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
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.