Know more about 'Avian
Avian influenza, also known as ‘fowl plague’,
is an infectious disease of birds caused by type A strains of the influenza
The disease, which was first identified in
Italy more than 100 years ago, occurs worldwide in many domestic birds,
including chicken, turkey, ducks etc.
In the wake of Avian influenza ( AI )
spreading in Asian countries, the latest reports from neighbouring country
Pakistan has put India on red alert
The high mutation rate of low
pathogenic influenza virus can result in the generation of extreme virulent
forms with high propensity for inter species transmission. This was
highlighted by the recent human casualties in Thailand and Vietnam.
It is highly
imperative that some concrete measures be taken at national level to prevent
a major catastrophe and we
veterinarian's have a vital
role to play.
Some Important Facts about
The etiological agent
belongs to the Influenza virus A genus of Orthomyxoviridae family
and are negative stranded segmented RNA virus.
The influenza A virus can
be divided into 15 subtypes on the basis of haemagglutinin (H) antigens
. Neuraminidase is the other type of antigen present (9 in No.). All
H and N combinations have been isolated from birds.
have proved to be the natural reservoir for this disease which
are more resistant to avian influenza than
Among domestic poultry
species, turkeys are more commonly infected than are chickens.
Influenza, as a disease is classified into 2 categories viz
Highly Pathogenic Avian
Influenza (HPAI) which
causes high mortality and Low pathogenic Avian Influenza (LPAI)
which is less severe.
of haemagglutinin antigen, requires post translational cleavage by
host proteases before it becomes functional and infectious.The
presence of multiple basic amino acids at the cleavage site of HA0 molecule
in HPAI enables the virus to replicate throughout the body, damaging
vital organs which results in disease and death.
LPAI viruses on the other hand have only
two basic amino acids in the cleavage site motif enabling
them to replicate in only limited tissues and organs
and antigenic drifts are very common in AI virus which can
lead to production of HPAI from LPAI types.
control of LPAI is also very important.
Transmission of disease between avian species :
direct and indirect contact; contact with wild birds are often incriminated
as a source.
evidence of vertical transmission in birds but
viruses have been isolated from the outer shell of eggs.
Important clinical signs in birds:
Nasal discharge, sneezing and diarrhea;
Swelling of head, wattle, eyelids, combs and hocks
Transmission to humans:
has been reports that H5N1 strain of AI virus to
infect humans during the 1997 outbreaks in Hong
Kong and the recent outbreak in Vietnam.
In 1997 outbreak, 6 out of 18 infected people died
and 16 deaths have been registered in recent pestilence as on 5th
LINK? Although very rarely avian and human virus
go for genetic reassortment, a mixing vessel is required for
evolution of more virulent viruses. Pigs were identified as this
missing link in 1993-94 and it therefore underscores the impact of disease in India than in Pakistan.
Till now it
is not very clear regarding the HUMAN to HUMAN transmission of disease,
although W.H.O has indicated its possibilities.
Symptoms of H5N1 in
humans are very similar to other influenza viruses, typically with fever,
malaise, myalgia, sore throat and cough.Conjunctivitis is
also noticed in some cases.
destruction and disposal of infected and exposed birds.
An alarming situation for poultry industry.
Strict quarantine and
Total ban on marketing of slaughter
birds from infected farms must be enforced.
Decontamination to remove
and reduce the virus.
One gram of chicken manure can contain enough
viral particles to infect one million birds with AI
to estimate the spread of disease.
programme should be implemented using inactivated homologous or heterologous
Capua I and Marangon S (2000). The avian
influenza epidemic in Italy, 1999-2000: a review. Avian Pathol. 29:
Capua I and Marangon S (2003). The use of
vaccination as an option for the control of avian influenza. Avian Pathol.
Claas E C J, Kawaoka Y, De Jong J C, Masurel
N, and Webster R G (1994). Infection of children with avian human
reassortant influenza virus from pigs in Europe. Virology. 193:
Claas E C J (2000). Pandemic influenza is a
zoonosis, as it requires introduction of avian-like gene segments in the
human population. Vet. Microbiol. 74: 133-139.