Avian Influenza (with special reference to Waterfowl and notes on Hedgehogs and Bears)

Disease Summary

Alternative Names (Synonyms)

• Fowl pest
• Fowl plague
• Avian influenza A

Disease Type

Infectious/Non-Infectious Agent associated with the Disease

• Avian influenza is caused by a collection of slightly different viruses (Influenza A viruses), subtypes of which are classified mainly on the basis of haemagglutinin (H) and neuraminidase (N) antigens. There are nine recognised N subtypes and 14 recognised H subtypes (B36.22.w22)
• The virus changes rapidly by mixing of its genetic components, forming slightly different virus subtypes. Genetic reassortment readily occurs between avian influenza viruses in their natural settings. (B32.22.w7, B36.22.w22)
• Strains which remain "local" to the respiratory or digestive tract generally are of low virulence, while strains with generalise and spread through the body are of high virulence. (B13.32.w3)
• Highly pathogenic influenza A viruses, causing high mortality in domestic poultry, have to date been restricted to viruses of subtypes H5 and H7, with other subtypes producing only milder disease. (J6.33.w1)

All nine of the neuraminidase (N) subtypes and 14 of the 15 hemagglutinin (H) subtypes have been found in waterfowl, with H6 and H3 the predominant subtypes. (B36.21.w21)

Infective "Taxa"

• Orthomyxoviridae: Influenza A virus

Non-infective agents

Physical agents

References

Disease Author

Major References / Reviews

Code and Title List

Other References

Code and Title List

In Hedgehogs:
J49.45.w1

In Bears:
J1.29.w15

Detailed Clinical and Pathological Characteristics

General

• Experimental infection has been described for the hedgehog (Erinaceus europaeus - West European Hedgehog). (J49.45.w1)

Clinical Characteristics

• Very variable depending on the virus strain, host species, age and sex, concurrent disease and environmental factors. (B32.22.w7)
• May include signs of respiratory, enteric, reproductive or neurological disease. (B32.22.w7)
• Note that a given virus may produce severe disease in one species but inapparent infection on other species. (B32.22.w7)
• All except one incident of known infection in wild birds have NOT produced any clinical signs. (B32.22.w7)
• Mild signs in poultry, associated with subtypes other than H5 or H7, generally includes mild respiratory disease, depression and reduced egg production in laying hens. Disease may be more severe if other infections are also involved. (J6.33.w1)

Common signs include any or a combination of:

• General signs:
  • Decreased activity and severe depression;
  • Decreased food consumption, associated weight loss and emaciation;
  • Huddling;
  • Ruffled feathers;
  • Head and face oedema; 
    • In severe disease, the comb and wattles of poultry may show severe swelling, and there may be severe periorbital oedema.
  • Skin cyanosis; 
    • In severe disease, multifocal necrosis and haemorrhage of the comb and wattles may be noted and congestion and haemorrhage may be seen on the legs.
• Decreased egg production in laying hens, and increased broodiness;
• Respiratory signs which may be mild to severe and include coughing, sneezing, râles and excessive lacrimation;
• Nervous signs;
• Diarrhoea.

Note: Death may occur without previous development of clinical signs. (B32.22.w7)

• Usually subclinical in waterfowl. Clinical signs tend to be non-specific if they occur.
• Sinusitis, diarrhoea, increased mortality, rarely central nervous system signs occur. May see distention of infraorbital sinuses, sneezing, head-shaking, lacrimation, depression, anorexia, dyspnoea, poor condition (J3.76.w1, J3.119.w2, J6.10.w2, J28.123.w1).
  • CNS signs are considered non-specific. (B13.32.w3)
• Temporary decrease in egg production, decreased duckling growth rate, swelling and inflammation of the eyes sufficient to cause blindness, and partial paralysis just before death have been seen in some experimental infections of ducks (J1.29.w1, J5.37.w1, J21.24.w1).
• Disease lasts about three weeks. (B13.32.w30

