Today we
will be discussing about one of the most ruthless diseases in poultry
production.
What is Newcastle Disease?
Newcastle
Disease is a highly contagious viral infection that affects many species of
domestic and other bird species with virulent Newcastle disease virus (NDV).
Domestic
fowls, turkeys, pigeons are most susceptible while a mild form of the disease
affects ducks, geese, quail and guinea fowl. It is a worldwide problem that
presents primarily as an acute respiratory or digestive disease, or diarrhoea
may be the predominant clinical form an ad drop in egg production, profuse
diarrhoea followed by collapse, or long-term nervous signs (such as twisted
necks), if the birds survive.
Severe forms
of the disease are highly fatal.
What Causes Newcastle Disease?
Newcastle
Disease is caused by a paramyxovirus that can vary in pathogenicity from mild
to highly pathogenic.
Onset of the
disease is rapid, and signs appear throughout the flock within 2 to 12 days
(average 5) after aerosol exposure. Young birds are the most susceptible.
Observed
signs depend on whether the infecting virus has a predilection for respiratory,
digestive, or nervous systems.
Ways of Contamination
Spread is
usually by direct physical contact with infected or diseased birds. The virus
is present in litter and is breathed out into the air.
Other
sources of infection are contaminated equipment, carcasses, water, food and
clothing. People can easily carry the virus from one shed or farm to another.
Newcastle
Disease virus does not affect humans in the same way that it does birds but it
can cause conjunctivitis in humans.
Signs of Newcastle Diseases
1. Nervous Signs:
Nervous
signs of Newcastle diseases are; tremors, paralyzed wings and legs, twisted
necks, circling, clonic spasms, and complete paralysis may accompany, but
usually follow, the respiratory signs in neurotropic velogenic disease. Nervous
signs with diarrhoea are typical in pigeons, and nervous signs are frequently
seen in exotic bird species.
2. Respiratory Signs:
Respiratory
signs of Newcastle diseases are; watery greenish diarrhoea, and swelling of the
tissues of the head and neck are typical of the most virulent form of the
disease, viscerotropic velogenic Newcastle disease, although nervous signs are
often seen, especially in vaccinated poultry. Varying degrees of depression and
inappetence are seen. Partial or complete cessation of egg production may
occur. Eggs may be abnormal in colour, shape, or surface and have watery
albumen. Mortality is variable but can be as high as 100% with NDV infections.
Well-vaccinated birds may not show any signs of being infected except for
a decrease in egg production, but these birds will shed virus in saliva and faeces.
Poorly vaccinated birds may develop torticollis, ataxia, or body and head
tremors 10 to 14 days after infection and may recover with supportive care.
Prevention and Treatment of Newcastle
Disease
There is no
treatment for Newcastle Disease, although treatment with antibiotics to control
secondary infections may assist. The virus can remain alive in manure for up to
2 months and in dead carcasses for up to 12 months, however it is easily killed
by disinfectants, fumigants and direct sunlight. Prevention relies on good
quarantine and biosecurity procedures and vaccination. Newcastle Disease
vaccination of commercial meat and egg layer chickens is advisable.
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