Newcastle Disease (ND)

Cause
 Newcastle disease is caused by a Paramyxovirus (APMV-1). Only one serotype of ND is known. ND virus has mild strains (lentogenic), medium strength strains (mesogenic), and virulent strains (velogenic).
The strains used for live vaccines are mainly lentogenic.

Transmission
 Newcastle disease virus is highly contagious through infected droppings and respiratory discharge between birds. Spread between farms is by infected equipment, trucks, personnel, wild birds or air. The incubation period is variable but usually about 3 to 6 days.

Species affected
Chickens and turkeys.

Clinical signs
Highly pathogenic strains (velogenic) of ND cause high mortality with depression and death within 3 to 5 days. Affected chickens do not always exhibit respiratory or nervous signs. Mesogenic strains cause typical signs of respiratory distress.
Labored breathing with wheezing and gurgling, accompanied by nervous signs, such as paralysis or twisted necks (torticollis) are the main signs. Drop in egg production 30 to 50 % or more, returning to
normal levels in about 2-3 weeks is observed. Besides also egg shell quality will be affected (thin, loose color). In well-vaccinated chicken flocks clinical signs may be difficult to find.

Intestinal lesions
Inflamed tracheas, pneumonia, and/or froth in the airsacs are the main lesions. Haemorrhagic lesions are observed in the proventriculus and the intestines.

Diagnosis
Clinical signs followed by laboratory confirmation. Be aware that other respiratory infections like Infectious Bronchitis, Infectious Laryngotracheitis and Avian Influenza can give similar signs.
Confirmation can be obtained with virus isolation and identification
from tracheal or cloacal swabs, or PCR (Polymerase Chain Reaction), Serology testing with HI or Elisa measures the antibody response after infection. Be aware that vaccination also induces antibody response.

Treatment
There is no specific treatment for ND; antibiotic treatment of secondary bacterial infections (eg E.coli) will reduce the losses.