(J18.52.w1, B12.55.w1, B13.32.w3, B36.22.w22)

• In domestic cats (Felis catus - Domestic cat)) experimentally infected with H5N1 avian influenza causing an outbreak of highly pathogenic avian influenza in domestic poultry in Asia (2003-2004) by consumption of an infected bird, or by direct transmission from an experimentally infected cat, clinical signs included (J22.306.w1):
  • Raised body temperature by one day post inoculation and remaining raised to at least seven days post inoculation.
  • Decreased activity;
  • Ocular signs (protrusion of the third eyelid, conjunctivitis)
  • Respiratory signs: laboured breathing.
  • Death in one of three cats at six days following intratracheal inoculation.

  (J22.306.w1)

• In tigers (Panthera tigris) and leopards (Panthera pardus) fed on fresh chicken carcasses during an outbreak of H5N1 highly pathogenic avian influenza in domestic poultry in Asia (2003-2004), clinical signs included:
  • High fever
  • Respiratory distress.

  (J84.10.w3)

Incubation

• Depends on viral dose, route of exposure, new host species and detection of clinical signs. (B32.22.w7)
  • A few hours to three days in an individual bird. (B32.22.w7)
  • Up to 14 days in a given infected flock. (B32.22.w7)

• In domestic cats (Felis catus - Domestic cat)) experimentally infected with H5N1 avian influenza causing an outbreak of highly pathogenic avian influenza in domestic poultry in Asia (2003-2004) by consumption of an infected bird, or by direct transmission from an experimentally infected cat, body temperature was raised by one day post infection, other clinical signs were seen by two pays post infection and low level virus excretion occurred by three days post infection. (J22.306.w1)

Mortality / Morbidity

• Both morbidity and mortality are variable depending on the virus, host species, host age and concurrent infections. (B32.22.w7)
• Usually high morbidity but low mortality. (B32.22.w7)
• Morbidity and mortality may approach 100% with highly pathogenic virus outbreaks. (B32.22.w7)

• Mortality usually zero or low in waterfowl. May be higher, even approaching 50%, in mixed infection with other viruses or bacteria (J3.76.w1, J3.119.w2, J6.10.w2).
  • Mortality may be 10 to 40% in clinical disease. (B13.32.w3)
• Nearly 30% mortality has been recorded in experimental infection (J21.24.w1).
• 29-100% reported for domestic ducklings in Hong Kong (J25.3.w1).

• One death out of three domestic cats (Felis catus - Domestic cat)) experimentally infected with H5N1 avian influenza causing an outbreak of highly pathogenic avian influenza in domestic poultry in Asia (2003-2004). (J22.306.w1)
• Infection was fatal in two tigers (Panthera tigris) and two leopards (Panthera pardus) (Felidae - Cats (Family)) fed on fresh chicken carcasses during an outbreak of H5N1 highly pathogenic avian influenza in domestic poultry in Asia (2003-2004). (J84.10.w3)

Pathology

Note: Visible lesions may be complicated by secondary bacterial involvement. (B32.22.w7)

Mild disease:

• Sinuses: inflammation, which may be catarrhal, fibrinous, serofibrinous, mucopurulent or caseous.
• Tracheal: mucosal oedema, with a serous to caseous exudate.
• Air sacs: thickened, with a fibrinous or caseous exudate.
• Peritoneum: peritonitis, egg-yolk peritonitis
• Gastrointestinal: Intestines and/or caeca may show a catarrhal to fibrinous enteritis
• Oviducts: in laying birds may be found to contain exudate.

(B32.22.w7)

Severe disease:

• Head: 
  • Oedema and swollen sinuses;
  • Wattles and combs may be cyanotic, congested and haemorrhagic.
  • Vesicles and necrosis also have been described on the comb.
• Legs:
  • Congestion and haemorrhage may be present; swelling has been described.
• Liver: necrotic foci;
• Spleen: necrotic foci; a mottled appearance was noted with one strain.
• Kidneys: necrotic foci;
• Lungs: necrotic foci;
• Gastrointestinal: petechial haemorrhage of serosal and mucosal surfaces, particularly on the proventriculus near the junction with the ventriculus. 

