A brief overview of zoonotic risk due to Avian influenza virus. Pandemic influenza virus has its origins in avian influenza viruses. The highly pathogenic avian influenza virus subtype H5N1 is already panzootic in poultry, with attendant economic consequences. It continues to cross species barriers to infect humans and other mammals, often with fatal outcomes. Therefore, H5N1 virus has rightly received attention as a potential pandemic threat. However, it is noted that the pandemics of 1957 and 1968 did not arise from highly pathogenic influenza viruses, and the next pandemic may well arise from a low-pathogenicity virus. The rationale for particular concern about an H5N1 pandemic is not its inevitability but its potential severity. H5N1 pandemic is an event of low probability but one of high human health impact and poses a predicament for public health. Here, we review the ecology and evolution of highly pathogenic avian influenza H5N1 viruses, assess the pandemic risk, and address aspects of human H5N1 disease in relation to its epidemiology, clinical presentation, pathogenesis, diagnosis, and management.

1. AVIAN INFLUENZA
SUBMITTED BY:
SUBMITTED TO:
Dr MOHAN SINGH VIVEK KUMAR
MVSc 1st Year
(Veterinary Pathology Dept)
PGS 502
TECHNICAL WRITING &
COMMUNICATION SKILLS

2. INTRODUCTION
• Avian influenza, known informally as avian
flu or bird flu, is a variety of influenza caused
by viruses adapted to birds .Avian influenza is a
viral infection found in domestic poultry & a wide
range of other birds.
• AI viruses are typically of low pathogenicity ,causing
subclinical infections, respiratory disease ,drops in
egg production, few AI viruses are highly
pathogenic causing severe systemic disease with
multiple organ failure & high mortality.

3. ETIOLOGY
• Avian influenza viruses are type A Orthomyxoviruses
(Influenzavirus A)
• Avian influenza viruses are further divided into 16
Hemagglutinin (H 1-16) & Neuraminidase (N1-9)
subtypes.
• Shows phenomenon of Antigenic shift (mutation &
recombination) & Antigenic drift(point mutations).
• Avian influenza A viruses are classified into the
following two categories:
• Low pathogenic avian influenza (LPAI) A viruses
• Highly pathogenic avian influenza (HPAI) A viruses.

4. Various Subtypes of Influenza Virus
Pigs have been regarded as being a possible intermediate host
(“mixing vessel”)

5. STRUCTURE
• Enveloped ,single-stranded RNA viruses with
helical nucleocapsids & spherical or pleomorphic
morphology.
• “Replicates in Nucleus”

6. COMPARISON
HPAI
• Infection of poultry with HPAI
viruses can cause severe disease
with high mortality.
• The HPAI viruses arise from
mutation of some H5 and H7
LPAI viruses.
• Both HPAI and LPAI viruses can
spread rapidly through poultry
flocks. However, some ducks can
be infected without any signs of
illness.
LPAI
• Infection of poultry with LPAI
viruses may cause no disease or
mild illness (such as ruffled
feathers and a drop in egg
production) and may not be
detected.
• LP viruses are recovered from
imported pet birds and ratites. The
viruses may be present in village
or backyard flocks.
• Avian influenza A viruses have
been isolated from more than 100
different species of wild birds.
Most of these viruses have been
LPAI viruses.

7. Epidemiology and Transmission
• The HPAI viruses arise from mutation of some H5 and
H7 LPAI viruses and cause devastating epidemics.
• Stamping-out programs are used to quickly eliminate
the HPAI viruses in developed countries, but some
developing countries may use vaccines and
management strategies to control HPAI viruses.
• The incubation period is highly variable and ranges
from a few days in individual birds to 2 weeks in the
flock. Transmission between individual birds is by
ingestion or inhalation.
• Airborne dissemination between farms may be
important over limited distances.

8. • Sporadic natural and/or experimental infections
have occurred in cats and dogs with H5 Eurasian
HPAI viruses.
• Other mammals have been experimentally infected
with H5 HPAI viruses, including pigs, ferrets, rats,
rabbits, guinea pigs, mice, mink, and nonhuman
primates.
• In certain geographic areas, dogs (H3N8 and H3N2)
and cats (H7N2) may be commonly infected by
specific influenza A viruses that are adapted to each
specific species.

