November 2005
From the State Vet's Office

AVIAN INFLUENZA (BIRD FLU) Is the sky really falling? PART I

by Tony Frazier

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.