(B32.22.w7)

HISTOPATHOLOGY:

In classical severe "fowl plague":

• Myocardium, spleen, lungs, brain wattles (also liver and kidneys): widespread oedema, hyperaemia, haemorrhage and sometimes perivascular cuffing.
• Spleen, liver and kidney: degeneration and necrosis of the parenchyma.
• CNS (brain): necrotic foci, perivascular cuffing with lymphoid cells, glial foci, vascular proliferation, neuronal changes.

(B32.22.w7)

• Sinuses - mucogelatinous to caseous sinusitis.
• Air sacs - fibrinous airsacculitis – air sac membranes appearing cloudy and oedematous.
• Lungs - focal consolidation, particularly of the caudolateral lobes.
• Trachea: tracheitis.
• Serosal surfaces: Serositis

Histology:

• Lungs - interstitial pneumonia. Oedema, intense perivascular and diffuse infiltrates of lymphocytes, and smaller numbers of macrophages and plasma cells.
• Abdominal air sacs - multiple foci of oedema and perivascular/diffuse lymphocyte and macrophage infiltration.
• Trachea - transepithelial migration of lymphocytes .

N.B. Pathology may be due to secondary bacterial or mycoplasmal infection (Mycoplasma Infection).

(J3.76.w1, J3.119.w2, J26.26.w1, B13.46.w1, B13.32.w3, B32.22.w7, B36.22.w22)

Gross Pathology:

• In domestic cats (Felis catus - Domestic cat)) experimentally infected with H5N1 avian influenza causing an outbreak of highly pathogenic avian influenza in domestic poultry in Asia (2003-2004) by consumption of an infected bird, or by direct transmission from an experimentally infected cat, pathological findings included: (J22.306.w1):
  • Respiratory system: Pulmonary consolidation, multiple foci. (J22.306.w1)
• In tigers (Panthera tigris) and leopards (Panthera pardus) fed on fresh chicken carcasses during an outbreak of H5N1 highly pathogenic avian influenza in domestic poultry in Asia (2003-2004). (J84.10.w3)
  • Respiratory system: Severe multifocal consolidation and multifocal haemorrhage.
  • Cardiac: Multifocal haemorrhage.
  •  Hepatic: Multifocal haemorrhage in the liver.
  • Gastrointestinal tract: Stomach and intestines showed multifocal haemorrhage.
  • Thymus: Multifocal haemorrhage.
  • Lymph nodes: Multifocal haemorrhage.

  (J84.10.w3)

Histopathology:

• In domestic cats (Felis catus - Domestic cat)) experimentally infected with H5N1 avian influenza causing an outbreak of highly pathogenic avian influenza in domestic poultry in Asia (2003-2004) by consumption of an infected bird, or by direct transmission from an experimentally infected cat. (J22.306.w1):
  • Respiratory system: Diffuse alveolar damage. (J22.306.w1)
  • Virus detection: influenza virus antigen was detected in the inflamed pulmonary tissue. (J22.306.w1)
• In tigers (Panthera tigris) and leopards (Panthera pardus) fed on fresh chicken carcasses during an outbreak of H5N1 highly pathogenic avian influenza in domestic poultry in Asia (2003-2004). (J84.10.w3)
  • Respiratory system: Bronchial and alveolar epithelial loss, thickening of alveolar walls, flooding of the alveolar lumen with oedema fluid containing fibrin, rbc, neutrophils and macrophages. (J84.10.w3)
  • CNS: In one tiger and one leopard, encephalitis: multifocal infiltration of neutrophils and macrophages. (J84.10.w3)
  • Virus detection: H5N1 influenza virus was detected in the inflamed lungs using RT-PCR and was isolated from infected lung tissues by inoculation into embryonated chicken eggs. (J84.10.w3)

