Newcastle_Disease (1)

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Newcastle Disease
By Rafael Lera, DVM
Poultry Veterinarian Hendrix Genetics Layers
Newcastle disease (ND) is a highly contagious disease of domestic poultry and other bird 
species considered of major importance worldwide. The disease has become enzootic in 
many regions of the world and has a huge global impact in the poultry industry because 
of production losses in case of outbreak. Occurrence must be reported to the OIE if some 
defined criteria for virulence are met, and can lead to trade restrictions.
Newcastle Disease is caused by strains of one 
serotype designated avian paramyxovirus-1 (APMV-
1). Strains are classified according to their virulence 
in pathotypes: asymptomatic (inapparent enteric 
infection), lentogenic (inapparent or mild respiratory 
infection), mesogenic (respiratory infection with 
possible neurologic signs) and velogenic (severe 
respiratory and nervous symptoms or gastrointestinal 
signs, causing high mortality).
NDV is transmitted airborne, by direct contact with 
secretions from infected birds (faeces or respiratory 
discharges) or indirect contact through contaminated 
feed, water, litter, equipment or people.
The virus may be destroyed by usual disinfectants 
but can survive for several weeks in organic matter.
Clinical Signs
Clinical signs vary widely and appear rapidly after 
exposure to virus, and depend on pathotype and 
age, young birds being the most susceptible.
Respiratory signs range from mild to severe: eye 
swelling, difficult breathing, coughing and rales and 
may be accompanied by nervous signs like tremors, 
birds moving in circles, paralysis and twisted necks. 
Watery greenish diarrhoea is frequently observed. 
Mortality is variable but can reach 100 % in virulent 
Newcastle Disease. 
In layer flocks, production can drop to 50 % or lower. 
Eggs may be deformed and show different shell 
defects (thin-shelled, rough, pale colour in brown 
eggs).
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Gross lesions are not specific to ND and depend 
also on strain and pathotype. Tracheitis, pneumonia 
and aerosacculitis are the main lesions found in the 
respiratory tract. Virulent viscerotropic NDV produce 
haemorrhages in many organs, commonly intestine, 
cecal tonsils, proventriculus (gizzard junction) and 
ovaries.
Paralysed bird with twisted neck
Haemorrhages of the organs caused by NDV
Diagnosis
Since clinical signs and gross lesions are not 
pathognomonic and vary widely with virus strain, 
suspicion of the disease should be confirmed by 
virus isolation from tissues and oropharyngeal or 
cloacal swabs.
Currently, RT-PCR is becoming a common and 
suitable test for screening and confirmation.
Serology (HI, ELISA) can help to diagnosis, if increase 
in paired serum samples is observed. These 
techniques have limitations for diagnosis: most of 
available ELISA kits cannot differentiate between 
field infection and vaccination. However, they are 
helpful as a monitoring tool to test response to 
vaccines
Control and vaccination
There is no treatment for Newcastle Disease: strict 
biosecurity is essential to prevent introduction of the 
virus. When the disease appears in an area where it 
is not enzootic, eradication by stamping out is the 
primary control strategy in many countries.
Different types of vaccines are available:
• Live-attenuated vaccines: lentogenic (e.g. 
Hitchner B-1, La Sota, VG/GA…) or mesogenic 
(e.g. Roakin). They can be used by mass 
vaccination (drinking water, spray) or individually 
(eye drop).
• Inactivated vaccines: commonly used after live 
vaccines for boosting and longer protection but 
also in combination with live vaccines from early 
age in endemic areas.
• Recombinant vaccines HVT-based: they can be 
administered the day of hatch, but it takes about 
4 weeks to develop significant immunity. In high 
ND challenge areas, additional live vaccines are 
required for proper protection.
Vaccination programs against ND should be adapted 
to field and challenge conditions. When risk of ND 
infection is significant, live vaccines can be given at 
regular intervals in production to maintain immunity.
Keep in mind that vaccines provide protection from 
clinical signs and minimize losses, but do not protect 
against infection or virus shedding. Vaccine failure 
is usually consequence of improper administration 
leading to significant % of the flock not immunized.
References
• MSD Animal Health Belgium, picture of bird with 
twisted neck (typical sign of Newcastle disease)