The virus (NDV) is relatively stable in nature, remaining infective for weeks at low temperature and surviving for several hours in a wide range of ph (3-10). In litter it can survive for 20 days, and in water, soil, carcasses, eggs and feathers for 255 days. It survives in meat and bone for 6 months at 1 º C., but can be eliminate by paasteurization of eggs and egg products at 64 º C for 4.5 minutes, rendering for several minutes at 100 º C, processing meat for 30 minutes at 30 º C or 1 minute at 80 º C. Transmission is by contact with infected products or by aerosol from infected live birds. Mechanical transmission between premises can occur on footwear, clothing, skin, feed, trucks, and poultry or egg handling equipment.
The incubation period is 2-6 (up to 15) days. In chickens, outbreaks may be so severe that almost all of the affected flock may dies within 72 hours without showing clinical signs. Pidgeons can show mortality of up to 80%, while ducks and geese are usually less than 10%, although large die-oofs have been report in the wild. Canaries generally show a mild disease with low mortality.
Humans can be infected with NDV, with headache, flu-like symptoms and mild conjunctivitis (4-7 days) rarely becoming severe or leading to visual impairment. Most infections are in laboratory personnel.
Pathogenic strains of ND cause sudden onset of depresssion, rapid breathing and anorexia in all ages of birds, and a sharp drop in egg production in laying hens. The viscerotropic pathogenic strain may cause edema of the head and bright green or bloody diarrhea as prominent clinical features. Neurogenic pathogenic strains are characterized by marked nervous signs such as torticollis (twisting of the neck), tremors or paralysis. Mobidity and mortality with all pathogenic strains may rapidly exceed 90% in chickens and turkeys. Infected pet birds may show mild to severe respiratory, enteric and/or neurologic signs and shed virus for several months.
Pathogenic strains are exotic in commercial poultry operations in Canada. The major risk is from migratory wild birds carrying the disease into the country, or from undeclared infected pets birds (especially psittacine) brought into Canada from other countries.
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Surveillance: Special Issue - Exotic Diseases, Vol 23,
MAF Regulatory Authority, Ministry of Agriculture
P.O. Box 2526, Wellington, New Zealand
Poultry Diseases, Fourth Edition
Jordon, F.T.W. and Pattison, M., Editors
W.B. Saunders Company Ltd., London, 1996 , ISBN 0-7020-1912-7
Notifiable Diseases: Special Issue of the State Veterinary Journal,
Vol. 5 No. 3, October 1995
Ministry of Agriculture, Fisheries and Food, United Kingdom ISSN:0269 5545
Exotic Diseases of Animals: A Field Guide for Australian
Geering, W.A., Forman, A.J. and Nunn, M.J.
Australian Government Publishing Service, Canberra, 1995, ISBN 0 644 33513 0
Avian Disease Manual, Third Edition
Whiteman, C.E. and Bickford, A.A.
American Association of Avian Pathologists
Kendall/Hunt Publishing Company,Dubuque, Iowa, ISBN 0-8403-5795-8
The Merck Veterinary Manual, 6th Edition, Editor: Fraser,
Merck & Co., Inc, Rahway, N.J., U.S.A., 1986, ISBN 911910-53-0