Geographical distribution of Newcastle diease between July and December 2010
Highly contagious and infectious disease affecting birds and more often galliforms. It is caused by a type 1 avian paramyxovirus.
The clinical forms of the disease vary. In the classic form general health is affected and is accompanied by digestive, respiratory and/or nervous disorders. The more severe forms progress rapidly towards death.
As a major problem in poultry farming (high contagiousness, clinical seriousness), the disease leads to significant economic loss.
Enzootic disease in many parts of the world, especially in various tropical areas such as South and central America. It's present in the Caribean.
Domestic and wild birds, especially galliforms, but also pigeons ("pigeon paramyxoviruses") and psittacines. Ducks are little affected by the disease.
Receptivity and susceptibility factors
Age (young animals), species, stress.
An enveloped RNA virus from the family Paramyxoviridae, of the Rubulavirus genus, serogroup 1.
Pathogenicity varies depending on the strain involved (lentogenic, mesogenic or velogenic strain), the species affected and tissue tropism of the infecting strain (viscerotropic, neurotropic, pneumotropic).
Strain virulence can be determined using an ICPI index (Intracerebral Pathogenicity Index). ICPI >= 0.7: mesogenic or velogenic strain.
The virus is highly resistant in droppings and survives in carcasses, egg shell (7-8 months) and in the ground (3 months).
Newcastle disease is clinically indistinguishable from Avian Influenza.
Incubation period: 5-7 days on average, [3 days; 21 days].
The symptoms vary depending on strain virulence, tropism, the host species and the infected animal itself (residual immunity).
Subacute form
Septicaemia and death in 1 or 2 days.
Classic acute form
3 phases:
Invasive phase:
• General health is affected: loss of appetite, ruffled feathers, falls and laying abnormalities.
• Followed by: cyanosis, petechia and underlying oedema of the comb, neck and wattles.
Stable phase: signs are seen in a single animal or several animals.
• digestive disorders: abundant greenish diarrhoea.
• respiratory disorders: discharge, dyspnea and coughing.
• nervous disorders: encephalitis (convulsion, loss of balance, paralysis, etc.)
Terminal phase:
• either aggravation and death
• either clinical improvement with persistence of nervous sequelae and maying abnormalities.
Subacute or chronic form
Respiratory disorders. General health is not affected. Sometimes a drop in egg production occurs as do abnormal behaviour and diarrhoea. Mortality may be high.
Asymptomatic form
Very frequent and caused by lentogenic strains which are detected by virological analysis.
No specific treatment exists.
Sanitary prophylaxis
Insufficient during an epizootic or in an enzootic area.
• Defensive measures:
Inspection on importation, general hygiene, disease-free guarantee in egg and chick purchase.
• Offensive measures:
Culling of all infected batches and destruction of carcasses and eggs followed by disinfection and depopulation of 21 days.
Often unenforceable (as costly) or insufficient (rapid dissemination of the disease).
Medical phrophylaxis
Necessary in infected or high-risk areas. The vaccination considerably reduces the loss in poultry flocks.
Different protocols exist according to species, age and the epidemiological context.
Animal sanitary status must be taken into account: risk of aggravation of the reaction to the vaccine by Mycoplasma (use an inactivated virus vaccine in this case).
Control the level of protection offered by the vaccine by regular serological screening (haemagglutination inhibition test).
Inactivated or modified virus vaccines (Hitchner B1, Clone 30, La Sota, VG/GA) are available.
Live B1 and La Sota strains can be administered in drinking water or as a spray (mass vaccination).
Chicks may be vaccinated as early as 1-4 days' old but the vaccine is most effective when administered from 2-3 weeks of age.