Highly Pathogenic Avian Influenza (HPAI) on the Poultry

Farm

Learning Objectives

• Describe normal transmission of AI

• Describe development of HPAI (vs. LPAI)

• Describe control measures– Surveillance– Enhanced biosecurity– Movement control– Destruction of contaminated birds and fomites– Role of vaccines and antivirals

Avian Influenza Overview

• Avian influenza (AI) – first isolated in 1955

• High-pathogenicity avian influenza (HPAI) – causes contagious illness, death in birds; Low-pathogenicity (LPAI) causes mild to no illness

• Vast majority of AI viruses found in birds do not represent a public health concern

Avian Influenza Overview• Virus is characterized by H and N

type (surface proteins).

• 144 possible combinations of the virus, based on 16 H types and 9 N types

• AI viruses mutate easily; only H5 and H7 viruses known to have the potential to mutate from an LPAI to an HPAI form.

• AI viruses vary widely in pathogenicity from strain to strain. Therefore not all H5N1 viruses are infectious for people or pathogenic to poultry.

HA

PB1PB2PA

NPNAMANS

M2

Hemagglutinin Neuraminidase

M1

Matrix

Species Affected

Genetic Reservoirs

Intermixing

H1, H3

H1, H2, H3H3, H7

Commercial,LBMsOthers

H1-12H14-15

H1-2, 4-7,H9-13, 15-16

H10

H1, H3, H4, H7, H13

Other AquaticBirds?

H5N1

Pathogenicity of AI

• AI strains characterized by pathogenicity in chickens

• LPAI (Low-pathogenic avian influenza)

– Mild disease in poultry– Most strains are LPAI– LPAI H5 and H7 strains can mutate into HPAI

• HPAI (Highly pathogenic avian influenza)

– Severe illness and high fatality in poultry– Some birds have no illness

Three HPAI Findings in U.S.

• 1924 – “Fowl Plague” affected live bird markets in the Northeastern U.S. Etiology was not known until 1955.

• 1983 – destruction of 17 million birds in PA and VA due to HPAI H5N2

• 2004 – HPAI H5N2 quickly contained and eradicated in TX

Development of HPAI• Low pathogenic AI strains that are most capable

of mutating into HPAI and causing epizootics– H5 and H7 – Most H5 and H7 are LPAI

• Disease– Human HPAI infection via contact with infected sick

or dead birds– Mild human LPAI infections have been documented

• Wild birds can introduce LPAI into domestic flocks– Can evolve into HPAI– Aggressive intervention required for LPAI

Signs of LPAI Influenza in Poultry

• Wild waterfowl, gulls, shorebirds are natural hosts for influenza viruses – Usually no symptoms

• Infection in non-reservoir can result in either:– No outward disease (LPAI)– Mild infection (LPAI)

• Ruffled feathers• Reduced egg production• Respiratory symptoms• Can be easy to miss!

Signs of HPAI Infection in Birds

• Causes more lethal infection – Difficult to miss - severe disease/sudden

onset– Facial edema, swollen and cyanotic combs

and wattles, drastic decline in egg production – Internal hemorrhaging of lungs and other

organs– Rapid contagion – Mortality near 100% within 48 hours

Signs of HPAI Infection in Birds

Avian Influenza in other Animals

• Domestic and wild birds – Ducks, geese, sparrows, poultry, pets

• Pigs, horses, marine mammals, ferrets, minks – Natural infection contracted from exposure to birds

• Tigers, leopards, domestic cats, dogs– H5N1 infections from ingestion of infected poultry

How is the virus spread among birds?

• Direct contact between healthy and infected birds

• Infected fecal matter• Can be found on

surface of unwashed egg shells from infected birds

Other Sources of Infection

• Fomites. Tools, equipment, and other contaminated items

• Contact with carcasses. Carcasses should be buried, incinerated, composted, or rendered

Potential Sources of Infection for Humans

• Humans

Possibly hands, hair, clothing, footwear

• Possibly contaminated equipment

• Possibly inhalation of aerosolized virus (self inoculation)

Investigators must practice biosecurity when entering / leaving a potentially contaminated farm

Measures for Prevention, Control and Eradication of HPAI in

Poultry• Increased disease surveillance in high risk

areas • Increased biosecurity on poultry farms

• Response (5 basic steps) --• Quarantine, Eradicate, Monitor the area,

Clean and Disinfect, and Test• Vaccination if necessary

Types of Poultry-Raising & Biosecurity

Sector 4

• Backyard production

• Birds/products consumed locally

9/10/2004 Cayce. Malaysia

Sector 3• Low to minimal bio-security• Birds/products enter live bird markets or other

local distribution systems

Image source: www.goodfoodkangarooisland.comFree range chickens

Sectors 1 and 2

• Sector 2– Moderate to high bio-

security– Birds/products often

marketed commercially

• Sector 1– High level bio-security– Birds/products

marketed commercially

Image source: www.fsa.usda.gov

Classification system for poultry production systems (FAO 2004)

Sector1 Sector 2 Sector 3 Sector4

System Industrial integrated

Commercial Commercial Village or backyard

BiosecuritY High Moderate to high

Low to minimal

Mimimal

Bird and product marketing

Commercial Usually commercial

Birds usually sold in live bird markets

Birds and products consumed locally

Ensure Biosecurity through Bioexclusion

• Keep poultry indoors– Separate from the outside world– Remove or disinfect all sources of infection

• Prevent unknown birds from entering flock

• Control human, vehicular, and equipment traffic onto the farm

• Use “all in – all out” production• Separate new poultry from flock• Clean and disinfect when “all out”

AI can remain viable in tissue, feces and water for a long period of time (days to weeks)

Biocontainment on Infected Farms

• Depopulation of infected and exposed birds• Movement control

– On and off farm

• Bird markets and swap meets closed and disinfected

• Testing of potentially infected birds

• Surveillance for illness in birds

Destruction and Disposal of Birds in Affected Area

• Humanely depopulate birds and other animals– Carbon dioxide– Dislocate neck– Others

• Effective disposal– Incineration– Bury– Compost– Digestion– Rendering

• Cleaning and disinfection

3/1/2006 Reuters. Karachi

Vaccination for Poultry

• Inactivated whole AI virus– Effective against H5 subtype– Reduced amount of virus in environment– May have subclinical infection

• Can still shed virus

– Administered by injection

• Vaccination may limit exportation• Recombinant vaccines under development• H5 and H7 vaccination requires USDA

approval

Antivirals

• Antivirals use only for humans

• On March 20, 2006, the FDA published a proposed final rule to prohibit the extralabel use in poultry of two classes of approved human antiviral drugs in treating influenza. FDA is taking this measure to help preserve the effectiveness of these drugs for treating or preventing influenza infections in humans.

Specifically, the order prohibits the extralabel use by veterinarians of anti-influenza adamantane (amantadine and rimantadine) and neuraminidase inhibitor (oseltamivir and zanamivir) drugs in chickens, turkeys, and ducks.

Take Home Message

• Isolate domestic birds from wild birds and waterfowl• Practice good biosecurity in all flocks• Need adequate surveillance system• Early detection and rapid response• AI response is always a joint effort

Photo: Billy Karesh, Wildlife Conservation Society

Helpful web sites• Centers for Disease Control: www.cdc.gov• World Health Organization: www.who.int/en/• World Organization for Animal Health:

www.oie.int• UN Food and Agriculture Organization:

www.fao.org• US poultry and Egg Industry Association

http://www.poultryegg.org/ • USDA Avian Influenza website

http://www.usda.gov/wps/portal/usdahome?navid=AVIAN_INFLUENZA&navtype=SU

Occupational Guidelines

Occupational Guidelines

• For persons in contact with healthy birds in HPAI-free zones– Increased vigilance and hazard

communication– Standard Personal Protective Equipment

(PPE) – Risk assessment for processing of species

that may exhibit asymptomatic disease (e.g. ducks)

Occupational Guidelines

• For persons in direct contact with known or suspected HPAI materials– Training, basic infection control, PPE to

include respirators and antiviral prophylaxis– Surveillance and monitoring of workers– Evaluation of ill persons

Occupational Guidelines

• For exposure to a known HPAI source

– Disposable particulate respirators (N-95 or greater); or powered air purifying respirator

– Current season influenza vaccine

Reduces possibility of dual infection with human and avian influenza, which could lead to reassortment

Occupational Guidelines

• For persons in contact with live or dead poultry or materials later identified as HPAI

– Medical evaluation • If symptomatic, collection of specimens for viral testing

– Post-exposure prophylaxis– Surveillance for respiratory-related symptoms

• Fever• Respiratory symptoms• Conjunctivitis