High Pathogenicity Avian Influenza (HPAI)

High Pathogenicity Avian Influenza (HPAI)

• Also known as Fowl Plague and Grippe Aviaire

The Agent

• Avian influenza virus belongs to the Influenzavirus A genus.
• Avian influenza virus belongs to the Orthomyxoviridae family.
• Avian influenza viruses are classified into subtypes based on surface antigens.
• Hemagglutinin is a surface antigen with 16 types, the subtypes are designated "H".
• Neuraminidase is a surface antigen with 9 types, the subtypes are designated "N".

Pathogenicity

• HPAI causes severe disease in poultry.
• HPAI contains subtypes H5 or H7.
• Low pathogenicity avian influenza (LPAI) causes mild disease in poultry.
• LPAI contains other H subtypes, including non-HPAI H5 and H7.
• LPAI H5 or H7 subtypes can mutate into HPAI.

Reservoirs

• Waterfowl and shorebirds are influenza A natural reservoirs.
• Waterfowl and shorebirds carry all known H and N antigens.
• Influenza A is usually in the LPAI form in waterfowl and shorebirds.
• Predominant subtypes change periodically.
• Anatidae (Dabblers) are a reservoir for influenza A.

Influenza Virus Emergence

• Avian influenza virus is closely related to other influenza A viruses found in humans, horses, pigs, and dogs.
• In each species, influenza viruses typically infect only that species.

Influenza Epidemics

• A new influenza subtype must emerge in a species with little to no immunity.
• The virus must produce disease in that species.
• Sustainable transmission must occur in new species for an epidemic.

History: U.S.

• HPAI were eliminated from domesticated poultry in the U.S., but issues have arisen recently.
• Viruses can be reintroduced through imported poultry, pet birds, and wild birds.
• Rare to introduce HPAI directly; more common to introduce LPAI to domestic fowl, which then mutates to HPAI.

Geographic Distribution

• LPAI occurs worldwide in wild birds and poultry.
• HPAI has been eradicated from domestic poultry in most developed nations.
• Periodic outbreaks of HPAI occur.

Avian Influenza Zoonotic Nature

• Whether avian influenza is zoonotic depends on the specific lineage.

Morbidity and Mortality: Birds

• In domesticated poultry, HPAI morbidity and mortality rates approach 90-100%.
• Wild birds are typically asymptomatic with avian influenza.
• Some H5N1 viruses may cause death in wild birds.
• Morbidity and Mortality is host species specific and depends on recent variants of the virus*

Transmission in Wild Birds

• Influenza virus is shed in feces, saliva, and nasal secretions.
• Fecal-oral transmission is the predominant mode.
• Fecal-oral transmission involves prolonged environmental persistence.
• Other possible modes include fecal-cloacal and respiratory.

Transmission-Wild Birds

• Waterfowl-LPAI replicates in the gastrointestinal tract (GIT).
• Peak shedding occurs 2-5 days post-infection (dpi) and lasts for at least 20 dpi.
• Fecal-oral transmission occurs.
• Shorebirds are more likely to transmit via the oropharyngeal route.

Transmission Factors in Wild Birds

• Migration phenology affects influenza transmission.
• Habitat preferences influence transmission.
• Demography: Juveniles have increased shedding.
• Predisposing agents can influence transmission.
• Variants differ in environmental stability affecting transmission.

Transmission in Poultry

• Virus can spread through fecal-oral, aerosol, fomites, and mechanical vectors.
• Virus introduction include migratory birds, or infected poultry and pet birds.

Transmission in Mammals

• Close contact with dead or sick birds.
• Indirect exposure: Contact with feces and swimming in contaminated water.
• Ingestion can cause transmission.

Incubation in Animals

• Poultry: 1-7 days.
• A 21-day incubation period is used for disease control to account for virus transmission dynamics.
• Incubation period for mammals thought to be short.

Disease in Poultry

• Disease in poultry is highly virulent.
• Clinical signs include sudden death and systemic disease.
• Clinical signs include a drop in egg production and neurological signs.
• Clinical signs include depression, anorexia, ruffled feathers, swollen/cyanotic combs, conjunctivitis, and respiratory signs.
• Most birds in an affected flock die.

