Newcastle Disease First identified in Newcastle in 1926, (Java) ND is contagious and fatal viral disease affecting most species of birds (chickens, turkeys, pigeons, parrots, ducks, geese, quails) and human. Considered the most serious poultry disease worldwide Respiratory tract and multi-organ systemic disease with a near 100% mortality rate So rapidly acting that birds may die without showing any clinical signs Endemic to Asia, the Middle East and Africa – where H5N1 Avian Influenza is also established Occurs in Europe, Australia and North America

Taxonomy of the NDV : Family: Paramyxoviridae. Subfamily: Paramyxovirinae. Genus: Avulavirus.

Characteristics: The virus is enveloped, roughly spherical, with a diameter around 100-300 nm. Enveloped virus (containing lipid, CHO & protein). The genome is segmented & single stranded negative sense RNA consisting of 15,186 nucleotides. Two specific virus proteins (hemagglutinin-neuraminidase & fusion protein) are the main proteins found in the outer coat of the virus. Replication occurs in the cytoplasm of the host cell. Affected species; birds & human. Morbidity; Up to100% & Mortality; 90%.

Fig1; Diagrammatic representation of Newcastle disease virus.

Inactivation of the virus: Minimum core temperature of 80°C for one minute, 75°C for 5 minutes or 70°C for 30 minutes - completely destroys the virus in meat. Ether sensitive and inactivated by formalin, phenol & acid pH. Destroyed rapidly by dehydration and ultraviolet rays. pH 3 - 3 min

Antigenic properties: 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 Strains of NDV classified according to their pathogenicity into: 1. Velogenic – highly lethal to all life history stages, cause severe intestinal and/or neurologicdisease resulting in high mortality –Neurotropic (Beache's form). –Viscerotropic (Doyle's form). 2. Mesogenic (Beaudett's form)– deadly to embryos and younger birds, cause respiratory or nervous signs with moderate mortality. 3. Lentogenic (Hitchner form)– mild or asymptomatic respiratory infection, cause mild or inapparent respiratory disease. 4. Asymptomatic enteric NDV. Exotic Newcastle Disease = Velogenic & Mesogenic

To differentiate among the pathotypes The Mean Death Time (MDT) of embryos, the Intracerebral Pathogenicity Index (ICPI), Intravenous Pathogenicity Index (ICPI) and plaque on the tissue culture are used. Enzootic ND Lentogenic - mild - kills embryos in > 90 hours Mesogenic - moderate - kills embryos in 60-90 hours Velogenic - highly virulent neurotropic or viscerotropic - kills embryos in < 60 hours Velogenic strains are now officially designated as Exotic Newcastle Disease (END) Lentogenic & mesogenic are used as vaccine strains. Hitchner: B1 - B1 – milder, La Sota: B1 - La Sota - more virulent.

Incubation period: Pathogenesis: 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.

Transmission Spread primarily via bodily discharges of birds Infected birds droppings Secretions from the nose, mouth and eyes Dissemination by contaminated animals and humans to susceptible birds Infected carriers (e.g., parrots) capable of shedding virus for > 1 year

Clinical Signs and Symptoms: Signs vary with species and virulence Greenish, dark watery diarrhea 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. Surviving birds may have neurological or reproductive damage In human;(Mild conjunctivitis, influenza-like symptoms and laryngitis).

Exotic Newcastle Disease Clinically indistinguishable from Highly Pathogenic H5N1 Avian Influenza Birds often destroyed based on visual diagnosis of Newcastle Disease and without H5N1 testing   Thus, H5N1 infections may remain undetected Photos: New South Wales Agriculture, Australia

PM and gross lesions: Inflammation with Petechial hemorrhages on mucosal membranes (proventriculi, isthmus of gizzard, trachea and pharynx). Edematous, hemorrhagic, or necrotic foci , and ulcerative areas on Peyer's patches, caecal tonsils. Edematous, hemorrhagic, or degenerated ovaries. Diphtheriod inflammation on lymphoid tonsils on pharynx Severe inflammation of air sacs. Pet bird may have mild non-specific lesions and no gross lesions. (Can have severe enteric type). CNS histopathological lesions are present but must be differentiated from AE and MD

Diagnosis: It includes: 1. History, Clinical signs and gross lesions. 2. Lab tests include; Virus isolation Serological tests: Haemagglutination inhibition test, VN - with known ND antisera, Enzyme Linked Immunosorbant Assay (ELISA), (No strain information,Cannot differentiate infected from vaccinated animals, May be used post-vaccination to confirm immune response) PCR & Sequence technology. Pathogenicity assessment: Plaque test in chicken embryo fibroblast cultures. Mean death time. Intracerebral pathogenicity index. Intravenous pathogenicity index.

Diagnostic Samples: Tracheal swabs. Cloacal swabs. Faecal swabs. Samples from live birds: Tracheal swabs. Cloacal swabs. Faecal swabs. Serum. Samples from dead birds: Lung, kidneys, intestine, spleen, brain, liver, and heart tissues. In cases of mixed viral respiratory infection, NDV will show up in the embryos before IBV.

Differential Diagnosis Infectious bronchitis – respiratory Laryngotracheitis – respiratory Avian encephalomyelitis – neurological Vitamin E & selenium deficiency – neurological Mycotic encephalitis – neurological Avian influenza - variable pathogenicity

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.

Treatment: Prevention: None Broad spectrum antibiotics for secondary bacterial involvement Prevention: Quarantine & isolation of all newly purchased birds. Transportation of birds in new or disinfected containers. Restrict personnel movement between new and old birds. Disinfection of all surfaces and equipment. Disposal of any destroyed birds and contaminated products. Removal of insects and mice (vectors). Control handling of bird carcasses, litter and manure.

Enzootic ND Vaccination: Live Virus; B1, La Sota Killed Virus in oil adjuvant, produced with B1 virus. Maternal antibodies interfere with active immunity buffering the expected vaccine reaction. Enzootic Immature Birds - broilers, leghorn pullets, etc. Vaccinated with live vaccines usually at 1 to 4 days and at around 14 to 28 days. This virus doesn’t replicate in the Harderian gland, so lower maternal antibody is desired to prevent vaccine blockage. Breeders & Leghorns - give killed vaccine at around 12-18 wks. of age after being primed with live vaccine.