Avian Influenza

A Threat to U.S. Poultry

Worldwide, there are many strains of avian

influenza (AI) virus that can cause varying amounts

of clinical illness in poultry. AI viruses can infect

chickens, turkeys, pheasants, quail, ducks, geese,

and guinea fowl, as well as a wide variety of other

birds. Migratory waterfowl have proved to be the natural reservoir for this disease.

AI viruses can be classified into low pathogenic

(LPAI) and highly pathogenic (HPAI) forms based on

the severity of the illness they cause. Most AI virus

strains are LPAI and typically cause little or no clinical

signs in infected birds. However, some LPAI virus

strains are capable of mutating under field conditions

into HPAI viruses, which cause more illness in infected birds. The U.S. Department of Agriculture’s

(USDA) Animal and Plant Health Inspection Service

(APHIS) works to keep HPAI from becoming established in the U.S. poultry population.

AI can strike poultry quickly without any infection

warning signs. Once established, the disease can

spread rapidly from flock to flock. It is essential for

the U.S. poultry industry to be alert to this disease

threat.

Clinical Signs

Birds affected with all forms of AI may show one

or more of the following signs:

• Sudden death without clinical signs

• Lack of energy and appetite

• Decreased egg production

• Soft–shelled or misshapen eggs

• Swelling of the head, eyelids, comb, wattles, and 

hocks

• Purple discoloration of the wattles, combs, and 

legs

• Nasal discharge

• Coughing, sneezing

• Incoordination

• Diarrhea

Introduction and Spread of AI Virus

Exposure of poultry to migratory waterfowl and

the international movement of poultry, poultry equipment, and people pose risks for introducing AI into

U.S. poultry. Once introduced, the disease can be

spread from bird to bird by direct contact. AI viruses

can also be spread by manure, equipment, vehicles,

egg flats, crates, and people whose clothing or shoes

have come in contact with the virus. AI viruses can

remain viable at moderate temperatures for long periods in the environment and can survive indefinitely in

frozen material.

Biosecurity Measures on the Farm

Poultry producers should strengthen biosecurity

practices to prevent the introduction of AI into their

flocks. The following are some sound biosecurity

practices:

• Keep an “all–in, all–out” philosophy of flock

management.

• Protect poultry flocks from coming into contact 

with wild or migratory birds. Keep poultry away 

from any source of water that may have been 

contaminated by wild birds.

• Permit only essential workers and vehicles to 

enter the farm.

• Provide clean clothing and disinfection facilities 

for employees.

• Thoroughly clean and disinfect equipment and 

vehicles (including tires and undercarriage) 

entering and leaving the farm.

• Do not loan to, or borrow equipment or vehicles 

from, other farms.

• Avoid visiting other poultry farms. If you do visit 

another farm or live–bird market, change 

footwear and clothing before working with your 

own flock.

• Do not bring birds from slaughter channels, 

especially live–bird markets, back to the farm.

Report Suspicious Signs

If birds exhibit clinical signs of AI or may have

been exposed to birds with the disease, immediately

notify Federal or State animal health officials.

Additional Information

For more information about avian influenza or

biosecurity practices, contact:

USDA, APHIS, VS

Emergency Programs

4700 River Road, Unit 41

Riverdale, MD 20737–1231

Telephone (301) 734–8073

Fax (301) 734–7817

Factsheet

Veterinary Services April 2004

APHIS
The U.S. Department of Agriculture (USDA) prohibits discrimination

in all its programs and activities on the basis of race, color, national

origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to

all programs.) Persons with disabilities who require alternative

means for communication of program information (Braille, large

print, audiotape, etc.) should contact USDA’s TARGET Center at

(202) 720–2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of

Civil Rights, Room 326–W, Whitten Building, 1400 Independence

Avenue, SW, Washington, DC 20250–9410 or call (202) 720–5964

(voice and TDD). USDA is an equal opportunity provider and

employer.

United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture