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Avian Flu Captive Bird Policy
October 25, 2005 -
Letter to NFSS Members
Background
All Influenza A viruses can infect birds. Influenza A viruses that can infect birds, but cannot easily infect humans are called Avian Flu viruses.
Influenza A viruses that have the ability to easily infect humans and can be transmitted from human to human are called Human Influenza A viruses. The
Avian Flu disease was first described in Italy in 1878, and the Avian Flu virus was first identified in 1955.
Avian Flu exists in many strains and is endemic to wild waterfowl with local rates of up to 60% positive for some waterfowl, such as mallards, but nearly
all other varieties of birds have a low rate of Avian Flu incidence. The
presence of Avian Flu in wild bird populations does not mean that the birds are diseased. Because the birds that commonly harbor these viruses have
developed resistance over many millennia, they rarely suffer illness from Avian Flu viruses. Instead, they act as the natural reservoir of Avian Flu
viruses.
Higher mortality is seen when bird species are infected with virus subtypes that are not normally found in that species of bird resulting in low
resistance levels to that virus subtype. Transmission is primarily by fecal material and also via respiratory/nasal secretions.
Most Avian Flu strains are not highly lethal, but Avian Flu viruses undergo frequent mutations that change the pathogenicity of the virus strains. There
are two categories of pathogenicty; Highly Pathogenic Avian Influenza (HPAI) and Low Pathogenic Avian Influenza (LPAI). HPAI outbreaks can cause
mortality in wild waterfowl and can also cause significant losses to domestic poultry.
Imported exotic birds (non-domesticated birds that are kept in captivity that are not native to this country) must go through USDA quarantine. During
quarantine, the birds are tested for Avian Influenza, among other diseases.
In the many years that testing has been performed on exotic birds in USDA quarantine, there has been only one isolation of Pathogenic Avian Influenza
in an exotic bird (a Pekin Robin with H7N1), ref: Dennis Senne et al. in
Avian Diseases 40:425-37(1996). The isolated strain was not pathogenic to poultry or humans. Imported and domestic exotic birds have never been a
source of HPAI infections in the United States. Exotic birds are not a
significant public health risk for Avian Influenza. Pigeons have also been shown to be resistant to Avian Influenza infection.
Influenza viruses do not persist in the environment outside of a host for long periods of time. Under ideal conditions at room temperatures, human flu
viruses can remain infective for about one week. Exposure to sunlight drastically reduces the length of time flu viruses can remain infective. For
cross infection of Avian Flu viruses to human hosts, it is likely that direct heavy exposure to an infected bird's body fluids is necessary.
Influenza viruses are classified by the types of proteins on their surface. There are 16 types of hemaglutinin (H) proteins and 9 types of neuraminidase
(N) proteins. These 2 protein types can be combined in many different ways
to create a great number of unique subtypes. Within each subtype there are also numerous strains with varying disease properties.
Influenza A viruses are H5, H7, or H9. HPAI (High pathogenic) has only occurred with H5 and H7 subtypes. H9 has only produced LPAI (Low pathogenic)
cases. Each of these 3 H-types could potentially be paired with any of the
nine N proteins to yield 27 different Influenza A subtypes, all of which can infect birds.
Currently there are only 3 recognized subtypes of Influenza A viruses that circulate in the human population. It is clear that Avian Flu viruses
rarely, if ever, jump straight to becoming Human Flu viruses. Typically, Avian Influenza must undergo a series of mutations or genetic changes to
acquire the ability of human to human transmission. Human flu strains are not able to be passed easily from bird to bird. The genetic changes
necessary for a virus to become efficient at infecting humans generally preclude it from being efficient at infecting birds. These genetic changes
also change the pathogenicity of the virus, most often resulting in a less pathogenic strain.
Avian Flu is a concern since the various strains can cause mortality and/or low production in poultry and under certain specific conditions can infect
and cause illness in humans. The most likely route of infection occurs when
free-range domestic ducks or poultry commingle with wild ducks, the natural reservoir, and then carry the virus back to domestic poultry housing where
it can spread to the rest of the poultry flock. Pathogenic forms of Avian Flu can cause significant mortality in domestic poultry since these birds do
not posses the level of resistance that wild waterfowl have to these viruses. Commercial poultry are also genetically very closely related so
disease can spread rapidly through a flock. Humans can become infected by handling infected poultry or contaminated surfaces.
Periodic outbreaks in poultry have occurred around the world, including the United States, since the disease was identified over one-hundred-twenty-five
years ago. Since 1997, for example, more than 16 outbreaks of H5 and H7
influenza have occurred in poultry within the United States. The virus strains in each of these outbreaks were just as likely as H5N1 to become
human influenza viruses, yet none of them made the jump from avian virus to human virus. Of all the people exposed to the avian flu during these 16
outbreaks, according to the CDC < http://www.cdc.gov/flu/avian/
>, only 2 mild cases of human infection in the U.S. resulted.
In 1997, transmission of Avian Influenza A H5N1 resulted in the deaths of 6 people in Hong Kong. Since then, a total of approximately 60 people have
died from H5N1. Millions of domestic birds in Asia have become infected and have been destroyed to control the spread of the virus. Although over 100
people have become infected with H5N1 in Asia, this is a very small number in comparison to the probability of numerous human exposures resulting from
husbandry practices there.
