Newcastle disease
Encyclopedia
Newcastle disease is a contagious bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

 disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

 affecting many domestic and wild avian species. First found in Newcastle, United Kingdom in 1926, then by Burnet in 1943 in Australia in connection with laboratory infection where the virus was isolated from a ocular discharge of a patient to show the specific antibody
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

 titre in the patient's blood. Newcastle has a negative sense single stranded genome which codes for a RNA directed RNA polymerase
RNA polymerase
RNA polymerase is an enzyme that produces RNA. In cells, RNAP is needed for constructing RNA chains from DNA genes as templates, a process called transcription. RNA polymerase enzymes are essential to life and are found in all organisms and many viruses...

, hemagglutinin
Hemagglutinin
Influenza hemagglutinin or haemagglutinin is a type of hemagglutinin found on the surface of the influenza viruses. It is an antigenic glycoprotein. It is responsible for binding the virus to the cell that is being infected...

- neuraminidase
Neuraminidase
Neuraminidase enzymes are glycoside hydrolase enzymes that cleave the glycosidic linkages of neuraminic acids. Neuraminidase enzymes are a large family, found in a range of organisms. The most commonly known neuraminidase is the viral neuraminidase, a drug target for the prevention of the spread...

 protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

, fusion protein
Fusion protein
Fusion proteins or chimeric proteins are proteins created through the joining of two or more genes which originally coded for separate proteins. Translation of this fusion gene results in a single polypeptide with functional properties derived from each of the original proteins...

, matrix protein
Matrix protein
Viral matrix proteins are non structural proteins linking the viral envelope with the virus core. They play a crucial role in virus assembly, and interact with the RNP complex as well as with the viral membrane...

, phosphoprotein
Phosphoprotein
Phosphoproteins are proteins that are physically bonded to a substance containing phosphoric acid . This category of organic molecules includes Fc receptors, Ulks, Calcineurins, K chips, and urocortins....

 and nucleoprotein
Nucleoprotein
A nucleoprotein is any protein that is structurally associated with nucleic acid .Many viruses harness this protein, and they are known for being host-specific...

 in the 5' to 3' direction. Its effects are most notable in domestic poultry
Poultry
Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...

 due to their high susceptibility and the potential for severe impacts of an epizootic
Epizootic
In epizoology, an epizootic is a disease that appears as new cases in a given animal population, during a given period, at a rate that substantially exceeds what is "expected" based on recent experience . Epidemic is the analogous term applied to human populations...

 on the poultry industries. It is endemic
Endemic (epidemiology)
In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...

 to many countries.

Newcastle disease was discovered in Newcastle upon Tyne
Newcastle upon Tyne
Newcastle upon Tyne is a city and metropolitan borough of Tyne and Wear, in North East England. Historically a part of Northumberland, it is situated on the north bank of the River 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
Conjunctivitis
Conjunctivitis refers to inflammation of the conjunctiva...

 and influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...

-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.

Description

The causal agent, Newcastle disease virus, is a negative-sense single-stranded RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

. 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
Virulence
Virulence is by MeSH definition the degree of pathogenicity within a group or species of parasites as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenicity of an organism - its ability to cause disease - is determined by its...

), 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.

Use as an anticancer agent

In 1999, promising results were reported using an attenuated strain of the Newcastle virus, codenamed MTH-68, in cancer patients by researchers who had isolated the strain in 1968. It appears the virus preferentially targets and replicates in certain types of tumor cells, leaving normal cells almost unaffected. In 2006, researchers from the Hebrew University also succeeded in isolating a variant of the NDV, codenamed NDV-HUJ, which showed promising results in 14 glioblastoma multiforme
Glioblastoma multiforme
Glioblastoma multiforme is the most common and most aggressive malignant primary brain tumor in humans, involving glial cells and accounting for 52% of all functional tissue brain tumor cases and 20% of all intracranial tumors. Despite being the most prevalent form of primary brain tumor, GBMs...

 patients.

Use as a biological weapon

Newcastle disease was one of more than a dozen agents 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.

Symptoms

Signs of infection with NDV vary greatly depending on factors such as the strain
Strain (biology)
In biology, a strain is a low-level taxonomic rank used in three related ways.-Microbiology and virology:A strain is a genetic variant or subtype of a micro-organism . For example, a "flu strain" is a certain biological form of the influenza or "flu" virus...

 of virus and the health, age and species of the host
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...

.

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

They can include respiratory signs (gasping, coughing), nervous signs (depression, inappetence, muscular tremors, drooping wings, twisting of head and neck, circling, complete paralysis), swelling of the tissues around the eyes and neck, greenish, watery diarrhea, misshapen, rough- or thin-shelled eggs and reduced egg production.

In acute cases, the death is very sudden, and, in the beginning of the outbreak, the remaining birds do not seem to be sick. In flocks with good immunity, however, the signs (respiratory and digestive) are mild and progressive, and are followed after seven days by nervous symptoms, especially twisted heads.

Postmortem lesions

Petechiae in the proventriculus
Proventriculus
The proventriculus is part of the digestive system of birds, invertebrates and insects.-Birds:The proventriculus is a standard part of avian anatomy...

 and on the submucosae of the gizzard
Gizzard
The gizzard, also referred to as the ventriculus, gastric mill, and gigerium, is an organ found in the digestive tract of some animals, including birds, reptiles, earthworms and some fish. This specialized stomach constructed of thick, muscular walls is used for grinding up food; often rocks are...

 are typical; there is also severe enteritis of the duodenum. The lesions are scarce in hyperacute cases (first day of outbreak).

Immunological tests

Enzyme linked immunosorbent assay (ELISA), PCR, and sequence technology tests have been developed.

Samples


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.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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