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Is there
anyone who has read a newspaper, heard the news on the radio, watched the
news on TV, or spent any time on the internet in recent weeks that has not
seen or heard something about the bird flu, or Avian Influenza as it is
known in veterinary and public health circles? While Alabama presently has
no positive cases of Avian Influenza, an outbreak of Highly Pathogenic
Avian Influenza would be devastating to the United States poultry
industry, particularly in a state like Alabama that is third nationally in
broiler production.
From the
perspective of the Office of the State Veterinarian, the Alabama
Department of Agriculture and Industries and our USDA colleagues,
preventing or responding quickly to the disease in poultry is our main
focus. However, any article about the disease would not provide readers
with adequate information if the issue of the possible impact on human
health is not addressed. Therefore, in this column we will discuss the
disease along with its potential impact on human health. Next month, we
will look at the way Alabama conducts surveillance for Avian Influenza and
the Alabama Avian Influenza Response Plan.
Avian
Influenza is a contagious viral disease of many avian species including
poultry, wild and exotic birds, shore birds, and migratory waterfowl. The
highly pathogenic (pathogenic means "to cause disease") form is
characterized by severe depression, decrease in egg production, and high
death loss. The Avian Influenza virus has a wide host range and has been
isolated in 95 different species including, on rare occasions, swine and
humans. It has even been isolated from marine mammals such as whales and
seals. Infections are more common in turkeys than chickens. A primary
concern is that waterfowl tend to be reservoirs for the virus. That means
that the virus lives in these birds without causing disease.
Poultry
exist in various ecosystems such as free range (wild birds) that include
waterfowl and shorebirds, backyard and recreational poultry, live-bird
markets such as flea markets, range-raised commercial poultry, and
confined commercial poultry. One concern is the inter-mingling of birds
from some of these different ecosystems. While confined commercial poultry
operations may have biosecurity plans, wild birds are under no biosecurity
constraints.
The key
characteristics of influenza viruses are two structures on their surface
known as surface proteins. The first structure is the Hemagglutinin that
allows the virus to attach to the host (bird, pig, human, etc.) cell. The
second is the Neuraminadase that helps release virus particles from the
cell. These two structures are very important because, among other things,
they allow us to subtype the influenza virus. There are 15 different
Hemagglutinin subtypes and 9 subtypes of the Nuraminidases. The Avian
Influenza virus in Asia, and very recently found in Europe, that is
receiving so much media attention today is an H5 N1 strain.
The Avian
Influenza disease spectrum is divided into low pathogenicity and high
pathogenicity. The low path produces no disease or mild disease, and can
be any subtype. The High path produces acute severe disease and is caused
by subtypes H5 or H7 (remember we are talking about poultry). Some
clinical signs that are consistent with, although may not be, Avian
Influenza are sudden onset of illness in birds with high death loss, along
with rapid spread of the disease, and severe depression accompanied by a
drop in feed and water consumption. Some clinical signs that would
certainly warrant immediate concern are swollen heads, swollen and dark
purple or black comb and waddles and subcutaneous hemorrhage (a bruised
appearance) of the shank. Other diseases may mimic Avian Influenza, but we
cannot afford to miss this disease if it does indeed enter the United
States.
Concerning
the human health aspect of the disease, there is cause for concern, not
panic and certainly not hysteria. Your State Veterinarian and his staff
are working with the Alabama Department of Public Health on issues that
may arise should Avian Influenza (bird flu) be found in Alabama. We hear
talk about a possible pandemic, which means a large scale, worldwide
outbreak. The first reason for concern is that, although Avian Influenza
rarely crosses species to humans, this particular H5N1 virus has proven
that it can infect humans. The second reason for concern is that when this
virus has infected humans, a large percentage of those people have died.
It is worth noting, however, that only around 65 people have died from the
virus while over 100 million chickens and ducks have been disposed of due
to the disease.
Again,
remember that the human exposure was from direct contact with infected
birds. The major concern is that someone who has or is incubating the
human influenza virus could become co-infected with the highly pathogenic
Avian Influenza virus. If that situation occurs, there is the potential
for something called genetic reassortment to occur which would make the
Avian Influenza virus become easily transmissible from person-to-person.
Some medical and epidemiology experts feel that this is likely to occur,
especially since this outbreak of H5N1 Avian Influenza does not appear
that it will be contained any time soon.
As
mentioned previously, our main focus is the prevention and control of the
virus in poultry here in Alabama. For Avian Influenza, biosecurity is
where prevention and control begins and ends. Such management practices as
all-in, all-out and avoiding raising incompatible species such as ducks
and chickens on the same farm are two very important tools in the
biosecurity toolbox. Another extremely important precaution is to limit
access to poultry houses.
This is a
very important issue that all segments of society are watching. Rest
assured that Avian Influenza surveillance and a response plan if it does
occur are directly in the center of our radar screen. If you think you may
have birds with signs consistent with Avian Influenza, please contact our
office immediately at 334-240-7253. Also you can contact our regional
veterinary diagnostic laboratories, which are: Auburn Lab 334/844-4987;
Elba Lab 334/897-6340; Hanceville Lab 256/352-8036; Boaz Lab 256/593-2995.
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