20 October 2022

7 minute read

By: USDA APHIS | Iowa State University

North America

Editor's Note: The following content is an excerpt from Poultry Industry Manual: The Foreign Animal Disease Preparedness and Response Plan (FAD PReP)/National Animal Health Emergency Management System (NAHEMS) Guidelines which is designed to provide a framework for dealing with an animal health emergency in the United States. Additional content from the manual will be provided as an article series.

Zone and Area Designations

The Incident Commander will work with the Operations Section and Situation Unit within the Planning Section to determine appropriate zones, areas, and premises designations in the event of an HPAI outbreak. These zones, areas, and premises designations are used in quarantine and movement control efforts. The Infected Zone immediately surrounds an Infected Premises. The Buffer Zone immediately surrounds an Infected Zone or Contact Premises. The Control Area consists of the Infected Zone and Buffer Zone. A Surveillance Zone is outside and along the border of the Control Area. A Free Area (FA) is not included in any Control Area.

The Infected Zone is frequently illustrated by a concentric circle with a radius of approximately 2 miles (3.0 km) around the Infected Premises. Similarly, the Buffer Zone is shown as a concentric circle with a radius of approximately 6.2 miles (10 km) around the infected premises. Because the Control Area includes both the Infected and Buffer Zones, the Control Area extends for a radius of 6.2 miles (10 km) around the Infected Premises. In reality, Control Areas are influenced by geography, political boundaries, and movements within the company having an infected farm(s). Criteria for issuing permits that allow movement of products within, between, or out of zones, should be in place and agreed on prior to an outbreak. As a rule, nothing moves on or off a farm with a known or suspected infected flock except what is essential for disposing of the flock and subsequent cleaning and disinfection.

People

Avian influenza viruses are highly transmissible. Movement of people among farms is the most common means by which the virus is transferred from one flock to another. Access to the Control Area is restricted to essential personnel and only necessary movement within the Control Area is allowed. Regular visits to flocks by service technicians are stopped and replaced by telephone consultations. All personnel are required to follow strict biosecurity procedures for entering and leaving premises. Disposable personal protective equipment (PPE) should be used and left on the farm. Any non-disposable items must be disinfected, double-bagged, and the outer bag disinfected prior to removal from the farm and disinfection again later in a secure area. Personnel need to shower and change clothes after leaving a farm. A record of personnel movement is kept.

Avian influenza can infect people and may even cause death. Appropriate protective gear including a respirator (N-95 or better) and goggles should be worn for one’s personal safety. People entering a positive flock need to be healthy without symptoms of possible human influenza, and they should be up-to-date on their vaccination for seasonal flu. Clinical signs of influenza in people include conjunctivitis, fever, and respiratory disease. While seasonal flu vaccination does not protect against avian influenza, it does minimize the possibility of assortment of gene segments between human and avian strains of influenza viruses. If any workers in contact with infected flocks develop symptoms consistent with influenza, they must be seen immediately by a physician and tested for influenza. Workers may be put on prophylactic antivirals, but the value of this procedure is controversial. Taking antivirals can provide a sense of false security and relaxation of personal protection.

Cancelling local and regional poultry sales and shows during a FAD outbreak is a prudent measure to prevent potential spread of the disease to other areas.

Vehicle Traffic

Vehicle access to a Control Area is restricted and includes vehicles moving all types of poultry and some types of livestock. Movement is by permit only. Control points along roads into and out of the Control Area may be needed. Vehicles are cleaned and disinfected when leaving an affected farm. Portable disinfection stations may be set up to facilitate vehicle decontamination. Particular attention should be given to the inside of vehicles (they should be either uncarpeted or have rubber flooring that can be easily disinfected), wheels, tires, and undercarriage. Routes by which vehicles travel are recorded and, if available, a GPS monitoring device is placed in each vehicle.

In the event of an H5 or H7 Low-Path AI outbreak, controlled slaughter of flocks may be permitted. Flocks should be processed as soon as possible even if they are not at the normal age. Flocks in the Control Area that are too young for processing may need to be euthanized to depopulate the area in preparation for repopulation and release of the quarantine.

