Foot-and-mouth disease

Foot-and-mouth disease is a contagious viral infection of cloven-footed domestic and wild mammals and humans. It is virulent and spreads extremely rapidly. An adult infected animal will usually recover, but usually with partial loss of health and loss of economic value (eg sterility).

The disease is caused by the viruses of the Picorna family; there are several known types. Cattle, hogs, sheep and goats are most frequently affected, in that order, though deer, camels, giraffes, hedgehogs, tapirs and elephants have also been found with the disease. Other animals such as dogs, rats, rabbits, guinea pigs, and mice have contracted the disease artificially under laboratory conditions but not naturally. Common carriers of the disease are earthworms and birds. The disease can be transmitted to man (but this is rare), by contagion and by wind. The most common means of infection is the ingestion of contaminated foodstuffs. The virus is shed in all excretions of sick animals including urine, faeces, saliva, milk and semen. This occurs before clinical evidence of the disease is present.

Foot and mouth disease is characterized by the formation of vesicles or blisters on the mucous membrane covering the various parts of the mouth, including the tongue, lips, gums, dental pad, and the palate. Vesicles are also found above the claws of the feet and on dew claws, muzzle and nostrils, also teats and udder of nursing cows. The blisters rupture leaving a raw surface which is prone to other infections. Symptoms include an increase in body temperature, loss of appetite, lassitude and profuse slobbering. Chewing is painful and the animal loses condition and weight, and often becomes lame. Milk flow drops or stops, abortion, mastitis and sterility may occur. Mortality in adult animals is usually less than 5% but is higher in young animals. In severe outbreaks mortality of 50% has been recorded, following severe inflammation and degeneration of the heart muscle.

First recorded outbreak in the USA: 1870, last: 1929. Last Australian outbreak: 1872. Confusion of symptoms with bovine vesicular disease resulted in unnecessary slaughter in the UK in Dec 1972.

It is generally considered enzootic, or frequently epizootic, in most of the major livestock producing countries of the world, except in North America, Central America, Australia and New Zealand. It is prevalent in many African game areas, also among affected wildlife species in any part of the world.

Incidence is higher during wet weather, as in the UK in 1967 and the winter of 2001.

In South America, the 1981-1982 biennium was one of the periods of the least recurrence of foot-and-mouth disease since the commencement of the national programmes for control of the disease. In 1982, recorded occurrences of the disease were the lowest, marking a decrease of 38% compared to 1981, 61% compared to the 1978-1980 triennium, and 75% compared to the 1976-1977 period.