African Swine Fever


African Swine Fever (ASF) is a highly contagious, generalized disease of pigs caused by an Iridovirus that exhibits varying virulence between strains, although different serotypes cannot be identified. The virus resists inactivation, and can persist in meat up to 15 weeks, processed hams up to 6 months and up to one month in contaminated pens. It is endemic in most of Southern Africa, and on the Iberian peninsula of Europe. Since the 1960's, outbreaks have occurred in France, Italy, Malta, Belgium,Holland, Cuba, Domican Republic and Haiti.

In Africa, warthogs and their associated ticks (Ornithodoros moubata porcinus) are the reservoir of disease, although the infection is not clinical in warthogs. Outbreaks occur when domestic pigs come in contact with the ticks, rather than from direct transmission from other pigs or warthogs. In Europe, direct transmission is more important as the virus is shed in high concentration in excretions and secretions during the acute phase. Ticks (Ornithodoros erraticus) on the Iberian peninsula can also be a source of infection.

Recovered pigs may remain chronically infected and excrete the virus for 6 weeks after infection. Contaminated pens and garbage feeding with material from international airports or seaports are documented methods of spread due to the resistance of the virus to inactivation.

After an incubation period of 5-15 days, the disease may manifest itself in a number of forms:

African Swine Fever is clinically, and on post mortem, very similar to Hog Cholera, which in parts of Europe is referred to as "Swine Fever" or "Classical Swine Fever". Laboratory tests, such as direct flourescent antibody on suspected tissues, are required to differentiate the two diseases.

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References:

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

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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

Veterinary Medicine - Eighth Edition
Radositis, O.M., Blood, D.C., and Gay, C.C.
Balliere Tindal, London, U.K., 1994, ISBN 0 7020 1592 X