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S. Tamizharasan
DPV (M) 19015 VPP
PhD Scholar
VPH 802
Department of Veterinary Pathology,
Madras Veterinary College
TANUVAS
Synonyms
 Fowl plague: Plague means “blow” in latin
 Peste aviarie: Peste means any type of deadly epidemic
disease
 Geflugelpest: in german language
 Brunswick bird plague
 Bird grippe
Intoduction
 AI is a highly contagious viral disease that affects both
domestic and wild birds.
 AI viruses have also been isolated, although less
frequently, from mammalian species, including rats,
mice, weasels, ferrets, pigs, cats, tigers, dogs and
horses, as well as from humans Zoonotic importance
 In domestic birds it ranging from asymptomatic to
peracute case
 Usually no symptoms in water fowls
Etiology
 Family: Orthomyxoviridae
 Genus: Influenza A virus
 Influenza A viruses are classified into subtypes based
on two surface proteins
 At least 16 hemagglutinins (H1 to H16), and 9
neuraminidases (N1 to N9) subtypes have been found
in viruses from birds
 AI virus strains classified into two categories according
to the severity of the disease in poultry:
Structure of an influenza A virus
 The capsid, formed by M1-
protein,
 The viral genome Negative
sense RNA virus
 The viral envelope is a lipid
bilayer formed from the
plasma membrane of the
host cell, which contains
two virus-encoded
proteins, haemagglutinin
and neuraminidase.
Inactivation
 Organic solvents : sodium deoxycholate and sodium
deoxysulfate
 Aldehydes: beta propnolactone and binary
ethylenimine
 Chemical disinfectants: Phenolus compounds, QAC,
Oxidizing agents, hydroxylamines
Classification based on
Pathogenicity
 AI virus strains are usually classified into two categories
according to the severity of the disease in poultry:
 Low pathogenic (LPAI) strains, which typically cause few
or no clinical signs in poultry, and may go undetected due
to the lack of symptoms in some species of birds.
 Highly pathogenic (HPAI) strains, which can cause
severe clinical signs and potentially high mortality rates
among poultry. IVPI (Intravenous pathogenicity factor)
greater than 1.2 or 75% mortality.
 To date, naturally occurring highly pathogenic
influenza A viruses that produce acute clinical disease
in chickens, turkeys and other birds of economic
importance have been associated only with the H5 and
H7 subtypes.
Epidemiology
 Incubation Period
The incubation period is 3 to 5 days in general but may be
longer. Maximal incubation period is 21 days
 direct or indirect contact of domestic poultry with water
birds
 Intense circulation in wild waterbirds periodical epidemic
in domestic fowl (seasonal epidemic in endemic area)
 from 2014 to 2017), several subtypes of HPAI (including
H5N1, H5N6, H5N8) have emerged in East Asia and spread
intercontinentally, stressing the crucial role of this
geographical hotspot as a source of new HPAI subtypes
Recent outbreaks (Jan 1-24 2020)
Continent Country Subtype No. of cases Human cases
Africa South Africa H5N8 2 Nil
Asia China
India
H5N1, H5N2
H5N5
24 Nil
Europe Chezh
Germany
Ukraine
Slovakia,
Hungary
Poland
H5N8 26 Nil
Avian influenza
Zoonotic importance
 Direct infection by AI virus H1N1 and H3N2 human
adapted strains sporadic
 Sustained transmission between humans never been
documented
 Only when HA, NA and basic polymerase genes from
avian gene pool have entered the human population by
reassortment leading to pandemic
 In human, H5N1 only affected 694 people and cause
402 death indicates principally it’s a pathogen of birds
 AI viruses have affinity towards alpha 2,3 linkage sialic
receptors. Human influenza viruses binds to alpha 2,6
linkage receptors
 Human lower respiratory tract also have alpha 2,3
linkage receptor which prone susceptibility
 Swine act as mixing vessel for co-infection by
influenza viruses birds and mammals with
development of new strains (reassortment)
Pandemic Influenza
 Global outbreak
 When anew flu emerges for which humans have little
or no immunity, which allows the virus to easily spread
between person to person worldwide
 3 pandemic in 20 century
 1918-19 Spanish flu
 1957-58 Asian flu
 1968-69 Honkong flu
 2009 global pandemic by H1N1
Mode of transmission
 Direct contact
 Indirect contact usually aerosol and exposure to
contaminated fomites
 Faeco-oral route
 Horizontal.