9. Clinical Findings and Lesions
• Most avian influenza viruses (H1-16 subtypes) are LPAI,
but some of the H5 and H7 AI viruses are HPAI and
highly lethal for chickens, turkeys, and related
gallinaceous domestic poultry. This HPAI form of the
disease has historically been called fowl plague. In
most wild birds, AI viral infections are subclinical except
for the recent H5 HPAI viruses of Eurasian lineage,
which have been associated with mortality in wild
and/or domestic waterfowl and other species of wild
and domestic birds. Clinical signs, severity of disease,
and mortality rates vary, depending on AI virus strain
and host species

10. Low Pathogenicity Avian Influenza Viruses
• Low pathogenicity avian influenza viruses typically
produce respiratory signs such as sneezing,
coughing, ocular and nasal discharge, and swollen
infraorbital sinuses in poultry. Sinusitis is common
in domestic ducks, quail, and turkeys.
• Lesions in the respiratory tract typically include
congestion and inflammation of the trachea and
lungs.
• In layers and breeders, there may be decreased egg
production or infertility,

11. High Pathogenicity Avian Influenza Viruses
• Even in the absence of secondary pathogens, HPAI
viruses cause severe, systemic disease with high
mortality in chickens, turkeys, mortality can be as high
as 100% in a few days.
• In peracute cases, clinical signs or gross lesions may be
lacking before death. However, in acute cases, lesions
may include cyanosis and edema of the head, comb,
wattle, and snood (turkey); ischemic necrosis of comb,
wattles, or snood; edema and red discoloration of the
shanks and feet due to subcutaneous ecchymotic
hemorrhages; petechial hemorrhages on visceral
organs and in muscles; and blood-tinged oral and nasal
discharges. In severely affected birds, greenish diarrhea
is common.

12. Avian influenza, subcutaneous
hemorrhage of the skin on feet
(Hemorrhagic skin visible on the feet of a chicken with avian influenza)

13. Avian influenza, ischemic necrosis of comb and wattles, chicken
Hemorrhagic skin visible on the unfeathered head
regions of a chicken with avian influenza.

14. Diagnosis
• Avian influenza virus isolation
• Detection of AI viral RNA
• Detection of AI-specific antibodies
The presence of clinical disease alone is not
diagnostic. Low pathogenicity and high pathogenicity
avian influenza viruses can be readily isolated from
oropharyngeal and cloacal swabs, and HPAI viruses
from many internal organs. AI viruses grow well in
the allantoic sac of 9- to 11-day-old embryonating
chicken eggs, and they agglutinate RBCs. Such
hemagglutination is not inhibited by Newcastle
disease or other paramyxoviral antiserum

15. AI viruses are identified by demonstrating the
presence of:
• Influenza A matrix or nucleoprotein antigens using
AGID or other suitable immunoassays
• Viral RNA using influenza A-specific reverse
transcriptase PCR
• Reaction with antibodies specific for AI virus
• AI viruses are further classified into hemagglutinin
(H1-16) and neuraminidase (N1-9) subtypes based
on the hemagglutinin inhibition and neuraminidase
inhibition tests.

16. Differential Diagnosis
• LPAI must be differentiated from other respiratory diseases or
causes of decreased egg production, including:
• acute to subacute viral diseases such as infectious bronchitis,
infectious laryngotracheitis, low virulent Newcastle disease,
and infections by other paramyxoviruses
• bacterial diseases such as mycoplasmosis, infectious coryza,
ornithobacteriosis, turkey coryza, and the respiratory form
of fowl cholera
• fungal diseases such as aspergillosis
• HPAI must be differentiated from other causes of high
mortality such as virulent Newcastle disease, the peracute
septicemic form of fowl cholera, heat exhaustion, and severe
water deprivation

17. Prevention and Treatment
• preventive measures
• supportive care
• preventive measures: Suspected outbreaks should be
reported to appropriate regulatory authorities.
Antigenically matched and properly administered
vaccines can prevent clinical signs and death and
greatly reduce virus replication and shedding from the
respiratory and GI tracts.
• Supportive Care: Treating LPAI-affected flocks with
broad-spectrum antibiotics to control secondary
pathogens and increasing house temperatures may
reduce morbidity and mortality. Treatment with
antiviral compounds is not recommended.

18. VACCINATION
• The following vaccine types are currently available
• Inactivated vaccines ƒ
:
• Monovalent including either H5 or H7strains
• ƒBivalent including H5 and H7 strains ƒ
• Both monovalent and bivalent vaccines can contain
homologous or heterologous neuraminidase subtype.
• Live recombinant vaccines: (fowlpox H5): these are
efficacious only in chicken species, and then only in
day-old chicks as exposure in later life to wild-type fowl
pox virus would preclude the use of the vectored
vaccine.