Gross Pathology (from experimental infection):

• Slight lesions of bronchopneumonia. (J49.45.w1)

Histology (from experimental infection):

• Liver: Congestion of capillaries, vacuolation of some liver cells, cellular infiltration (polymorphonuclear leucocytes, lymphocytes and plasma cells); occasionally an intranuclear inclusion was found. (J49.45.w1)
• Lungs: Changes of interstitial bronchopneumonia, with oedematous fluid in most alveoli, some of which were enlarged and emphysematous. Alveolar walls contained a lymphocytic infiltrate, interalveolar capillaries were congested and in some places there were small haemorrhages into alveoli. Many smaller bronchi were filled with a fibrinous exudate in which there were occasional polymorphonuclear leucocytes. (J49.45.w1)
• Central nervous system: Small inflammatory foci in the brain, consisting of lymphocytes and one or two plasma cells. Intranuclear inclusions were present. (J49.45.w1)
• No changes were found in the spleen, gastrointestinal tract, mesenteric lymph nodes or kidneys. (J49.45.w1)

Human Health Considerations

• Direct waterfowl to human virus transmission is unlikely.
• Limited replication of avian influenza viruses can occur in humans and human influenza virus can replicate in ducks and avian influenza viruses may contribute genes to human strains by genetic reassortment; virus from ducks may have been involved in the 1968 pandemic in humans.
• H1N1 viruses in turkeys, pigs and ducks may be transmitted between these species, so an avian-pig-human transmission might have human health implications.

(J20.84.w1, B32.22.w7, B36.22.w22)

• Influenza A viruses closely related to avian influenza strains have been isolated from harbour seals (Phoca vitulina - Common seal) in the USA and conjunctivitis in humans was reported in field workers and in one individual during laboratory investigations. (B32.22.w7)
• Direct transmission of influenza viruses from humans to birds does not usually occur. (B32.22.w7)
• Influenza A strains can recombine and the result may be a virulent human strain. (P24.334.w4)
• Interspecies transmission may occur between e.g. H1N1 viruses in turkeys, pigs and ducks, and there may then be public health concerns for infection of humans via the pigs. (B32.22.w7)
• During the recent (2003-2004) outbreaks of avian influenza in Asia, several case of direct transmission of H5N1 avian influenza virus to humans have occurred, and many such case have been fatal. There have also been human infections with several other avian influenza viruses in recent years, associated with illnesses ranging from conjunctivitis to influenza-like illness, and a few cases of human-to-human transmission of the avian viruses. (J6.33.w1)

Disease / Agent has been reported in either the wild or in captivity in:

• Clinical disease with mass mortality has been reported from a single incident in wild birds, in common terns in South Africa. (B32.22.w7, B36.22.w22)

In Waterfowl:

• Disease has been recorded in: domestic duck Anas platyrhynchos domesticus, and mallard Anas platyrhynchos (J3.105.w2, J3.119.w2, J25.3.w1).
• The virus has been recorded in:
• Domestic ducks in Australia, Canada, USA, Belgium, Czechoslovakia, Italy, Germany, Hungary, Israel, Poland, Ukraine, former USSR, Yugoslavia, Hong Kong (J18.52.w1).
• Coscoroba swan Coscoroba coscoroba, Ross’s goose Anser rossi, Spur-winged goose Plectropterus gambiensis gambiensis, Marbled teal Anas (Marmaronetta) angustirostris, Old world comb duck Sarkidornis melanotos melanotos, Tufted duck Aythya fuligula, Northern pintail Anas acuta at Baltimore Zoo, by serology: (J2.16.w2).
• Mallard Anas platyrhynchos, serology (J6.23.w2).
• Mallard Anas platyrhynchos, Minnesota (J5.27.w2, J1.11.w2, J4.171.w2).
• Domestic ducks and a feral mallard Anas platyrhynchos, England (J3.118.w1).
• Mallard Anas platyrhynchos, Gadwall Anas strepera, Red-crested pochard Netta rufina, common pochard Aythya ferina, Northern shoveler Anas clypeata. Serological survey, Spain (J6.23.w2).
• Mallard Anas platyrhynchos, pintail Anas acuta, Cinnamon teal Anas cyanoptera, green-winged teal Anas crecca, blue-winged teal Anas discors, ruddy duck Oxyura jamaicensis, shoveler Anas clypeata, gadwall Anas strepera, domestic duck, California (J5.18.w3).
• White Embden geese (Anser anser domesticus) (J5.19.w5)
• Whistling (Tundra) swan Cygnus columbianus, Tufted duck Aythya fuligula, Japan (J5.26.w2).
• Mallard Anas platyrhynchos, American black duck Anas rubripes, Wood duck Aix sponsa, blue-winged teal Anas discors, pintail Anas acuta, Atlantic flyway, New York state (J5.29.w2).
• Blue-winged teal Anas discors, mottled ducks Anas fulvigula, gadwall Anas strepera, green-winged teal Anas crecca, Mississippi flyway, coastal Louisiana (J5.34.w3).
• Mallard Anas platyrhynchos, American black duck Anas rubripes, blue-winged teal Anas discors, Canada geese Branta canadensis, mallard x domestic duck, Pennsylvania (J5.30.w2).
• Mallard Anas platyrhynchos, American black duck Anas rubripes, Northern pintail Anas acuta, American wigeon Anas americana, Green-winged teal Anas crecca, blue-winged teal Anas discors, northern shoveler Anas clypeata, bufflehead Bucephala albeola, Ohio (J5.35.w3).
• Mute swan Cygnus olor, and by serology Canada geese Branta canadensis, whistling swans Cygnus columbianus, Maryland (J5.36.w2).
• Mallard Anas platyrhynchos, American wigeon Anas americana, green-winged teal Anas crecca , Oklahoma (J1.16.w7).
• Mallard Anas platyrhynchos, American wigeon Anas americana, Pennsylvania (J1.31.w3).
• Canada goose Branta canadensis, in Missouri, Wisconsin, South Dakota, Michigan, Snow goose Anser caerulescens, in Missouri (J9.219.w1).
• Domestic muscovy Cairina moschata, Victoria, Australia; Pacific black duck Anas superciliosa, Western Australia (J24.71.w1).
• Mallard Anas platyrhynchos, Mississippi flyway, Minnesota (J4.171.w2).

In Hedgehogs:

• Experimental infection has been described for the hedgehog (Erinaceus europaeus - West European Hedgehog). (J49.45.w1)

In Bears:

• Antibodies to influenza A virus were detected by complement fixation (CF) test in sera from 1/22 Ursus arctos - Brown bear from Croatia (the positive individual was captive, not free-living). [1993](J1.29.w15)
• A serological survey of mammals in zoos detected antibodies to avian influenza in one of two Ursus maritimus - Polar bear (to A/Chile/1/83) and both of two Helarctos malayanus - Sun bear (to A/duck/Hung/2/77) but in neither of two Ursus arctos beringianus (Ursus arctos - Brown bear). (P5.34.w

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" volume has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• Aix sponsa - Wood duck
• Anas acuta - Northern pintail
• Anas americana - American wigeon
• Anas clypeata - Northern shoveler
• Anas crecca - Common teal
• Anas clypeata - Northern shoveler
• Anas cyanoptera - Cinnamon teal
• Anas discors - Blue-winged teal
• Anas fulvigula - Mottled duck
• Anas platyrhynchos - Mallard
• Anas platyrhynchos domesticus - Domestic duck
• Anas rubripes - American black duck
• Anas strepera - Gadwall
• Anas superciliosa - Pacific black duck
• Anser caerulescens - Snow goose
• Anser rossii - Ross's goose
• Aythya ferina - Common pochard
• Aythya fuligula - Tufted duck
• Branta canadensis - Canada goose
• Bucephala albeola - Bufflehead
• Cairina moschata - Muscovy duck
• Coscoroba coscoroba - Coscoroba swan
• Cygnus olor - Mute swan
• Cygnus columbianus - Tundra swan
• Marmaronetta angustirostris - Marbled teal
• Netta rufina - Red-crested pochard
• Oxyura jamaicensis - Ruddy duck
• Plectropterus gambensis - Spur-winged goose
• Sarkidornis melanotos - Comb duck

