Newcastle disease
Aetiology Epidemiology Diagnosis Prevention and control References
AETIOLOGY
Classification of the causative agent
Virus family Paramyxoviridae, genus Rubulavirus
Temperature: Inactivated by 56°C/3 hours, 60°C/30 min pH: Inactivated by acid pH Chemicals: Ether sensitive Disinfectants: Inactivated by formalin and phenol Survival: Survives for long periods at ambient temperature, especially in faeces EPIDEMIOLOGY
Hosts
- Many species of birds, both domestic and wild
- The mortality and morbidity rates vary among species, and with the strain of virus
- Chickens are the most susceptible poultry, ducks and geese are the least susceptible poultry
- A carrier state may exist in psittacine and some other wild birds
Transmission
- Direct contact with secretions, especially faeces, from infected birds
- Contaminated feed, water, implements, premises, human clothing, etc.
Sources of virus
- Respiratory discharges, faeces
- All parts of the carcass
- Virus is shed during the incubation period and for a limited period during convalescence
- Some psittacine birds have been demonstrated to shed ND virus intermittently for over 1 year
Occurrence
Newcastle disease is endemic in many countries of the world. Some European countries have been free of the disease for years
For detailed information on occurrence, see recent issues of World Animal Health and the OIE Bulletin
DIAGNOSIS
Incubation period is 4-6 days
Clinical diagnosis
- Respiratory and/or nervous signs:
- gasping and coughing
- drooping wings, dragging legs, twisting of the head and neck, circling, depression, inappetence, complete paralysis
- Partial or complete cessation of egg production
- Eggs are misshapen, rough-shelled, thin-shelled and contain watery albumen
- Greenish watery diarrhoea
- Swelling of the tissues around the eyes and in the neck
- Morbidity and mortality depend on virulence of the virus strain, degree of vaccinal immunity, environmental conditions, and condition of the flock
Lesions
- There are no pathognomonic gross lesions
- Several birds have to be examined to make a tentative diagnosis
- Final diagnosis must await virus isolation and identification
- Lesions that may be found are:
- oedema of the interstitial or peritracheal tissue of the neck, especially near the thoracic inlet
- congestion and sometimes haemorrhage on tracheal mucosa
- petechiae and small ecchymoses on the mucosa of the proventriculus, concentrated around the orifices of the mucous glands
- oedema, haemorrhages, necrosis or ulcerations of lymphoid tissue in the intestinal wall mucosa
- oedema, haemorrhages or degeneration of ovaries
Differential diagnosis
- Fowl cholera
- Avian influenza
- Laryngotracheitis
- Fowl pox (diphtheritic form)
- Psittacosis (chlamydiosis) (psittacine birds)
- Mycoplasmosis
- Infectious bronchitis
- Pacheco's parrot disease (psittacine birds)
- Also management errors such as deprivation of water, air, feed
Laboratory diagnosis
Procedures
Identification of the agent
- Inoculation of 9-11-day-old embryonated chicken eggs followed by:
- examination of haemagglutination activity
- inhibition of haemagglutination by ND virus-specific antiserum
Pathogenicity assessment
- Plaque test in chicken embryo fibroblast cultures
- Mean death time of embryonated chicken eggs
- Intracerebral pathogenicity index in 1-day-old chickens
- Intravenous pathogenicity index (IVPI) in 6-week-old chickens
Serological tests
- Haemagglutination inhibition test
- ELISA
Samples
Identification of the agent
- Tracheal and cloacal swabs (or faeces) from live birds or from pools of organs and faeces from dead birds
Serological tests
- Clotted blood samples or serum
PREVENTION AND CONTROL
No treatment
Sanitary prophylaxis
- Strict isolation of outbreaks
- Destruction of all infected and exposed birds
- Thorough cleaning and disinfection of premises
- Proper carcass disposal
- Pest control in flocks
- Depopulation followed by 21 days before restocking
- Avoidance of contact with birds of unknown health status
- Control of human traffic.
- One age group per farm ('all in-all out') breeding is recommended
Medical prophylaxis
- Vaccination with live and/or oil emulsion vaccines can markedly reduce the losses in poultry flocks
- Live B1 and La Sota strains are administrated in drinking water or as a coarse spray. Sometimes administered intranasally or intraocularly. Healthy chickens may be vaccinated as early as day 1-4 of life, but delaying vaccination until the second or third week increases its efficiency
- Some other infections (e.g. Mycoplasma) may aggravate the vaccine reaction. Killed virus vaccine should then be used
REFERENCES AND OTHER INFORMATION
- Reference experts and laboratories
- Classified as an OIE List A disease (A160)
- Chapter 2.1.15. in the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals.
- Terrestrial Animal Health Code
- Other references - see the Index
- World Animal Health.
- Current Animal Health Status (Disease Information)
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Contact : scientific.dept@oie.int