Newcastle disease (NCD, atypical avian influenza) is a highly contagious, acute to chronic disease of birds.

Worldwide

All birds

Direct transmission via all body fluids (faeces, eye, nose and throat secretions), indirect transmission via the air and objects. The virus can also be transmitted to the chick already in the egg.

4 to 7 days

Cold symptoms, neurological symptoms, diarrhoea. The clinical picture is reminiscent of avian influenza (bird flu)

There is no treatment for Newcastle Disease...

Newcastle Disease is a notifiable animal disease according to the Animal Health Law (AHL). Prophylactic vaccination is permitted in Austria and is also carried out in chickens, turkeys and pigeons (racing and breeding pigeons).

Newcastle disease last occurred in poultry in Austria in 1997. However, it occurs sporadically in wild pigeons and very rarely in domestic pigeons.

Newcastle disease is a notifiable animal disease. The appearance of clinically suspicious symptoms must be reported to the official veterinarian, who will take a sample and send it for examination. Only infections with highly virulent virus types that are detected using molecular genetic methods or are assessed according to a pathogenicity index (ICPI 0.7 or higher) are deemed to be an outbreak of the disease. If an outbreak of Newcastle disease is detected, all birds in the affected flock must be killed in accordance with the Animal Health Law (AHL).

Poultry farmers should ensure compliance with biosecurity measures: direct and indirect contact between poultry and wild birds should be prevented as far as possible. In the event of health problems in poultry farms, a veterinary examination should be carried out and Newcastle disease should be ruled out. For early detection and to prevent further spread, wild pigeons found dead must be reported to the locally competent district administrative authority (official veterinarian). Such animals should not be touched and should be left where they are found. The authorities will arrange for the pigeons to be recovered and examined. In light of the above, we would also like to point out that every poultry farm must be reported to the competent district administrative authority.

The causative agent of Newcastle disease is the Newcastle disease virus (avian avulavirus 1, APMV-1), a single-stranded RNA virus from the Paramyxoviridae family. NDV is assigned to the genus Avulavirus. A distinction is made between apathogenic, lentogenic (low virulence), mesogenic (low virulence) and velogenic (high virulence) virus types. The symptoms depend on the virulence of the pathogen.

In the bone marrow and muscles of slaughter poultry, the NCD virus remains infectious for 6 months at -20 ⁰C and up to 134 days at 1 ⁰C. In contaminated stables, the virus remains infectious for 25-30 days depending on the ambient temperature. The infectivity of the virus can be preserved for years by drying out.

Transmission can occur via the air, directly or via objects. The spread of the disease is favoured by the high tenacity of the virus and the broad host spectrum. Sources of infection are often clinically inapparent infected, diseased animals or animals in the incubation period.

NDV is excreted in large quantities via faeces, eye, nasal and throat secretions and all other body fluids. Virus excretion begins during the incubation period and, depending on the bird species affected, can last from 1-2 weeks to several months or about 1 year; in vaccinated animals about 2 weeks. The pathogens are spread directly from animal to animal as well as indirectly via all equipment, house dust and air, shoes and vehicles. Transovarial virus transmission plays a major role, whereby infected chicks hatch from NCD virus-contaminated eggs.

Trade in live or slaughtered poultry or their products plays a role in the introduction of the disease into disease-free regions (introduction also via frozen poultry!). Virus transmission is also possible via the feeding of kitchen waste, litter, feed, housing equipment and transport containers. In comparison, the probability of transmission via wild birds is low. With regard to wild birds, waterfowl and wild chickens are a natural reservoir for epidemics.

Newcastle disease is spread worldwide. The disease has become less significant in recent years due to control measures. In July 2018, an outbreak was reported in domestic chickens in Belgium.

At the National Reference Laboratory for Newcastle Disease (NRL, AGES Mödling), we analyse various bird samples for the presence of APMV-1 virus genome using real-time RT-PCR. Positive detections are further subtyped and confirmed by sequencing, egg culture and haemagglutination test (HA).

Real-time RT- PCR and sequencing:

Primary laboratory diagnosis is made by direct pathogen detection from tracheal/oropharyngeal (throat) and cloacal swabs and from animal carcasses (CNS, lung, liver, kidney, heart, intestine) using specific molecular biological methods (real-time RT-PCR). In the case of detection of NCD viruses, confirmatory methods are used to differentiate between virulent and avirulent subtypes. The NRL can differentiate between all currently occurring subtypes using DNA sequencing.

Whole genome sequencing is performed on selected samples (approx. 15.9kb). Enrichment is performed directly from clinical samples using a special RT-PCR, sequencing is performed using modern high-throughput devices (Next Generation Sequencing).

ELISA: The enzyme-linked immunosorbent assay is an antibody-based detection method. Antibodies present in the serum (vaccine and infection antibodies) bind to a specific antigen and are measured qualitatively or semi-quantitatively by means of an enzymatic colour reaction.

Haemagglutination inhibition test (HI): Special antibodies can prevent the agglutination (clumping) caused by the virus. In this way, antibody titres and specific antibodies directed against individual APMV-1 virus strains can be determined.

Virus cultivation in egg culture: A potentially infectious vaccine solution is prepared from the samples and used to inoculate guaranteed virus-free chicken eggs. These eggs are incubated for at least five days. If highly virulent APMV-1 viruses are present, the embryos in the eggs die and the virus in the allantios can be identified by haemagglutination (HA).

Haemagglutination test (HA): Certain viruses, such as APMV-1 viruses, use haemagglutinin to bind erythrocytes to their surface. This causes the blood to agglutinate (clot). The amount of virus can be determined by means of dilution series.

Differential diagnosis includes all diseases with

• acutely increasing mortality
• respiratory disorders
• disorders of the central nervous system (CNS)
• drop in laying performance
• Reduction in weight gain
• petechial haemorrhages due to seroses

z. e.g. avian influenza, avian cholera, infectious bronchitis, infectious laryngitis, Marek's disease, mycoplasmosis, deficiency symptoms, septic forms of bacterial infections.

In the event of the slightest suspicion, the official veterinarian responsible must send the legally prescribed samples to the National Reference Laboratory.

Sample type for sampling:

Live animals:

• Throat and cloacal swabs (dry, sterile, no bacteriological swab transport medium)
• Serum

Samples from dead animals:

• Organ material especially brain, lung, liver, kidney, heart, intestine
• Sample transport and short-term storage: at +4 °C