carry and transmit the virus
generally without getting sick themselves. Usually AI virus only
infects birds however, the pig has receptors on the surface of its
cells that are compatible with both avian and mammalian influenza
viruses and has traditionally been viewed as the mixing vessel
where these viruses can exchange genes and create new strains capable
of infecting people. Strains of influenza that have caused large
human outbreaks in the past, known as pandemics,
often have had a mixture of avian, swine and human genes reflecting
this pathway of development of the virus from birds, through pigs
Before 1995 it was believed that AI never infected people directly from birds
but an outbreak of a Highly-Pathogenic H5 type in Hong Kong and
China demonstrated the capability of this strain to make that leap.
Since then, there have been several other cases of either H5 or
infecting humans directly and causing disease ranging from mild
eye symptoms to deaths.
Recent interest has been focused on the presence of a highly pathogenic
avian influenza virus in Asia. This virus has been found in
countries in Southeast Asia and more recently in some European countries.
This virus has not been found in New York or in
the United States. Concerns have been raised because of the
associated finding of 117 human cases resulting in 60 deaths (as
of October 10, 2005). The majority of these cases had direct contact
with poultry and it is believed that they acquired the virus through
this contact. There is more limited evidence to support person-to-person
transmission. In all of the outbreaks where humans have been infected
directly from birds:
- the strain of AI has always been of the H5 or H7 Highly-Pathogenic type
- there have only been a small number of human cases compared to the multitude of people exposed (an exact number is not known and could range from thousands to millions)
- the HPAI strain has not been able to readily transmit from person to person
- there has been no evidence of the HPAI becoming more adapted to humans or more virulent for humans
Surveillance and Control of AI in New York
The New York State Department of Agriculture and Markets has had ongoing surveillance for avian influenza, especially within the live bird market system in the New York City area, since 1998. All isolations of avian influenza from this system are characterized and the virus is typed. In 2004 over 10,000 birds were tested without finding any evidence of a highly pathogenic avian influenza virus of any type in this marketing system. So far in 2005 even more birds have been tested with no evidence of any highly pathogenic avian influenza virus.
In addition to testing for the presence of avian influenza viruses in the markets as well as on commercial and backyard poultry farms, since 1998 New York has required that every flock of birds moving into the live bird marketing system be tested and found negative for avian influenza before these birds can be moved into the markets. Inspectors visit the markets for periodic checks of sanitation and sampling inspections and continue to monitor for the presence of ill birds.
Signs of Disease
Depending on the strain of virus that infects the bird, the signs of disease may range from very mild (LPAI) to severe (HPAI). Accordingly, flocks of birds may show little or no sickness and death all the way up to high levels of sickness and death. Typical signs of sickness in birds that become ill from AI virus are respiratory in nature and include coughing, sneezing and nasal discharge; a drop in appetite and egg production may also be noticed. Severe forms of the disease can cause diarrhea, swelling of the face and wattles, as well as incoordination from weakness and effects on the central nervous system.2
Transmission and Spread of AI Virus
Avian influenza can be easily spread. AI virus is capable of surviving in the environment for prolonged periods of time in cool, wet conditions and almost indefinitely in frozen material. Infected birds, poultry manure, improperly processed poultry byproducts as well as equipment, people (by way of contaminated clothing, footwear, hands and hair) insects, rodents and other animals can spread the virus3.
In many cases, LPAI virus infection is identified through surveillance testing of apparently healthy birds. HPAI strains cause massive illness and deaths which would trigger a thorough investigation. Laboratory tests allow the virus and its strain to be determined. AI virus isolation and antibody testing are the primary laboratory methods used to diagnose AI infection and/or exposure to the virus. Current diagnostic methods can detect and type AI in as little as 24 hours for the HPAI strains, longer for some of the LPAI strains.
Avoiding Infection and Controlling the Spread of AI Virus
Following certain procedures can lessen the risk of infecting your birds with AI virus and reduce the risk of infecting other birds by carrying the virus out. Steps you can take to control AI include:
- Remove dirt, manure and other organic material from surfaces before applying disinfectant.
- Thoroughly clean and disinfect cages, crates, vehicles and other poultry handling and cleaning equipment with a disinfectant that will kill the avian influenza virus.
- Do not loan or borrow cages, crates, vehicles and other poultry handling and cleaning equipment.
- Only allow authorized personnel to handle birds.
- Employees and others working with the birds should use clean overalls, kept on the premise, to avoid transferring disease agents in to or out of the operation.
- Receive replacement birds only from known and reputable sources that practice good disease control practices.
- Do not travel from tne bird operation to another if at all possible. If it cannot be avoided, travel only under the strictest of sanitation measures (wash and change of clothing including footwear).
- Have sick birds properly diagnosed and disposed of if they die.
The NYS Department of Agriculture maintains an active program to identify and control avian influenza in its domestic bird population. If you have questions or would like more information about measures you can take to keep your birds free of avian influenza, speak to your poultry extension specialist or private veterinarian. Call the NYS Department of Agriculture and Markets for additional information, including a list of disinfectants that are effective in killing AI virus and other disease causing organisms on your premises.
1Wheeler KW-AVIC, USDA APHIS. Part VI Avian Influenza: 207-223.1983.
2The Merck Veterinary Manual Seventh Edition. Merck & CO., Inc.:Rahway, NJ:1991.
3USDA Veterinary Services. Fact Sheet on Avian Influenza. January 1993.
NYS Department of Health Influenza Information
U.S. Department of Agriculture (USDA) Avian Influenza site
Biosecurity for the Birds (USDA)
OIE (World Animal Health Organization) AI Updates
Centers for Disease Control and Prevention (CDC)
World Health Organization (WHO)