Avian Influenza

(Fowl Plague)

Avian Influenza (AI) is an infectious disease caused by a virus that can affect both wild birds and domestic fowl. There are different influenza viruses (A,B,&C), but only influenza A viruses have been isolated from avian species. These are further divided into subtypes determined by antigens H (hemagglutinin) and N (neuraminidase). There are 12 H subtypes and 9 N subtypes, and each virus has one of each subtype in any combination. Within this type, only a few subtypes containing H5 or H7 will cause the Highly Pathogenic Avian Influenza (HAPI) called Fowl Plague, the virulent form of AI.

HAPI is highly contagious and may cause high mortality in poultry in association with respiratory, gastrointestinal and/or nervous signs. In some other avian species, AI virus infection may range clinically from an inapparent to a highly fatal disease.

HPAI has never been reported in Canada, however AI viruses of most H and N subtypes may be isolated from a wide range of wild waterbirds including migratory species. An AI virus virulent for domestic poultry could emerge from the pool of AI viruses in wild birds at any time. HAPI outbreaks occurred in Mexico in 1995 and in the United States in 1983-84. That outbreak in Pennsylvania, New Jersey, Maryland and Virginia was eradicated at a cost of $62 million and 17 million birds were destroyed.

Direct or indirect contact with migratory waterfowl is the most likely source of infection in poultry. AI virus from waterfowl can remain viable in feces and water for up to 32 days. AI can spread through contaminated materials such as bird cages, pallets, eggs, manure and feedstuffs, and from people going from farm to farm withought appropriate cleaning and disinfection procedures. Biosecurity of commericial poultry flocks is essential in preventing outbreaks of AI.

The clinical signs in chickens and turkeys include severe respiratory signs, with excessively watery eyes and sinusitis, cyanosis (blueness due to lack of oxygen) of the combs, wattles, and shanks; edema of the head, ruffled feathers, diarrhea and nervous signs. The last eggs laid after the onset of illness frequently have no shells. In acute cases involving sudden death, clinical signs may not be seen. Mortality occurs as early as 24 hours after the first signs of disease, and frequently withing 48 hours, or can be delayed for as long as a week. Mortality rates of 100% have been reported.

Compiled from " Highly Pathogenic Avian Influenza (Fowl Plague) Factsheet", April 11, 1995, Agrilculture and Agri-Food Canada, Animal Health Division.

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Other Links:
Avian Influenza: Are You Prepared to Handle an Outbreak ? - Alberta Agriculture


Surveillance: Special Issue - Exotic Diseases, Vol 23, 1996
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 Veterinarians
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, C.M.
Merck & Co., Inc, Rahway, N.J., U.S.A., 1986, ISBN 911910-53-0