 No evidence of verticle transmission
Avian influenza
Pathogenesis
 Replicate in the intestinal and respiratory tract
 Mostly causes viremia
 Systemic spread, Hypercytokinemia
 Multifocal lymphoid necrosis, vasculitis and
thrombosis
 Necrosis and inflammation of pancreas, heart, brain,
skeletal muscles and skin
Clinical signs
 Per acute : Sudden death without prodromal symptoms
and lesions
 If survived for more than 48 hours likely in older birds
 Cessation of egg laying
 Respiratory distress
 Lacrimation and Sinusitis
 Diarrhoea and edema in head, face and neck
 Cyanosis of unfeathered skin particularly comb and wattle
 Nervous signs such as tremor of head and neck, torticolis,
inability to stand and unusual posture
Lesions
 In chicks, quails and turkeys with several day of illness
showed lesions
 Petechial hemorrhage and serous exudates in
respiratory, digestive and cardiac tissues
 Histologically characterized by vascular disturbances
leading to oedema, haemorrhages and perivascular
cuffing, especially in the myocardium, spleen, lungs,
brain and wattles. Necrotic foci are present in the
lungs, liver and kidneys. Gliosis, vascular proliferation
and neuronal degeneration may be present in the
brain.
Avian influenza
Diagnosis
 Clinical symptoms
 Primarily RT PCR assay to detect the matrix protein
(M) gene – Highly conserved and common in all
avian, mammalian influenza virus
 RT qPCR assay for specific H5 and H7 genes
 Fully sequenced to read the properties of amino acids
in the cleavage site
 Virus isolation: Cloacal swabs in wild and aquatic
birds, tracheal swabs for terrestial, domestic birds
 Inoculated through allantoic route in 10-11 day old
embryonated eggs or in MDCK cell line
 Presence of virus indicated by HA and HI test with
chicken or turkey RBCs
Serological tests
 HA and HI
 ELISA
 AGID for 16 different Haemagglutinins and 9
Neuraminidase specfic test to be done
Differential Diagnosis
 Diseases causing sudden high mortality
Newcastle disease
infectious laryngotracheitis
duck plague
acute poisonings
 Other diseases causing swelling of the combs and wattles:
acute fowl cholera and other septicaemic diseases
bacterial cellulitis of the comb and wattles
 Less severe forms of the disease may be confused with, or
complicated by, many other diseases with respiratory or
enteric signs. AI should be suspected in any disease
outbreak in poultry that persists despite the application of
preventive and therapeutic measures for other diseases.
Prevention and Control
 Depopulation
 Biosecurity
 Segregating domestic from wild and aquatic birds
 Regular surveillance with appropriate diagnostic
procedure and rapid depopulation when identified
 Education of workers
 Quarantine
 Vaccination: not recommended because surveillance
become expensive to identify infected birds in
vaccinated population

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Avian influenza

  • 1. S. Tamizharasan DPV (M) 19015 VPP PhD Scholar VPH 802 Department of Veterinary Pathology, Madras Veterinary College TANUVAS
  • 2. Synonyms  Fowl plague: Plague means “blow” in latin  Peste aviarie: Peste means any type of deadly epidemic disease  Geflugelpest: in german language  Brunswick bird plague  Bird grippe
  • 3. Intoduction  AI is a highly contagious viral disease that affects both domestic and wild birds.  AI viruses have also been isolated, although less frequently, from mammalian species, including rats, mice, weasels, ferrets, pigs, cats, tigers, dogs and horses, as well as from humans Zoonotic importance  In domestic birds it ranging from asymptomatic to peracute case  Usually no symptoms in water fowls
  • 4. Etiology  Family: Orthomyxoviridae  Genus: Influenza A virus  Influenza A viruses are classified into subtypes based on two surface proteins  At least 16 hemagglutinins (H1 to H16), and 9 neuraminidases (N1 to N9) subtypes have been found in viruses from birds  AI virus strains classified into two categories according to the severity of the disease in poultry:
  • 5. Structure of an influenza A virus  The capsid, formed by M1- protein,  The viral genome Negative sense RNA virus  The viral envelope is a lipid bilayer formed from the plasma membrane of the host cell, which contains two virus-encoded proteins, haemagglutinin and neuraminidase.
  • 6. Inactivation  Organic solvents : sodium deoxycholate and sodium deoxysulfate  Aldehydes: beta propnolactone and binary ethylenimine  Chemical disinfectants: Phenolus compounds, QAC, Oxidizing agents, hydroxylamines
  • 7. Classification based on Pathogenicity  AI virus strains are usually classified into two categories according to the severity of the disease in poultry:  Low pathogenic (LPAI) strains, which typically cause few or no clinical signs in poultry, and may go undetected due to the lack of symptoms in some species of birds.  Highly pathogenic (HPAI) strains, which can cause severe clinical signs and potentially high mortality rates among poultry. IVPI (Intravenous pathogenicity factor) greater than 1.2 or 75% mortality.  To date, naturally occurring highly pathogenic influenza A viruses that produce acute clinical disease in chickens, turkeys and other birds of economic importance have been associated only with the H5 and H7 subtypes.