Disease in Wild Birds

• Disease is often subclinical in wild birds.
• Some strains cause illness in wild birds.
• Clinical signs are minimal in ducks and geese.
• Swans may be found dead.
• Experimental infections in gulls, passerines, and psittacines.

H5N1 Infections in Mammals

• In felids, fatal infections and respiratory distress can occur.
• Other mammals can be affected; cattle (recent) exhibit mild disease.
• H5N1 infections are rare in dogs and seen in palm civets.

H5N1 Infections in Swine

• Swine are susceptible to infection with all subtypes of avian influenza A
• The swine are called a "mixing vessel" so that they have receptors for both avian and human influenza viruses.
• Swine can be mild or asymptomatic.
• Mild respiratory disease and few other clinical signs are demonstrated

Communicability: Birds

• Avian influenza viruses are readily transmitted between birds.
• Viral shedding begins 1-2 days after infection.
• Viral shedding lasts up to 36 days in chickens or 72 days in turkeys.
• Birds-to-mammal transmission is uncommon.

Post Mortem Lesions: Birds

• Chickens and turkeys present with swollen sinuses and edematous combs and wattles.
• Subcutaneous edema and petechiae are present in birds.
• Trachea, lungs, and proventriculus have petechiae.

Sampling

• The proper authorities should be contacted before collecting or sending any samples.
• Only send samples under secure conditions and to authorized laboratories to prevent the spread of the disease.
• HPAI samples may be zoonotic.

Diagnosis

• Avian influenza is clinically indistinguishable from virulent Newcastle Disease (END).
• Virus isolation is key to diagnosis.
• To do viral isolation collect oropharyngeal, tracheal, and/or cloacal swabs, feces, and organ samples.
• Virology and serology are necessary for definitive diagnosis.
• Conduct AGID, ELISA, and RT-PCR for definitive diagnosis

Surveillance - Wild Birds

• Monitor the Prevalence of AIV
• Monitor Viral diversity and why is it important?
• What Causes of changes to the above?
• Maintained sample designs.
• Monitor sources vs receivers of subtypes

Alternative Samples

• Use fresh feces samples for sampling.
• Use environmental swabs samples for sampling.
• Collect feathers for samples .
• Use sentinel (domestic) ducks for sampling

Treatment

• There is no specific treatment for avian influenza.
• HPAI in poultry is usually not treated.
• Outbreaks are controlled by eradication.
• Antivirals (amantadine) are effective in reducing mortality.
• Not approved for use in food animals; results in resistant viruses.

Prevention in Poultry

• Implementing all-in/all-out flock management is key.
• Prevent contact with wild birds or their water sources.
• Do not allow birds to return to the farm from live markets.
• Practice strict hygiene and biosecurity measures.

Prevention in Poultry

• Depopulation of infected flocks.
• Implement bury, composting, and rendering for Proper carcass disposal
• Strict biosecurity measures.
• Quarantine.
• Cleaning and disinfection.

Prevention in Mammals

• Do not feed infected poultry or birds to mammals.
• Prevent contact with potentially infected flocks and wild birds.
• Keep cats and dogs indoors during avian influenza outbreaks.

Good Website for Current Information

• 2022–2024 Detections of Highly Pathogenic Avian Influenza

Exotic Newcastle Disease

• Also known as Pseudo-Fowl Pest, Pseudovogel-Pest, Atypical Geflugelpest, Pseudo-Poultry Plague, Avian Pest, Avian Distemper, Ranikhet Disease, Tetelo Disease, Korean Fowl Plague, Avian Pneumoencephalitis.

Newcastle Disease

• Newcastle Disease belongs to family Paramyxoviridae.
• Newcastle Disease belongs to genus Avulavirus.
• Newcastle disease may be lentogenic, mesogenic, velogenic, neurotropic or viscerotropic.

Newcastle Disease

• VND: virulent Newcastle Disease.
• VND includes Mesogenic, Velogenic neurotropic, Velogenic viscerotropic.
• U.S. definition for Exotic Newcastle Disease (END) includes velogenic viscerotropic strains of Newcastle.

History

• First discovered in 1926.
• First discovered in Java, Indonesia and Newcastle-upon-Tyne, England
• Probable earlier outbreaks occurred in Central Europe.
• 1896: Possibly the cause of death of all chickens in Western Scotland.
• 4 panzootics occurred from 1926 to 1981.