MAMMALS:

• Erinaceus europaeus - West European Hedgehog
• Helarctos malayanus - Sun bear
• Ursus arctos - Brown bear
• Ursus maritimus - Polar bear

(List does not contain all other species groups affected by this infectious agent)

Disease / Agent has been specifically reported in Free-ranging populations of:

• Mallard Anas platyrhynchos, Mississippi flyway, Minnesota (J1.11.w2, J4.171.w2).
• Mallard Anas platyrhynchos, American wigeon Anas americana, Pennsylvania (J1.31.w3).
• Mallard Anas platyrhynchos, American wigeon Anas americana, green-winged teal Anas crecca , Oklahoma (J1.16.w7).
• Mallard Anas platyrhynchos, England (J3.118.w1).
• Mallard Anas platyrhynchos, Northern pintail Anas acuta, Cinnamon teal Anas cyanoptera, green-winged teal Anas crecca, blue-winged teal Anas discors, ruddy duck Oxyura jamaicensis, shoveler Anas clypeata, gadwall Anas strepera, California (J5.18.w3).
• Whistling (Tundra) swan Cygnus columbianus, Tufted duck Aythya fuligula, Japan (J5.26.w2).
• Mallard Anas platyrhynchos, American black duck Anas rubripes, Wood duck Aix sponsa, blue-winged teal Anas discors, pintail Anas acuta, Atlantic flyway, New York state (J5.29.w2).
• Mallard Anas platyrhynchos, American black duck Anas rubripes, blue-winged teal Anas discors, Canada geese Branta canadensis, mallard x domestic duck, Pennsylvania (J5.30.w2).
• Blue-winged teal Anas discors, mottled ducks Anas fulvigula, gadwall Anas strepera, green-winged teal Anas crecca, Mississippi flyway, coastal Louisiana (J5.34.w3).
• Mallard Anas platyrhynchos, American black duck Anas rubripes, Northern pintail Anas acuta, American wigeon Anas americana, Green-winged teal Anas crecca, blue-winged teal Anas discors, northern shoveler Anas clypeata, bufflehead Bucephala albeola, Ohio (J5.35.w3).
• Mute swan Cygnus olor, and by serology Canada geese Branta canadensis, whistling swans Cygnus columbianus, Atlantic flyway, Maryland (J5.36.w2).
• Mallard Anas platyrhynchos , Gadwall Anas strepera , Red-crested pochard Netta rufina , Common pochard Aythya ferina, Shoveler Anas clypeata. Serological survey, Spain (J6.23.w2).
• Canada goose Branta canadensis, in Missouri, Wisconsin, South Dakota, Michigan, Snow goose Anser caerulescens, in Missouri (J9.219.w1).
• Pacific black duck Anas superciliosa, Western Australia (J24.71.w1).

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• Aix sponsa - Wood duck
• Anas acuta - Northern pintail
• Anas americana - American wigeon
• Anas clypeata - Northern shoveler
• Anas crecca - Common teal
• Anas clypeata - Northern shoveler
• Anas cyanoptera - Cinnamon teal
• Anas discors - Blue-winged teal
• Anas fulvigula - Mottled duck
• Anas platyrhynchos - Mallard
• Anas rubripes - American black duck
• Anas strepera - Gadwall
• Anas superciliosa - Pacific black duck
• Anser caerulescens - Snow goose
• Aythya ferina - Common pochard
• Aythya fuligula - Tufted duck
• Branta canadensis - Canada goose
• Bucephala albeola - Bufflehead
• Cygnus olor - Mute swan
• Cygnus columbianus - Tundra swan
• Netta rufina - Red-crested pochard
• Oxyura jamaicensis - Ruddy duck

