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.
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.