History in U.S.

• 1950: First U.S. case involved Partridges and pheasants imported from Hong Kong.
• 1971 to 1974: California had 1,321 infected and exposed flocks.
• 12 million birds were destroyed with and economic impact of $56 million cost to tax payers
• Additional U.S. outbreaks by Illegal importation of exotic birds, poultry

Economic Impact

• Global economic impact: VND more costly than any other animal virus?
• VND control measures are expensive.
• Repeated testing is conducted for trade purposes
• Endemic vND affects quality and quantity of dietary protein with a significant effect on human health in developing countries.

Geographic Distribution

• Newcastle Disease is Endemic in – Asia, the Middle East, Africa, Central and South America
• True geographical distribution is difficult because Vaccine use is common
• Disease is monitored by International entities/agencies of FAO and OIE

Morbidity/Mortality

• Morbidity: up to 100%
• Mortality: 90%
• Varies greatly depending on Virulence and strain, Avian species and susceptibility of host, Environmental conditions, and Vaccination history
• Some species show few or no signs – Carrier state may exist

Animal Transmission

• Direct contact with feces and respiratory secretions.
• Transmission by Indirect contact through feed, water, equipment, and human clothing.
• Transmission by Contaminated or incompletely inactivated vaccines

Animal Transmission

• Survives for long periods in the environment.
• Incubation period is from 2 to 15 days averaging 5 to 6 days.
• Migratory birds and feral pigeons contaminate of poultry feed

Human Transmission

• Presents with Mild conjunctivitis – Virus shed in ocular secretions
• Avoid contact with avian species to protect against reverse-zoonotic transmission
• Lab and poultry workers are at higher risk
• Has No cases from handling or consuming poultry products
• Has No human-to-human spread and is NOT a serious Zoonoses

Clinical Signs

• Drop in egg production.
• Numerous deaths within 24 to 48 hours.
• Deaths continue for 7 to 10 days.
• Surviving birds may have neurological or reproductive damage.

Clinical Signs

• Edema of head, especially around eyes.
• Greenish, dark watery diarrhea.
• Respiratory and neurological signs
• Signs vary with species and virulence

Post Mortem Lesions

• Edema of head and neck.
• Edema, hemorrhage, necrosis or ulceration of lymphoid tissue.
• Hemorrhagic lesions in the Tracheal mucosa, Proventriculus, and Intestinal mucosa

Sampling

• Before collecting or sending any samples, the proper authorities should be contacted.
• Samples should only be sent under secure conditions and to authorized laboratories to prevent the spread of the disease.

Laboratory Diagnosis

• Laboratory Diagnosis involves Virus isolation, RT-PCR, and Serology
• There is No strain information available when testing.
• Testing Cannot differentiate infected from vaccinated animals
• Testing May be used post-vaccination to confirm immune response

Recommended Actions

• IMMEDIATELY notify authorities beginning with Federal Area Veterinarian in Charge (AVIC) and State veterinarian
• http://www.aphis.usda.gov/animal_health/area_offices/
• http://www.usaha.org/stateanimalhelathofficials.aspx
• Quarantine premises

Recommended Actions

• Confirmatory diagnosis
• Depopulation may be necessary
• Destruction of Exposed carcasses, Litter, and Animal products

Control and Eradication

• Disinfection of premises
• Delay re-introduction of new birds for 30 days
• Control insects and rodents
• Limit human traffic

Vaccination

• Vaccination is a routine worldwide
• Reduces clinical signs
• vaccination Does not prevent virus replication or shedding
• vaccination is Not an alternative to good management, biosecurity, or good hygiene

Additional Resources

• World Organization for Animal Health (OIE) – www.oie.int
• U.S. Department of Agriculture (USDA) – www.aphis.usda.gov
• Center for Food Security and Public Health – www.cfsph.iastate.edu
• USAHA Foreign Animal Diseases (“The Gray Book”) – www.aphis.usda.gov/emergency_response/downloads/nahems/fad.pdf

This lesson covers high pathogenicity avian influenza (HPAI), also known as fowl plague. It discusses the Avian influenza virus, its classification, subtypes based on surface antigens (Hemagglutinin and Neuraminidase), and pathogenicity.