(List does not contain all other species groups affected by this infectious agent)

General Information on Environmental Factors/Events and Seasonality

• In shorebirds: Infection is highest in September and October. (B36.22.w22)
• In pelagic birds (e.g. murres (guillemots), kittiwakes, puffins): Virus has been identified during the nesting season. It has not been possible to sample these species at other times of year. (B36.22.w22)

In Waterfowl:

• Overcrowding and stress, including the stress of transport, may encourage virus spread and clinical disease.
• Waterborne spread of virus appears important in wild waterfowl. Virus can be isolated from water; experimental data suggests virus may persist in water for several months and that persistence may be affected by temperature, pH and salinity.
• Virus isolation is highest in late summer and declines during autumn, being low in winter and spring, but the virus may be found in waterfowl all year.
• Isolation is higher in juveniles than adults, with the highest prevalence occurring at time of congregation on staging areas pre-migration, when there is also a high proportion of juveniles.
  • The virus is probably maintained by low level passage to susceptible birds throughout the year, followed by infection of high percentages (e.g. 60%) of juveniles while congregating prior to migration. (B32.22.w7)

(J1.31.w3, J5.34.w1, J5.34.w2, J5.34.w3, J5.30.w2, J5.35.w3, J5.27.w3, J18.52.w1, J19.110.w1, B12.55.w1, B13.32.w3, B32.22.w7, B36.22.w22).

Regions / Countries where the Infectious Agent or Disease has been recorded

• Disease outbreaks in domestic chickens and turkeys have occurred in Europe, the former USSR, the Middle East, the Far East, North Africa, North America and South America (B32.22.w7).
• UK, USA, Israel, Czechoslovakia, Malaysia, Belgium (J3.118.w2, J28.123.w1).
• Domestic ducks in Australia, Canada, USA, Belgium, Czechoslovakia, Italy, Germany, Hungary, Israel, Poland, Ukraine, former USSR, Yugoslavia, Hong Kong (J18.52.w1).
• Note: only 17 outbreaks of highly pathogenic avian influenza were reported worldwide form 1959 to 1998 but eight outbreaks, involving 12 countries, occurred from 1999 to March 2004; outbreaks of low pathogenicity avian influenza associated with H5 or H7 also appear to have increased in recent years. (J6.33.w1)

Regions / Countries where the Infectious Agent or Disease has been recorded in Free-ranging populations

General Information on Investigation / Diagnosis

• This disease may be suspected with peracute to acute disease, combined with gross haemorrhagic post mortem lesions. (B13.32.w3)
  • Clinical signs, being variable, can not give a definite diagnosis except during an epizootic. (B32.22.w7)
• Isolation and identification of the virus provides a definite diagnosis. (B32.22.w7)
  • Tracheal and cloacal swabs should be placed in 1-2 mL of sterile transport medium containing high levels of antibiotic. (B32.22.w7)
  • Organs can be transported in sterile plastic tubes/bags.
    • Lungs, liver, spleen and brain are the preferred organs for virus isolation. (B13.32.w3)
    • Collect and store respiratory tissues separately from intestinal tract tissues. (B32.22.w7)
  • Store samples at 4 °C for testing within 48 hours of collection, otherwise freeze at -70 °C. Storage may be carried out in liquid nitrogen or on dry ice, but storage at -20 °C (domestic freezer) is not recommended. (B32.22.w7)
• Serological testing may be used to demonstrate the presence of antibodies from as soon as seven to 10 days after infection. 
  • The HI test may be used to detect H antibodies.
  • Double-immunodiffusion may be used to detect N antibodies.
  • Virus neutralisation, CFT, single radial haemolysis, neuraminidase-inhibition and ELISA may be used in serological testing. (B32.22.w7)
  • Paired acute (as soon as possible) and convalescent (14-28 days after onset) samples should be collected and tested, with a four-fold rise in antibody titre between paired samples indicating recent infection. (B13.46.w1, B32.22.w7)
    • Sera should be stored at -20 °C, with 0.01% sodium azide as a preservative. (B13.32.w3)
• Antigen-capture ELISA, fluorescent antibody test, and monoclonal antibodies in conjunction with immunoperoxidase staining have been used for rapid detection of the virus. (B32.22.w7)
  • ELISA is very sensitive. (B13.32.w3)

