Avian influenza is a zoonotic and notifiable disease which occurs world wide. Different risk factors are associated with transmission of the disease to humans. It has two forms HPAI and LPAI. The disease has an impact on public health and economics of the country. In Malawi,it seems the disease appeared in 2005 where it attacked migratory birds

1. shareefngunguni@gmail.com
Class work, unpublished
AVIAN INFLUENZA IN HERD HEALTH
AND PRODUCTION ECONOMICS
Authored By:
LUANAR,2018
Shareef Ngunguni, BVM

2. INTRODUCTION
Avian influenza is a notifiable disease
of poultry caused by any influenza virus
of the H5 or H7 subtypes or by any
avian Influenza virus with an
Intravenous Pathogenicity Index (IVPI)
of greater than 1( at least 75%
mortality) Pattison et al, (2008).Avian
Influenza viruses are grouped into High
Pathogenic Avian Influenza (HPAI) and
Low Pathogenic Avian Influenza (LPAI).
High Pathogenic Avian Influenza
viruses cause at least 75% mortality in
4-6 week old chickens infected
intravenously and these viruses have
an Intravenous Pathogenic Index of
greater than 2. HPAI virus with
Intravenous Pathogenicity Index of less
than 1.2 cause less than 75%
mortality. Low pathogenic Avian
Influenza causes mild respiratory
infection and it is common in many
countries and in species other than
domestic fowl and turkey (Gordon,
1977). Avian influenza is one of
Infectious animal diseases that causes
major losses to livestock production;
also a major cause of poor animal
welfare. Within livestock production, it
is too late to undertake actions only
after clinical signs of disease have
developed. Instead, a continuous focus
on disease prevention is needed.
DISSCUSION
Species affected
Avian influenza virus A has been
isolated from
chickens,turkeys,ducks,various wild
birds,quals,pheasants,patridge and
tern,and probably all avian species are
susceptible. However pigeons are
resistant (Gordon, 1977).In December
2005, migratory birds dropped dead in
Ntchisi and suspected to be due to the
disease.
Epidemiology
The disease is worldwide distributed
but it is common in Asia, west and
North Africa. There was an incident in
Ntchisi, central region of the country in
December 2005, where thousands of
sick migratory birds (fork-tailed
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AVIAN INFLUENZA IN HERD HEALTH
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drongos) dropped dead from the sky,
precipitating fear of an avian flu
outbreak in the country. Wild birds
serve as reservoirs and transmit
infection to subsistence flocks or
commercial units which are operated
with substandard biosecurity. Seasonal
migration of wild birds is the major viral
spreading risk factor. The virus can be
transmitted directly or indirectly.
Indirect infection can occur by moving
flocks, equipment and personnel and
by wind dispersal of virus-laden dust
and feathers. Direct infection occurs
following contact between infected
carriers and susceptible flocks. High
Pathogenic Avian Influenza virus is
resistant to environmental exposure
and affect all poultry operations in a
region unless appropriate controls are
implemented (Shane, 2005).
Risk Factors
The primary risk factor for human
infection appears to be direct or
indirect exposure to infected live or
dead poultry or contaminated
environments, such as live bird
markets. Slaughtering, defeathering,
handling carcasses of infected poultry,
preparing poultry for consumption,
especially in household settings, are
also likely to be risk factors. Some
common neglected factors include
association with birds, poultry farms
and bird fresh feaces. The large
wetlands around the Lake of Malawi
provide a high risk of HPAI, creating an
ideal breeding ground for the avian
virus in seasonal migratory birds.
Diagnosis
Clinical signs vary, depending on the
pathogenicity of Avian influenza virus
and other factors as host species, sex,
concurrent infections, acquired
immunity and environmental factors
(Shane, 2005). Low Pathogenic Avian
Influenza shows generally mild
symptoms: respiratory coughing
sneezing, wet eyes, nasal discharge
depression, lethargy limited reduction
of feed intake and limited drop in egg
production; low mortality rate. High
Pathogenic Avian Influenza shows fast
onset with increased mortality even
before clinical signs are seen,