19. ZOONOTIC RISK
• Avian influenza viruses exhibit host adaptation to birds.
Human infections have occurred, usually as isolated,
rare, individual cases. Most human cases have
originated from infection with Eurasian H5 HPAI virus
(A/Goose/Guangdong lineage), and, most recently,
H7N9 LPAI virus (Eurasian lineage). This lineage of
H5N1 HPAI virus has total accumulated human cases in
Asia and Africa from 2003–July 2020 of 861, of which
455 were fatal.
• The primary risk factor for human infection has been
direct contact with live or dead infected poultry, but a
few cases have resulted from consumption of uncooked
poultry products, defeathering of infected wild swans,
or close contact with human cases.

20. • Respiratory infection has been the most frequent
presentation of human H5 cases. This virus has
very limited human-to-human transmission. For
H7N9 LPAI, total accumulated human cases in China
since 2013 is 1,568, of which 616 were fatal..
• Conjunctivitis was the most frequent symptom in
human cases of H7N7 HPAI virus infection in the
Netherlands during 2003, with 89 confirmed cases
and 1 fatality. Other HPAI viruses and all LPAI viruses
have produced very rare or no human infections.

21. OUTBREAK
• Bird Flu in India :Bird flu, also called Avian flu, Avian
influenza viruses infect birds, including chickens, other
poultry and wild birds such as ducks. Most bird flu viruses can
only infect other birds. However, bird flu can pose health risks
to people. The first case of a bird flu virus infecting a person
directly, H5N1, was in Hong Kong in 1997. Since then, the bird
flu virus has spread to birds in countries in Asia, Africa and
Europe.
• Deadly H5N1 strain hit India in January. More than 3.9
million chickens and ducks were culled to prevent the spread
of the virus across the country, Food and Agriculture
Organisations said in a statement on Wednesday. No new
disease outbreaks have been discovered since Feb. 2, 2008,
FAO said. Avian influenza hits mostly birds but its H5N1 strain
has killed 234 people since 2003 when it began in Asia,
according to the World Health Organisation (WHO).

22. 2020–21 H5N8 outbreak
• In 2020 and 2021, an ongoing outbreak of Avian
influenza subtype H5N8 has been occurring
at poultry farms and among wild bird populations in
several countries and continents, leading to the
subsequent cullings of millions of birds to prevent a
pandemic similar to that of the H5N1 outbreak in
2008.

23. OUTBREAK IN INDIA
• The Union Ministry of Fisheries and Animal Husbandry
have asked other states to keep a vigil on any unusual
mortality amongst birds. The current bird flu outbreak
comes few months after India on September 30, 2020,
declared the country free from the disease. India
notified the first outbreak of Avian Influenza in 2006.
• Kerala declares Bird flu as state disaster
• The Kerala government classified the avian flu outbreak
as “state disaster” after the Centre notified the
outbreak of H5N8 subset of Influenza A in two districts
of Kottayam and Alappuzha. Culling of nearly 50,000
birds is currently in progress in the two districts.

24. Health workers in protective suits prepare to set fire after culling ducks following the
detection of H5N8 strain of bird flu among domestic birds in Alappuzha district, Kerala.
Avian Influenza, or the bird flu outbreak, had so far been reported at 12 epicentres across
four states — Kerala, Rajasthan, Madhya Pradesh and Himachal Pradesh — and issued
advisories to contain further spread of the infection.
Of the 12 epicenters, the bird flu has been reported in crows in Baran, Kota, Jhalawar
region of Rajasthan as well as Mandsaur, Indore, Malwa areas of Madhya Pradesh. In
Himachal Pradesh, the infection was found in migratory birds in Kangra region and in
poultry ducks in Kottayam, Alappuzha (4 epicentres) in Kerala.

25. MP,RAJASTHAN
• Presence of H5N8 virus (a variant of avian influenza
or bird flu) was found in the carcasses of crows in
Mandsaur and Agar Malwa district, PTI reported,
citing government officials. A total of 155 dead
crows in Indore have been found with the H5N8
virus since the pathogen was first detected in the
state’s commercial hub a week back.
• the number of birds found dead in the state in
recent weeks has crossed 600. The fatalities were
reported in 16 of the 33 districts of Rajasthan

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