• Clinical signs and pathological lesions plus virus isolation and characterization, and exclusion of other possible causes of disease.
• Cloacal swabs for virus isolation in embryonated chicken eggs. N.B. isolation is greater if cloacal swabs are used than using tracheal swabs.
• Serological testing for antibodies will indicate exposure but not present infection or carrier status. Reference antisera to all of the subtype antigen combinations are used to determine the antigenic subtype, however this does not indicate virulence.
• Virulence testing requires laboratory and animal inoculation tests, based on an index for domestic fowl.

(J4.171.w1, J6.10.w2, B12.55.w1, B36.22.w22)

• History & Documentation
• Physical Examination of Birds
• Physical Examination of Mammals
• Necropsy of Birds
• Necropsy of Mammals
• Environmental Assessment
• Chapter 2 - B36 Field Manual of Wildlife Diseases - Specimen Collection and Preservation
• Chapter 3 - B36 Field Manual of Wildlife Diseases - Specimen shipment
• Appendix A - B36 Field Manual of Wildlife Diseases - Sample specimen history form

Similar Diseases (Differential Diagnosis)

• Newcastle Disease, other paramyxovirus infections, Chlamydiosis / Psittacosis, Mycoplasma Infection and other bacterial infections must be considered. (B32.22.w7)
  • Concurrent infection with mycoplasmas or various bacteria are common. (B32.22.w7)

Specific Medical Treatment

• No specific treatment is available. (B32.22.w7)
  • Use of amantadine hydrochloride or rimantidine hydrochloride, drugs which are effective in the treatment of influenza virus infections in humans, have been shown to reduce mortality but not infection rate or virus shedding. (B32.22.w7)
  • These drugs are not licensed for use in birds for human consumption. (B32.22.w7)

• Treatment and Care - General
• Treatment and Care - Injection and Medication Techniques
• Treatment and Care - Supportive Care & Nursing

General Nursing and Surgical Techniques

• Supportive treatment to reduce respiratory distress. (B32.22.w7)
• Antibiotics against concurrent bacterial or mycoplasmal infections. (B32.22.w7)

• Treatment and Care - Supportive Care & Nursing

Preventative Measures

• Inactivated influenza virus vaccines are known to be effective in alleviating clinical signs and mortality in various species. (B32.22.w7)
• Preventative vaccination against all possible subtypes is impractical. (B32.22.w7)
• Inactivated virus of the correct antigenic subtype might be useful during an outbreak, once the subtype involved has been identified. (B32.22.w7)
• Note: regulations aiming to eradicate highly pathogenic strains may prohibit the use of vaccines. (B32.22.w7)
  • Vaccines can induce antibody production, reduce morbidity, mortality and egg-drop, but do not prevent infection and virus excretion, therefore do not eliminate the virus from the vaccinated population. (B32.22.w7)

• Preventative Medicine for Birds - General

Environmental and Population Control Measures

WATERFOWL

• Control in wild waterfowl is impractical and unnecessary.
• In commercial waterfowl, good general hygiene and management are recommended.

(J5.27.w2, J5.27.w3, B32.22.w7)

Restrict exposure of commercial waterfowl to wild waterfowl. Avoid overcrowding.

(B13.46.w1, B32.22.w7).

• Preventative Medicine for Birds - General
• Environmental and Population Management
• Chapter 4 - B36 Field Manual of Wildlife Diseases - Disease Control Operations