Virulent Newcastle disease

Newcastle disease virus
Virus classification
Group:	Group V ((−)ssRNA)
Order:	Mononegavirales
Family:	Paramyxoviridae
Genus:	Avulavirus
Species:	Newcastle disease virus

Newcastle disease is a contagious bird disease affecting many domestic and wild avian species. Its effects are most notable in domestic poultry due to their high susceptibility and the potential for severe impacts of an epidemic on the poultry industries. It is endemic to many countries.

Newcastle Disease was discovered in Newcastle upon Tyne, England in 1926 (Doyle), but also at this time slightly different strains were found in other parts of the world.

Exposure of humans to infected birds (for example in poultry processing plants) can cause mild conjunctivitis and influenza-like symptoms, but the Newcastle disease virus (NDV) otherwise poses no hazard to human health. Interest in the use of NDV as an anticancer agent has arisen from the ability of NDV to selectively kill human tumour cells with limited toxicity to normal cells.

No treatment for NDV exists, but the use of prophylactic vaccines and sanitary measures reduces the likelihood of outbreaks.

The causal agent

Description

The causal agent, Newcastle disease virus (NDV), is a negative-sense single-stranded RNA virus. Transmission occurs by exposure to faecal and other excretions from infected birds, and through contact with contaminated feed, water, equipment and clothing.

Strains

NDV strains can be categorised as velogenic (highly virulent), mesogenic (intermediate virulence) or lentogenic (nonvirulent). Velogenic strains produce severe nervous and respiratory signs, spread rapidly and cause up to 90% mortality. Mesogenic strains cause coughing, affect egg quality and production and result in up to 10% mortality. Lentogenic strains produce mild signs with negligible mortality.

Newcastle disease variant

In 1999, promising results were found using the Newcastle virus in cancer patients. In 2006 researchers from the Hebrew University have succeeded in isolating a variant of the Newcastle Disease Virus (NDV-HUJ), in order to specifically target cancer cells [1]. NDV-HUJ is a natural variant of NDV Virus and is also an attenuated variant (e.g., weakened virus), it innately preferentially targets and replicates in certain types of tumor cells (brain and lung), leaving normal cells almost unaffected. The researchers tested the new Viro-therapy on 14 Glioblastoma multiforme patients and achieved promising results for the first time.

Use as a biological weapon

Newcastle disease was one of more than a dozen agents that the United States researched as potential biological weapons before the nation suspended its biological weapons program.

Transmission

NDV is spread primarily through direct contact between healthy birds and the bodily discharges of infected birds. The disease is transmitted through infected birds' droppings and secretions from the nose, mouth, and eyes. NDV spreads rapidly among birds kept in confinement, such as commercially raised chickens.

High concentrations of the NDV are found in birds' bodily discharges; therefore, the disease can be spread easily by mechanical means. Virus-bearing material can be picked up on shoes and clothing and carried from an infected flock to a healthy one.

NDV can survive for several weeks in a warm and humid environment on birds' feathers, manure, and other materials. It can survive indefinitely in frozen material. However, the virus is destroyed rapidly by dehydration and by the ultraviolet rays in sunlight. Smuggled pet birds, especially Amazon parrots from Latin America, pose a great risk of introducing NDV into the US. Amazon parrots that are carriers of the disease but do not show symptoms are capable of shedding NDV for more than 400 days.

Clinical symptoms

Torticollis in a mallard with Newcastle Disease

Signs of infection with NDV vary greatly depending on factors such as the strain of virus and the health, age and species of the host.

They can include respiratory signs (gasping, coughing), nervous signs (depression, inappetence, drooping wings, paralysis), swelling of the eyes and neck, diarrhoea, misshapen, rough- or thin-shelled eggs and reduced egg production.

The incubation period for the disease ranges from 2 to 15 days. An infected bird may exhibit the following signs:

Digestive: greenish, watery diarrhea

Nervousness, depression, muscular tremors, drooping wings, twisting of head and neck, circling, complete paralysis

Partial to complete drop in egg production and thin-shelled eggs

Swelling of the tissues around the eyes and in the neck

Sudden death

Diagnosis

Enzyme Linked Immunosorbant Assay (ELISA), PCR, Sequence technology.

Sample

For routine isolation of NDV from chickens, turkeys, and other birds, samples are obtained by swabbing the trachea and the cloaca. Cotton swabs can be used. The virus can also be isolated from the lungs, brain spleen, liver, and kidneys.

Handling

Prior to shipping samples should be stored at 4 C. (refrigerator). Samples must be shipped in a padded envelope or box. Samples may be sent by regular mail, but overnight is recommended.

Prevention

Any animals that are showing symptoms of Newcastle Disease should be quarantined immediately. New birds should also be vaccinated before being introduced to your flock. There is an inactivated viral vaccine available, as well as various combination vaccines.

References

• Nelson CB, Pomeroy BS, Schrall K, Park WE, Lindeman RJ. (1952). An outbreak of conjunctivitis due to Newcastle disease virus (NDV) occurring in poultry workers. Am J Public Health 42(6):672–8.

External links

• Discount MBT shoes
• World Organisation for Animal Health (OIE)
• Department of Environment, Food and Rural Affairs, UK
• CSIRO, Australia
• Discount MBT shoes - An IsraCast article
• United States Animal Health Association VELOGENIC NEWCASTLE DISEASE [2]
• Iowa State University Department of Veterinary Pathology, Center for Food Security and Public Health, "Newcastle Disease" [3]