Avian Influenza Frequently Asked Questions
By the University of Minnesota Extension Service - This article answers all the freqently asked questions about Bird Flu.
28 November 2005
7 minute read
What is avian influenza?
Avian influenza is a viral disease of birds.
Avian influenza virus (AIV) is maintained in a worldwide natural reservoir of wild waterfowl and shorebirds as well as in a manmade reservoir in live poultry markets.
Sometimes the virus infects commercial poultry.
The virus was first reported in North America in the 1960s.
Two pathotypes of virus are recognized: highly pathogenic viruses and mildly pathogenic viruses. Most isolates are mildly pathogenic.
There have been two major outbreaks of highly pathogenic avian influenza in the United States, one in 1924-25, reappearing in 1929, and one in 1983-84.
Mildly pathogenic outbreaks of influenza in poultry occur annually in the United States. These outbreaks are the result of the virus escaping the natural or man made reservoirs and infecting poultry.
How are influenza viruses characterized?
All avian influenza viruses are Type A.
Influenza viruses have external projections called Hemagglutinin (H) and Neuraminidase (N). There are 15 known Hemagglutinins and 9 known Neuraminidases.
Influenza viruses are subtyped by their Hs and Ns; for example, H4N8 or H1N1.
As noted above, pathotypes refer to the ability to cause disease.
Highly pathogenic influenza viruses have only been found in the H5 and H7 subtypes. This does not mean that all H5s and H7s are highly pathogenic.
How serious is avian influenza virus in poultry?
Highly pathogenic influenza virus results in high mortality in poultry flocks and the detection of highly pathogenic influenza virus causes an emergency response that usually includes killing and disposal of infected chickens and tight quarantines until it is established that the disease agent has been eliminated.
Mildly pathogenic influenza virus results in a milder disease although there may be severe disease under some conditions such as the presence of secondary bacterial infection.
Avian influenza is reportable to the Board of Animal Health in Minnesota.
Minnesota has a cooperative avian influenza control plan in place that includes education, monitoring, reporting, and a responsible response.
Flocks are routinely monitored for evidence of influenza infection. Serological tests are conducted at the University of Minnesota Poultry Testing Laboratory in Willmar.
How is avian influenza spread in poultry flocks?
Virus is excreted from the eyes, nose and mouth and in the droppings of infected birds.
Within a flock the virus may be spread from bird to bird by aerosol droplets or shared drinking water.
Transmission from flock to flock is usually by people (contaminated footwear and clothing) and equipment involved in production, live-haul or live bird marketing.
What is the public health significance of avian influenza?
Prior to 1997 there were only three known instances of avian influenza viruses being implicated in human infection. In 1959, 1979 and 1996 evidence of influenza virus was detected in humans and in each case an H7N7 was involved.
In 1997 in Hong Kong highly pathogenic H5N1 avian influenza was detected in 18 humans, 6 of whom died.
In 1999 mildly pathogenic H9N2 influenza viruses were isolated from 7 people in Hong Kong and mainland China. None died.
More recently workers in Netherlands involved in killing chickens infected with highly pathogenic influenza became infected with H7N7 and one died.
Now highly pathogenic H5N1 is circulating in poultry in several countries in the Far East and humans are being infected after coming in contact with infected poultry.
In the United States, there was one person in Virginia with an antibody titer to H7 after the 2002 H7N2 outbreak in Virginia poultry. In 2003 someone in New York became ill and the illness was confirmed by CDC to be due to H7N2 in April of 2004.
In 2004 a high path H7N3 caused mild infection in humans in British Columbia.
Are poultry workers in the United States at risk?
There has been no East Asia H5N1 influenza found in the United States
Poultry flocks in Minnesota are routinely monitored for influenza
If U.S. poultry flocks were to get infected with avian influenza, it would be a U.S. strain of virus, not an East Asia strain
U.S. poultry workers are not at risk for exposure to the East Asia H5N1 virus
U.S. poultry workers should avoid live bird markets, smuggled pet birds, backyard poultry and cock fights
What is the effect of highly pathogenic H5N1 in poultry?
This virus kills 80 to 100% of the poultry that get infected.
What is the effect of this particular highly pathogenic H5N1 in humans?
The Far East virus has infected several people resulting in fever, respiratory symptoms and reduced circulating lymphocytes. Twenty- four people died.
What is the chance that highly pathogenic H5N1 in Asia could come to Minnesota?
Avian influenza is transmitted by direct contact with infected birds and by indirect contact with contaminated people or equipment. People, clothing and equipment involved with infected poultry must be carefully cleaned and disinfected to prevent transmission of the disease.
There is little likelihood that highly pathogenic avian influenza will enter the United States because precautions are in place to control people and equipment.
All live birds entering the United States legally must undergo a period of quarantine where they are tested for Newcastle and avian influenza. No live birds are being allowed into the country from the countries affected by this outbreak.
The major risk for the importation of this virus is probably smuggled live birds, either those smuggled for the pet bird trade or for the sport of cock fighting.
What about eating chicken?
The human infections with avian influenza in the Far East, as well as all the other recorded instances of human infection with avian influenza, have resulted from contact with infected animals or droppings. Human infection has never been associated with eating poultry meat or eggs.
Human infection with avian influenza has not been associated with North or South American influenza viruses until the recent H7N3 outbreak in British Columbia.
What can people do to prevent highly pathogenic H5N1 avian influenza virus infection?
Travelers to the Far East should use caution by avoiding live poultry markets and poultry farms.
How can I help look for highly pathogenic avian influenza virus?
The first indication of highly pathogenic avian influenza in poultry is sudden deaths, often without many signs of illness. If you witness such an event contact your veterinarian or Dr Dale Lauer at the Board of Animal Health, 320-231-5170.
If you see sick game chickens or pet birds contact your veterinarian or Dr. Dale Lauer.
Contact Dr. Andre Ziegler, 612-624-1974, at the Minnesota Veterinary Diagnostic Laboratory for information on getting suspect birds examined for diagnosis.
Additional information is available from Dr. Dave Halvorson, Extension Veterinarian, at [email protected] or 612-625-5292 or
http://www.academic-server.cvm.umn.edu/outreach/AI/index.htm
17 April 2024
8
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