4. depression, drop in feed and water
intake, severe drop in egg production
and mortality can vary between 50-
90% Pattison et al, (2008).
The above clinical signs are indicative
of Avian Influenza (tentative diagnosis)
but definitive diagnosis is done by
laboratory tests such as
· Polymerase Chain Reaction to
detect the virus proteins or
Nucleic Acid(RNA)
· Isolation of the virus from
infected organs, tracheal and
Cloacal swabs
· Serology tests to detect Avian
Influenza antibodies in blood
samples
It seems Malawi doesn’t have the
privilege to diagnose the disease since
it lack facilities and equipment used for
diagnosis. For example, samples were
sent to Republic of South Africa to
diagnose if it was Avian Influenza which
caused thousands of sick migratory
birds (fork-tailed drongos) to drop dead
from the sky in Ntchisi December,
2005.
Control and Preventions
Infected flock are slaughtered and
disposed of; this is followed after blood
testing or virus isolation from the flock
to diagnose which birds are positive/
infected. In countries such as USA
producers are compensated half of
their loss after infected birds are
euthanized. There is also a waiting
period of 7 days which includes
cleaning and disinfecting facilities
before repopulation with birds following
depopulation (Scanes et al, 2004).
Suspected flocks are quarantined to
identify flocks demonstrating
antibodies to Avian Influenza.
Studies have shown that strict
biosecurity measures limit
dissemination of avian influenza virus
among commercial farms and within
integrations (Shane, 2005). Preventing
the spread of virus is extremely difficult
in the context of industries in
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AVIAN INFLUENZA IN HERD HEALTH AND
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Document Title
developing countries such as Malawi
where feed is delivered in bags; eggs,
culled hens and live broilers produced
by small-scale farmers are distributed
through a network of dealers to
regional markets.
Health birds needs to be vaccinated or
immunized with autogenous
inactivated vaccine or a recombinant
vector product (Shane, 2005). The
disadvantage of Vaccination is that it
suppresses clinical occurrence of
disease but the virus persists in the
poultry population of the affected
region, hence inhibits exports
(Sainsbury, 1992). Vaccination is
generally done with inactivated AI
vaccines based on the strain H-type
causing the outbreaks.
When an outbreak occurs in a region,
movement of flocks and products from
foci of infection to other areas should
be restricted to prevent disseminating
the virus into free infected areas.
Treatment
There is no useful treatment other than
supportive antibiotics and vitamins
administration (Sainsbury, 1992).The
antibiotics are used to control
secondary bacterial infections
Public Health significance.
Outbreaks of avian influenza has
impact on economy of poultry
producers. Examples of economic
consequences of the outbreak include
reduction of poultry consumption by
consumers, and increased additional
cost for implementing control and
prevention measures. According to
word bank (2010) in Indonesia 20% of
the commercial farm workers lost their
jobs as a result of the outbreak. In
Vietnam, 44 million birds, or 17% of the
bird population, were culled at a cost of
$120 million.
Since 1997, multiple avian influenza
virus subtypes have been transmitted
directly from domestic poultry to
humans and have caused a spectrum

6. of human disease, from asymptomatic
to severe and fatal. Avian influenza
viruses occasionally affect mammals,
including humans, usually after close
contact with infected poultry. While
many human cases are limited to
conjunctivitis or mild respiratory
disease, some viruses tend to cause
severe illness.
The disease has an effect on
international trade. HPAI viruses can
kill up to 90-100% of the flock, and
cause epidemics that may spread
rapidly, devastate the poultry industry
and result in severe trade
restrictions. In 2004, Thailand was the
fourth largest exporter of poultry and
poultry products in the world. The
country exported 40% of its poultry
production, primarily to Europe and
Japan, but following the HPAI outbreak
and the ban on international trade of
poultry, its poultry industry was
economically devastated by losing 50%
of its export market (lokuge, 2005)
CONCLUSION
All in all, this paper has discussed
Avian Influenza as described in herd
health and production economics in
Malawi and the region. Avian Influenza
is a notifiable disease and it’s
significant to the public.
REFERENCES
i. Gordon,R.F.(1977).Poultry
Diseases. Bailliere
Tindall.London
ii. Lokuge B.( 2005).Avian
influenza, world food trade and
WTO rules: The economics of
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Rep. Work. Pap. Jan., The Aust.
Natl. Univ., Canberra
iii.Pattison,M.,Mcmullin,P.F.,Bradbu
ry,J.M.,and Alexander,D.J.
(2008).Poultry Diseases.6th
Edition.Saunders Elsevier
iv. Sainsbury,D.(1992).Poultry
Health and Management:
Chickens, Ducks, Turkeys,
Geese, Quail. Third
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7. Edition.Blackwell Scientific
Publications.London.
v. Scanes,G.C.,Brant,G.,and
Ensminger,M.E.(2004).Poultry
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vi. Shane,M.S.(2005).ASA
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AND PRODUCTION ECONOMICS
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