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Introduction

Paramyxovirus 1 or Newcastle Disease is a highly contagious viral disease affecting poultry of all ages. Affected species include chickens, turkeys, pigeons and ducks. The condition is rarely diagnosed in ducks but is a possible cause of production drops/fertility problems. Other species can be infected including mammals occasionally (e.g. conjunctivitis in man).

The virus involved is Paramyxovirus PMV-1, which is of variable pathogenicity. Signs are typically of disease of the nervous, respiratory or reproductive systems. Morbidity is usually high and mortality varies 0-100%. Higher mortality is seen in velogenic disease in unvaccinated stock.

Extracted From: A Pocket Guide to Poultry Health and Disease By Paul McMullin © 2004 Click Here to Order Your Copy

Four manifestations have been identified

• ND - Velogenic Viscerotropic (VVND) - sometimes called 'asiatic' or exotic. It is highly virulent for chickens, less for turkeys and relatively apathogenic in psittacines.
• ND - Neurotropic Velogenic - Acute and fatal in chickens of any age causing neurological and some respiratory signs. Intestinal lesions are absent.
• ND - Mesogenic - Mortality and nervous signs in adult. These viruses have sometimes been used as vaccines in previously immunised birds.
• ND - Lentogenic - Mild disease, sometimes subclinical. Can affect any age. Strains can be developed as vaccines.

Transmission is via aerosols, birds, fomites, visitors and imported psittacines (often asymptomatic). It is not usually vertical (but chicks may become infected in hatcheries from contaminated shells).

The virus survives for long periods at ambient temperature, especially in faeces and can persist in houses (in faeces, dust etc). for up to 12 months. However it is quite sensitive to disinfectants, fumigants and sunlight. It is inactivated by temperatures of 56°C for 3 hours or 60°C for 30 min, acid pH, formalin and phenol, and is ether sensitive.

Signs

Signs are highly variable and will depend on the nature of the infecting virus (see above), the infective dose and the degree of immunity from previous exposure or vaccination.

• Sudden Death
• Depression.
• Inappetance.
• Coughing.
• Dyspnoea.
• Diarrhoea.
• Nervous signs.
• Paralysis.
• Twisted neck.
• Severe drop in egg production.
• Moult.

   

Post-mortem lesions

• Airsacculitis.
• Tracheitis.
• Necrotic plaques in proventriculus, intestine, caecal tonsil.
• Haemorrhage in proventriculus.
• Intestinal lesions primarily occur in the viscerotropic form.

Diagnosis

A presumptive diagnosis may be made on signs, post-mortem lesions, rising titre in serology. It is confirmed by isolation in CE, HA+, HI with ND serum or DID (less cross reactions), IFA. Cross-reactions have mainly been with PMV-3. Pathogenicity evaluated by Mean Death Time in embryos, intracerebral or IV pathogenicity in chicks. Samples - tracheal or cloacal.

Differentiate from Infectious bronchitis, laryngotracheitis, infectious coryza, avian influenza, EDS-76, haemorrhagic disease, encephalomyelitis, encephalomalacia, intoxications, middle ear infection/skull osteitis, pneumovirus infection.

Treatment

None, antibiotics to control secondary bacteria.

Prevention

Figure 28. Severe haemorrhagic and necrotic lesions in proventriculus and Peyers patches in the intestines of a broiler chicken suffering from one of the severe forms of Newcastle disease (viscerotropic velogenic).

Quarantine, biosecurity, all-in/all-out production, vaccination. It is common to monitor response to vaccination, especially in breeding birds by the use of routine serological monitoring. HI has been used extensively; Elisa is now also used. These tests do not directly evaluate mucosal immunity, however.

Vaccination programmes should use vaccines of high potency, which are adequately stored and take into account the local conditions. A typical programme may involve Hitchner B1 vaccine at day old followed by LaSota-type vaccine at 14 days. The LaSota-type vaccine may even repeated at 35-40 days of age if risk is high. Use of spray application is recommended but it needs to be applied with care to achieve good protection with minimal reaction.

Inactivated vaccines have largely replaced the use of live vaccines in lay but they do not prevent local infections.

To prevent or reduce vaccinal reactions in young chicks it is important that day old have uniform titres of maternal immunity. Vaccinal reactions may present as conjunctivitis, snicking, and occasionally gasping due to a plug of pus in the lower trachea. In some countries it has been customary to provide antibiotics prophylactically during periods of anticipated vaccinal reaction. Use of Mycoplasma gallisepticum free stock under good management reduces the risk of vaccinal reactions

New Vaccine Developed to Fight Newcastle Disease

Newcastle disease (ND), which can be deadly for domestic and commercial poultry as well as wild bird populations, is a major concern worldwide for the poultry industry. Newcastle disease virus (NDV), which typically affects the respiratory, gastrointestinal and/or nervous system, causes disease in more than 250 species of birds.

Symptoms of ND can include coughing, gasping, diarrhoea, lack of appetite and drooping wings. Severe cases can result in mortality rates that exceed 90 per cent in susceptible chickens. To complicate matters, a quick diagnosis of an ND outbreak may be difficult because it can be confused with a clinically similar disease – avian influenza

Commercial poultry producers now use vaccines that protect vaccinated birds from disease but these vaccines do not prevent poultry from becoming infected and carrying virulent NDV or shedding it in their faeces. Infected birds can still spread the disease to healthy, unvaccinated birds.

USDA ARS scientists at the agency's Southeast Poultry Research Laboratory in Athens, Georgia, have developed a new vaccine that reduces mortality and severity of ND symptoms in poultry. The vaccine also decreases the amount of virulent virus shed from birds.

Microbiologist Qingzhong Yu in the ARS Endemic Poultry Viral Disease Research Unit and his colleagues in the ARS Exotic and Emerging Avian Viral Diseases Research Unit used reverse genetics technology to create a new vaccine that replaces a gene in the vaccine with a similar gene from the virulent NDV circulating in the environment today.

Dr Yu explained: "Currently, most vaccines used in the United States are formulated with NDV isolated in the 1940s, which is similar to the virulent NDV circulating at that time. Unfortunately, with time, new NDV strains have emerged that are genetically very different from commonly used vaccine strains

"

We found that when the new vaccine, which contains gene sequences similar to the virulent virus, was used in vaccination studies, the vaccinated birds were protected from disease and shed less of the virulent virus after challenge," he said.

Vaccines have been used for more than 50 years to control ND and are successful in reducing mortality and the severity of symptoms, Dr Yu says. However, ND continues to threaten the commercial poultry industry.

The most recent US outbreak in 2002-2003 affected poultry in several states: Arizona, California, Nevada and Texas. The industry suffered a devastating blow when more than 3.4 million birds had to be destroyed. California alone spent more than $160 million to control the outbreak.

The new vaccine protects birds from ND and reduces virus shedding, which will ultimately decrease the spread of the virulent virus