Salah M. Hassan
Newcastle disease virusNDV also called (avian paramyxovirus type I, pneumoencephalitis virus & pseudo-fowl pest). ND is contagious and fatal viral disease affecting most species of birds (chickens, turkeys, pigeons ,parrots ,ducks, geese, quails)and human. Taxonomy of the NDV : Family: Paramyxoviridae. Subfamily: Paramyxovirinae. Genus: Avulavirus.
Inactivation of the virus:
Haemagglutination:All strains of NDV agglutinate (Chicken, G.pig, human group O)RBCs. Most strains agglutinate (OX & sheep)RBCs. Horse RBCs agglutinated by lentogenic strain. NDV cause haemadsorption. Antigenic properties: NDV is immunologically distinct from orthomyxoviruses & from other members of paramyxoviruses. Mumps may develop HI antibodies to NDV.
Cultivation:
NDV is inoculated into 10-12 days hen embryonated eggs via chorioallantoic membrane or allantoic sac. It produces haemorrhagic lesions and encephalitis & embryo dies within 34-72 hours. NDV grows well in chicken embryo fibroblast cell culture. Maximum titer is obtained after 24-36 hours. Titer of the virus in tissue culture is one log lower than that in embryonated egg.Strains of NDV classified according to their pathogenicity into:
1. Viscerotropic velogenic NDV (Doyle's form). 2. Neurotropic velogenic NDV (Beache's form). 3. Mesogenic NDV (Beaudett's form). 4. Lentogenic NDV (Hitchner form). 5. Asymptomatic enteric NDV.Transmission:
Direct contact between healthy birds and the infected bird discharges. Contaminated feed, water, equipment and clothing. Virus can be picked up on shoes and clothing and carried from an infected flock to a healthy one. Airborne spread. Contaminated poultry vaccines. Other animals and birds transporting the virus from farm to farm.Pathogenicity:
the virulence of NDV Can be determined by the following techniques: 1. The mean death time in chicken egg embryo (MDT). 2. Intracerebral Pathogenicity index (ICPI) in day-old chick. 3. Intravenous Pathogenicity index (IVPI) in 6 week old chickens. 4. Intracloacal Pathogenicity test in 6-8 week old chickens.Incubation period:
It varies from (2 to 15) days in poultry depending on the virulence of the strain. In chickens infected with velogenic isolates; (2 to 6) days. In some avian species; 25 days. Pathogenesis: The virus replicates in the mucosa of the upper respiratory and intestinal tracts. Virus spreads via blood to spleen and bone marrow (viremia) causing infection of other organs: lung ,intestines & C.N.S.Immune response against NDV:
Antibody production is rapid. HI antibody can be detected within 4-6 days of infection. The level of HI antibody is a measure of immunity. Serum antibodies of the hen are transferred to chicks through yolk, and protect chicks for 3-4 weeks after hatching. Serum IgG does not prevent respiratory infection. Locally produced IgA prevent respiratory and the intestinal infection.Clinical Signs and Symptoms:
Respiratory symptoms. Nervous signs. Digestive symptoms. Drop in egg production with thin, rough-shelled eggs. Swelling of tissues around eyes and in the neck. Sudden death. In human;(Mild conjunctivitis, influenza-like symptoms and laryngitis).Fig9; Square appearance of the head due to bilateral facial edema.
Fig11; Reddening of periocular region and corneal edema.PM and gross lesions:
Inflammation with Petechial hemorrhages on proventriculus mucosa. Edematous, hemorrhagic, necrotic, and ulcerative areas on Peyer's patches, caecal tonsils. Edematous, hemorrhagic, or degenerated ovaries.Fig14; Odema and hemorrhages in the conjunctiva and infraorbital sinus.
Fig16; Mild haemorrhagic lesions in the mucosa of trachea.
Fig18; Sever thymus atrophy with extensive haemorrhages.Fig21; Extensive haemorrahges and ulcers of caecal tonsils mucosa.
Fig23; Focal ulceration and haemorrahge in the small intestine.Fig25; Sever haemorrhages in the rectal mucosa.
Fig27; Pulmonary congestion and edema.Fig29; Extensive haemorrhages on the liver.
Fig31;Sever acute haemorrahges and congestion in the ovarian follicles.
Diagnosis:It includes: 1. Clinical signs and symptoms. 2. Lab tests include; Serological tests: Haemagglutination inhibition test, Enzyme Linked Immunosorbant Assay (ELISA), PCR & Sequence technology. Pathogenicity assessment: Plaque test in chicken embryo fibroblast cultures. Mean death time. Intracerebral pathogenicity index. Intravenous pathogenicity index.