  • 8. Epidemiology  Incubation Period The incubation period is 3 to 5 days in general but may be longer. Maximal incubation period is 21 days  direct or indirect contact of domestic poultry with water birds  Intense circulation in wild waterbirds periodical epidemic in domestic fowl (seasonal epidemic in endemic area)  from 2014 to 2017), several subtypes of HPAI (including H5N1, H5N6, H5N8) have emerged in East Asia and spread intercontinentally, stressing the crucial role of this geographical hotspot as a source of new HPAI subtypes
  • 9. Recent outbreaks (Jan 1-24 2020) Continent Country Subtype No. of cases Human cases Africa South Africa H5N8 2 Nil Asia China India H5N1, H5N2 H5N5 24 Nil Europe Chezh Germany Ukraine Slovakia, Hungary Poland H5N8 26 Nil
  • 11. Zoonotic importance  Direct infection by AI virus H1N1 and H3N2 human adapted strains sporadic  Sustained transmission between humans never been documented  Only when HA, NA and basic polymerase genes from avian gene pool have entered the human population by reassortment leading to pandemic  In human, H5N1 only affected 694 people and cause 402 death indicates principally it’s a pathogen of birds
  • 12.  AI viruses have affinity towards alpha 2,3 linkage sialic receptors. Human influenza viruses binds to alpha 2,6 linkage receptors  Human lower respiratory tract also have alpha 2,3 linkage receptor which prone susceptibility  Swine act as mixing vessel for co-infection by influenza viruses birds and mammals with development of new strains (reassortment)
  • 13. Pandemic Influenza  Global outbreak  When anew flu emerges for which humans have little or no immunity, which allows the virus to easily spread between person to person worldwide  3 pandemic in 20 century  1918-19 Spanish flu  1957-58 Asian flu  1968-69 Honkong flu  2009 global pandemic by H1N1
  • 14. Mode of transmission  Direct contact  Indirect contact usually aerosol and exposure to contaminated fomites  Faeco-oral route  Horizontal.  No evidence of verticle transmission
  • 16. Pathogenesis  Replicate in the intestinal and respiratory tract  Mostly causes viremia  Systemic spread, Hypercytokinemia  Multifocal lymphoid necrosis, vasculitis and thrombosis  Necrosis and inflammation of pancreas, heart, brain, skeletal muscles and skin
  • 17. Clinical signs  Per acute : Sudden death without prodromal symptoms and lesions  If survived for more than 48 hours likely in older birds  Cessation of egg laying  Respiratory distress  Lacrimation and Sinusitis  Diarrhoea and edema in head, face and neck  Cyanosis of unfeathered skin particularly comb and wattle  Nervous signs such as tremor of head and neck, torticolis, inability to stand and unusual posture
  • 18. Lesions  In chicks, quails and turkeys with several day of illness showed lesions  Petechial hemorrhage and serous exudates in respiratory, digestive and cardiac tissues  Histologically characterized by vascular disturbances leading to oedema, haemorrhages and perivascular cuffing, especially in the myocardium, spleen, lungs, brain and wattles. Necrotic foci are present in the lungs, liver and kidneys. Gliosis, vascular proliferation and neuronal degeneration may be present in the brain.
  • 20. Diagnosis  Clinical symptoms  Primarily RT PCR assay to detect the matrix protein (M) gene – Highly conserved and common in all avian, mammalian influenza virus  RT qPCR assay for specific H5 and H7 genes  Fully sequenced to read the properties of amino acids in the cleavage site
  • 21.  Virus isolation: Cloacal swabs in wild and aquatic birds, tracheal swabs for terrestial, domestic birds  Inoculated through allantoic route in 10-11 day old embryonated eggs or in MDCK cell line  Presence of virus indicated by HA and HI test with chicken or turkey RBCs
  • 22. Serological tests  HA and HI  ELISA  AGID for 16 different Haemagglutinins and 9 Neuraminidase specfic test to be done
  • 23. Differential Diagnosis  Diseases causing sudden high mortality Newcastle disease infectious laryngotracheitis duck plague acute poisonings  Other diseases causing swelling of the combs and wattles: acute fowl cholera and other septicaemic diseases bacterial cellulitis of the comb and wattles  Less severe forms of the disease may be confused with, or complicated by, many other diseases with respiratory or enteric signs. AI should be suspected in any disease outbreak in poultry that persists despite the application of preventive and therapeutic measures for other diseases.
  • 24. Prevention and Control  Depopulation  Biosecurity  Segregating domestic from wild and aquatic birds  Regular surveillance with appropriate diagnostic procedure and rapid depopulation when identified  Education of workers  Quarantine  Vaccination: not recommended because surveillance become expensive to identify infected birds in vaccinated population

Notas do Editor

  1. Low pathogenic (LPAI) strains: cause few or no clinical signs in poultry, and may go undetected due to the lack of symptoms in some species of birds. Highly pathogenic (HPAI) strains: cause severe clinical signs and potentially high mortality rates among poultry.