Disease Monitoring

Swabs shall be collected for 5-bird pooled samples (see below) from the daily dead birds or euthanatized sick birds from each flock on each premises every other day for 14 days. Contact Premises (CP), Suspect Premises (SP), and Monitored Premises that test negative should be re-sampled as described for At-Risk Premises (ARPs). Monitored Premises may be sampled more frequently depending on the need to ship product but at the minimum must be sampled as listed above. For ARPs, swabs should be collected for 5-bird pools on each premises every 5 days for the duration of the quarantine.

Surveillance and Sampling Prior to Movement of Chickens

• A 5-bird pooled sample consists of combined samples taken from five broilers from each flock on a premises that died of natural causes during the preceding 24 hours or sick broilers that were euthanized during the preceding 24 hours. If there are less than 5 dead broilers available to create a pool, remaining samples should be taken from euthanized sick broilers.

• A flock consists of broiler chickens of the same age in one building that are marketed on the same day.

• Time to Sample Dead or Euthanized Sick Broilers Chickens. Samples must be taken within 24 hours prior to movement of live chickens (or broiler chicken products) from the premises. If an unusual HPAI virus proves to be slow-moving, adjustments to the sampling protocol will be made. For example, if broiler chickens from one farm will be marketed on four consecutive days, then samples will be collected each day for four days from all houses with birds. Targeting dead and euthanized sick birds reduces the sample size required for the 99% confidence level because the prevalence of HPAI infected birds should be higher in this group than in the house as a whole.

• Chickens Selected for Sampling. Oropharyngeal swabs must be taken only from dead or euthanized sick broilers and dead chickens should be sampled before sick chickens. Sick birds selected for euthanasia and sampling should exhibit clinical signs compatible with HPAI (depression or respiratory signs).

• Location of Sampling. Dead chickens from each house (flock) must be placed in a leak-proof container (such as a heavy-duty plastic garbage bag) each morning. Each container shall be labeled with the farm of origin, house of origin, number of birds found dead in the house that day, and the premises identification. Containers must be brought to a location near the premises designated by the Incident Command (IC).

• Sampling Procedure. An individual authorized by the IC will sample each chicken by swabbing the oropharynx of each dead chicken in the leak-proof container. One Dacron swab is used to swab the palatine (choanal) cleft on the roof of the mouth and the trachea of one chicken, picking up as much mucus as possible. Thereafter, the swab is vigorously swirled in 1.0 to 2.0 ml of Brain-Heart Infusion (BHI) broth and as much fluid as possible is squeezed out of the swab by pressing the swab on the inside of the tube before withdrawing the swab from the BHI tube. Swabs from 5 broilers should be swirled in one BHI tube.

• Disposal of Chickens after Sampling. After samples have been taken, farm personnel shall dispose of carcasses in accordance with an approved biosecurity protocol.

Sample Submission

• Laboratory Submission. BHI tubes containing oropharyngeal samples (5 oropharyngeal swabs/BHI tube) will be submitted as directed by the IC to an authorized State Veterinary Diagnostic Laboratory (VDL). These samples must be submitted on the day of sample collection by a State or Federal regulatory official or an IC- authorized person. The State VDL and IC will establish the time of day by which samples must be submitted to an authorized VDL (for example, by 12:30 p.m.).

• Laboratory Testing and Reporting. VDL personnel performing RRT-PCR will test samples immediately on receipt and electronically send test results to the IC by the end of each day. The IC will report test results to farm managers as soon as results are available. If the RRT-PCR test on the dead bird pool is not negative, additional diagnostic testing will be conducted.

• Negative RRT-PCR Results Required. Prior to movement, all the premises’ tests of 5-bird pools taken 24 hours before movement must be negative.

Reference: "USDA APHIS | FAD Prep Industry Manuals". Aphis.Usda.Gov. 2013. https://www.aphis.usda.gov/aph...

The manual was produced by the Center for Food Security and Public Health, Iowa State University of Science and Technology, College of Veterinary Medicine, in collaboration with the USDA Animal and Plant Health Inspection Service through a cooperative agreement.