African grey world hand reared parrots
news/blog
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Wed, 02 Nov 2005
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Avian flu update.
The following is a statement of facts about the
avian flu which has been prepared by NAWA
(National Avian Welfare Alliance). It has been
written in order to help the general public have
a clearer understanding of what this avian flu is
all about. Avian Flu Captive Bird Policy -
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 Influenza viruses undergo frequent
mutations that change the pathogenicity of the
virus strains. This is called antigenic drift.
There are two categories of pathogenicity; 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. Commercial poultry flocks are maintained
in high density, high temperature and high stress
environments; when this is coupled with the close
contact these birds have with fecal and other
secretions, it allows for effortless viral
transmission and dispersal through the flock. The
poor immunity these domestic birds have towards
any disease contributes to the high mortality
rates on poultry farms. 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 a large genetic change to acquire
the ability of human to human transmission.
Larger genetic changes to a virus can happen when
an animal or human is infected with two different
strains of influenza (H5N1 mixing with H1N1 for
example). Due to the nature of viruses, genetic
information between these two strains can be
interchanged and potentially create a new strain
unique from either parent; this is referred to as
antigenic 'shift' (in contrast to
antigenic 'drift' explained above). These new
strains are what concerns health officials, in
that they can potentially lead to viral
transmission in pandemic proportions. However,
these large changes in genetic makeup are just as
likely to result in significant differences in
pathogenicity. 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
similar so disease can spread rapidly through an
infected flock. Humans can become exposed to the
virus 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. Members of clean up crews for Avian Flu
infected barns in Canada were all tested for
signs of the influenza virus, amazingly none
tested positive for the virus, even after
prolonged periods of exposure. 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 reported 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 poor 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 and
made clear 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
canceled or postponed within a county with any
positive cases of H5N1. Such events will remain
canceled 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: · Avoiding contact
with infected 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. · Owners who do not
have outside birds will be considered at lower
risk than those who have outside birds. · If
birds are housed outside other risk factors will
be considered including: o Are birds caged, with
covering over the feeding and watering areas? o
Are birds isolated from contacting potential H5N1
carriers? o Are there free-ranging poultry in the
adjacent areas? o Is there a fence that separates
the property from free-ranging poultry and other
vectors? o 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: § Sign a compliance
agreement. § Provide a biosecurity plan. §
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. § 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 in a humane
manner if test results show that they are
infected with H5N1
Posted 10:24
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