To date, all cases of H5N1 infection in humans can be traced to direct contact with infected poultry. Husbandry practices in Asia are a major
factor in its presence there. Many families keep small poultry flocks for their own consumption and for income. Poultry are allowed to roam freely,
often in yards where children play, and poultry often enter human dwellings. At the first signs of illness in poultry, the birds are frequently
slaughtered for consumption. Exposure during slaughter, de-feathering and butchering of infected birds is considered most likely to result in human
infection and this practice has been tied to a number of the human cases in Asia.
Other than certain species of ducks, all species of birds that can be infected with the H5N1 subtype of Avian Flu will exhibit high rates of
mortality and morbidity within 48 hours of infection with this virus. Exotic birds have had zero incidence of H5N1 and are not likely to become a source
of infection.
Response to H5N1
The threat to human health and to poultry production in the United States necessitates an organized plan of action to be in place prior to the
possible arrival of H5N1 here. Although H5N1 has not been found in captive birds, it may become necessary to examine or monitor captive birds for the
virus. It is important to enhance cooperation between captive bird owners and public health officials.
Media reports about H5N1 have created an unreasonably heightened state of public fear that any bird could cause Avian Flu. Any government response to
H5N1 will likely be influenced by public perception and demand. In the face
of irrational fears, a rational response is necessary to avoid further deterioration of public perception.
Culling of infected flocks is a vital means to control the spread of the virus among susceptible birds. It should be obvious that culling birds that
are not infected or that are not likely to become infected will not enhance our ability to control the spread of Avian Flu.
As long as the H5N1 virus does not gain the ability to transmit from human to human, its impact on human health will continue to be minimal. However,
it is important to eliminate the virus from the avian population to protect
both birds and people. In the unlikely event that this virus gains the ability for human to human transmission, it must be recognized that culling
birds will no longer have an impact on controlling the spread of the virus. If the virus arrives in the United States in a state that allows it to
spread directly from human to human, any government response that includes culling of birds will only drain vital resources away from vital human
health services.
Because imports of most exotic birds were halted in 1992 under the Wild Bird Conservation Act, much of the breeding stock available to aviculturists is
irreplaceable. Many of these birds are endangered in their native habitats
and the captive birds may represent a valuable genetic resource for the survival of that species. To prevent unnecessary culling of valuable and
irreplaceable birds, the following policy is formulated to establish guidelines to protect captive bird facilities and pet bird owners, yet allow
for appropriate measures should H5N1 arrive in the United States.
H5N1 Avian Flu Captive Bird Policy
Part 1 (Human H5N1)
If H5N1 arrives in the United States in a form that can be transmitted from human to human, culling of captive birds to control H5N1 will have no impact
on the spread of the virus. Under this scenario, H5N1 is a human health issue that is not affected by birds. Therefore, culling of captive birds to
control Human H5N1 shall not occur.
Part 2 (Avian H5N1)
Bird Marts and Bird Exhibitions, where live birds are brought together from separate facilities, will be cancelled or postponed within a county with any
positive cases of H5N1. Such events will remain cancelled or postponed until
such time as the county remains H5N1 free for 30 days.
An Avian H5N1 eradication program includes surveillance for infected birds and euthanasia of all birds testing positive for Avian H5N1. Typically all
birds on a premise will be destroyed if any bird on that premise tests positive for H5N1. Exceptions to this policy are outlined below.
Captive birds housed in cages within enclosed structures or housed in outdoor caging under specified conditions should be exempted from euthanasia
according to the following policy.
Birds qualified for exemption from euthanasia include:
A. All birds greater than 500 meters from any H5N1 positive.
B. Endangered species (protected under the U.S. Endangered Species Act)
assessed in conjunction with the U.S. Fish and Wildlife Service, which is
authorized to quarantine, seize, or destroy endangered species.
C. Rare and/or threatened species as listed in the CITES Appendices, I, II
or III.
D. Genetically significant species or strains of captive or domestic avian
species.
E. Captive birds with an effective biosecurity program that protects them
from H5N1. An appropriate biosecurity program includes:
F. Avoiding contact with affected birds; isolating birds from loose birds
in the neighborhood; preventing people from spreading the disease on
contaminated clothing, shoes, and vehicles; and cleaning and disinfecting
all equipment and supplies in contact with affected birds.
G. Owners who do not have outside birds will be considered at lower
risk than those who have outside birds.
H. If birds are housed outside other risk factors will be considered
including:
I. Are birds caged, with covering over the feeding and watering areas?
J. Are birds isolated from contacting potential H5N1 carriers?
K. Are there free-ranging poultry in the neighborhood?
L. Is there a fence that separates the property from free-ranging
poultry and other vectors?
M. Birds included in categories A-D will be evaluated and quarantined
on the premises, or taken to a USDA quarantine station. Only birds that test
positive for H5N1 will be euthanized. Any birds exempted from euthanasia
will be tested, examined, and isolated. Isolation facilities must provide
secure bio-containment against H5N1. If the bird is quarantined the
owner/operator must:
N. Sign a compliance agreement.
O. Provide a biosecurity plan.
P. Allow samples to be taken by a state or federal animal health
official for virus isolation. A minimum of two consecutive negative samples
at least 7 days apart are required.
Q. Agree to additional guidelines for determining when the quarantine
can be removed as discussed at the time the compliance agreement is signed.
The quarantine will remain in place for a minimum of 14 days. The quarantine
will not be lifted until surveillance has been completed in the neighborhood
around the quarantined premises (in an approximately 1-kilometer zone) and
until there are no infected premises within that 1-kilometer zone around the
quarantined premises. Individual birds will be euthanized if test results
show that they are infected with H5N1.
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