مرض نيوكاسلNewcastle Disease Virus (NDV)

Newcastle Disease Virus (NDV)

Description:

-A type strain for avian paramyxoviruses. Members of this family have a single stranded, linear, RNA, with an elliptical symmetry. The total genome is roughly 16,000 nucleotides. Replication of the the virus takes place in the cytoplasm of the host cell.

NDV is a contagious and fatal viral disease affecting most species of birds. Clinical signs are extremely variable depending on the strain of virus, species and age of bird, concurrent disease, and preexisting immunity. Four broad clinical syndromes are recognized by scientists. They are Viscerotropic velogenic, Neurotropic velogenic, Mesogenic, and Lentogenic. NDV is so virulent that many birds die without showing any clinical signs. A death rate of almost 100 percent can occur in unvaccinated poultry flocks. NDV can infect and cause death even in vaccinated poultry. Fortunately NDV has not infected domestic chicken flocks in the

United States

since the last outbreak was eradicated in 1974.

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

. Amazon parrots that are carriers of the disease but do not show symptoms are capable of shedding NDV for more than 400 days.

Symptoms

: NDV affects the respiratory, nervous, and digestive systems. Symptoms are very variable depending on the strain of virus, species of bird, concurrent disease and preexisting immunity. The incubation period for the disease ranges from 2 to 15 days. An infected bird may exhibit the following signs:

Respiratory: sneezing, gasping for air, nasal discharge, coughing

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

Prevention

: Although often not recognized as such Exotic Newcastle is a threat to the caged-bird industry. Birds illegally smuggled into the

United States

are not quarantined and tested by the US Department of Agriculture (USDA) and therefore may carry the exotic Newcastle virus. Owners of pet birds should:

Request certification from suppliers that birds are legally imported or are of US stock, are healthy prior to shipment, and will be transported in new or thoroughly disinfected containers.

Maintain records of all sales and shipments of flocks. Isolate all newly purchased birds for at least 30 days. Restrict movement of personnel between new and old birds. Amazon parrots are difficult to raise domestically. Anyone who is offering to sell a large number of young parrots could be suspected of smuggling or purchasing smuggled birds.

Treatment

: There is no known treatment for Newcastle Disease.

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.

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مرض نيوكاسل

• مرض فيروسي شديد العدوى وواسع الانتشار.

• يصيب العديد من أنواع الطيور الداجنة من مختلف الأعمار.

• له أشكال مرضية مختلفة الحدّة في الدواجن.

• يسبب فيروس نيوكاسل نادرا التهاب طفيف فى ملتحمة العين فى الإنسان وبعض ذوات الثدي الأخرى

.طريقة انتشار العدوى:

•تفرز الطيور المريضة الفيروس فى الزرق واللعاب وإفرازات العيون والزفير.

•ينتقل فيروس نيوكاسل بين المزارع بواسطة الهواء ولكن لمسافات قصيرة.

•يدخل أيضاً إلى المزارع عن طريق الوسائط الملوّثة مثل: أحذية العاملين وموردى الأغذية والزوار؛ المعدات والأدوات المزرعية؛ الأقفاص؛ أكياس العلف؛ إطارات المركبات... الخ.

وتّدخله أحياناً الطيور البرية.

•تصاب الطيور عادة عن طريق الفم (علف أو ماء ملوّث) أو الأنف أو ملتحمة العين.

•ينتقل الفيروس أحياناً إلى بيض الطيور المصابة ولكن الأجنة المصابة تموت قبل الفقس.

أشكال المرض: للمرض ثلاثة أشكال:

•النوع الأحشائي الحاد: وهو نوع شديد الحدة ويسمّى أيضاً ”النوع الآسيوي“.

•النوع المتوسط: ويسمي أيضاً النوع العصبي.

•النوع الطفيف.

- فى معظم الأحيان تشاهد هذه الأشكال المختلفة بين أفراد القطيع الواحد أثناء الوباء.

فترة الحضانة: في المتوسط 4-6 أيام ومدّة المرض بالقطيع: 2-4 أسابيع ونسبة النفوق من 10-80% حسب حدّة المرض0

الأعراض:

• حشرجة الصوت.

• إفرازات من الأنف والعينين.