FMD is present in many countries of the world, except for North and Central America (north of Panama), Australia, New Zealand, Great Britain and Scandinavia. The European Union (EU) countries are generally free of FMD. FMD was last reported in 1929 in the U.S.A., 1952 in Canada, and 1954 in Mexico.
The disease is highly contagious and may spread over great distances with movement of infected or contaminated animals, products, objects, and people. Pigs are mainly infected by ingesting infected food. Waste feeding has been associated with outbreaks. Cattle are mainly infected by inhalation, often from pigs, which excrete large amounts of virus by respiratory aerosols and are considered highly important in disease spread. Large amounts of virus are excreted by infected animals before clinical signs are evident, and winds may spread the virus over long distances.
People can be infected through skin wounds or the oral mucosa by handling diseased stock, the virus in the laboratory, or by drinking infected milk, but not by eating meat from infected animals. The human infection is temporary and mild. FMD is not considered a public health problem.
The incubation period is 2-21 days (average 3-8) although virus is shed before clinical signs develop. The rate of infection (morbity) can reach 100%, however mortality can range from 5% (adults) to 75% (suckling pigs and sheep). Recovered cattle may be carriers for 18 to 24 months; sheep for 1 to 2 months. Pigs are not carriers.
Clinical signs in cattle are salivation, depression, anorexia and lameness caused by the presence or painful vesicles (blisters) in the skin of the lips, tongue, gums, nostrils, coronary bands, interdigital spaces and teats. Fever and decreased milk production usually precede the appearance of vesicles. The vesicles rupture, leaving large denuded areas which may become secondarily infected. In pigs, sheep and goats the clinical signs are similar but milder. Lameness is the predominant sign.
Because of the range of species affected, the high rate of infectivity, and the fact that virus is shed before clinical signs occur, FMD is one of the most feared reportable disease in North America. An outbreak of FMD would, (and has in the past) cost millions of dollars in lost production, loss of export markets, and loss of animals during eradication of the disease. The significance of many other reportable diseases is due to their resemblence to FMD and the importance of distinguishing between them at the earliest indications of an unusual disease outbreak.
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Surveillance: Special Issue - Exotic Diseases, Vol 23,
MAF Regulatory Authority, Ministry of Agriculture
P.O. Box 2526, Wellington, New Zealand
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W.B. Saunders Company Ltd., London, 1996 , ISBN 0-7020-1912-7
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