newcastle disease virus

Newcastle disease virus

NDV 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.

Characteristics: Spherical virus with diameter of 100-300 nm. Enveloped virus (containing lipid, CHO & protein). It has segmented & single stranded negative sense RNA. 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%.

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.

CPE of NDV: Syncytia formation. Production of inclusion bodies. Haemadsorption of G.pig RBCs by infected cell culture.

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.

Diagnostic Samples:Samples from live birds: Tracheal swabs. Cloacal swabs. Faecal swabs. Serum. Samples from dead birds: Lung, kidneys, intestine, spleen, brain, liver, and heart

tissues.

Differential diagnosis: Pathogenic avian influenza. Infectious laryngotracheitis. Salmonellosis & Mycoplasmosis. Vit. E and Selenium deficiency. Avian encephalomyelitis. Infectious bronchitis. Fowl cholera. Fowl pox. Coryza.

Treatment: There is no known treatment for Newcastle Disease.

Prevention: Quarantine & isolation of all newly purchased birds for at

least 30 days. 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.

Vaccination: Vaccines are administrated at 2 to 4 weeks of age or at 1 day

of age via conjunctival instillation. Vaccine-induced immunity is short-lived (8–10) weeks.Live vaccine.Inactivated vaccine.Newplex (a proprietary virus antibody

complex vaccine).

REFERENCES: http://www.fst.osu.edu/li/research.htm http://www.spc.int/rahs/Manual/AVIAN/NEWCASTLE.htm http://www.daff.gov.au/animal-plant-health/pests-diseases-weeds/animal/

newcastle http://www.cfsph.iastate.edu/DiseaseInfo/clinical-signs-photos.php?

name=newcastle-disease www.webconferences.com/.../ppt/Newcastle%20Disease

%20Virus_Samal.pdf www.fao.org/docrep/003/t0756e/T0756E08.htm Clubb, S. Laws and Regulations Affecting Aviculture and the Pet Bird Industry.

Altman, R; Clubb, S; Dorrestein, G; Quesenberry, K. (eds.). Avian Medicine and Surgery. W.B. Saunders. Philadelphia, PA; 1997.

Gallerstein, G; Acker, H. The Complete Bird Owner's Handbook. Simon & Schuster Macmillan. New York, New York; 1994.

Olsen, G; Orosz, S. Manual of Avian Medicine. Mosby, Inc. St. Louis, MO; 2000.

Rupley, A. Manual of Avian Practice. W.B. Saunders. Philadelphia, PA; 1997. USDA Department of Agriculture. Veterinary Services. Exotic Newcastle

Disease. May, 2001.