Foot-and-mouth disease: A disease caused by a highly infectious virus that can infect people but affects them most by infecting livestock -- cattle, pigs, sheep and goats. The foot-and-mouth disease virus (FMDV) is in the same family of viruses as those causing the common cold.
The virus is spread by many routes -- by contact with infected animals; by people exposed to the virus who develop no symptoms or just skin lesions but who harbor and spread FMDV; by items as varied as shoes, clothing, vehicles, farm implements, meat, milk and garbage that are contaminated with the virus; and by air. The virus incubates for from 2 days to over 2 weeks before an animal begins to show signs of the disease.
Cattle develop fever and blisters in their mouths, lose their appetites, lose weight and produce less milk. Pigs develop severe foot sores that make it impossible for them to walk. In sheep and goats, the foot problems are less obvious and may allow them to spread the infection. In all species, adult animals typically recover within two weeks, but death rates among young animals can be high. The many other susceptible animals include rats, deer and even elephants.
The available vaccines are directed against some of the serotypes (varieties) of the virus are ineffective because they induce immunity for only 6 months or so and vaccinated animals can become carriers of the virus even if they do not become sick. Vaccinated cattle who come in contact with the virus may harbor infectious virus in their mouths and throats for up to 30 months, and vaccinated sheep can become similar viral vectors for 9 months.
The disease is endemic in parts of Asia, Africa, the Middle East and South America. In 2001 the disease spread through farms in Britain, leading to quarantines, the mass slaughter of animals and agricultural damages amounting to an estimated $4.4 billion. The last large-scale outbreak of foot-and-mouth in the US occurred in the 1920's. Neither Canada nor Mexico has had an outbreak since the 1950's. But a single case would instantly shut down the export of all animal products.