Foot-and-mouth disease

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Foot-and-mouth disease (FMD, Latin binomial Aphtae epizooticae) is a highly contagious and sometimes fatal viral disease of cattle and pigs. It can also infect deer, goats, sheep, and other bovids with cloven hooves, as well as elephants, rats, and hedgehogs. Humans are very rarely affected. Foot-and-mouth disease virus (FMDV) is the prototypic member of the Aphthovirus genus in the Picornaviridae family. This picornavirus is the etiological agent of the acute systemic vesicular disease that affects cattle and other animals worldwide. It is a highly variable and transmissible virus.^[1]

The cause of FMD was first shown to be viral in 1897 by Friedrich Loeffler. He passed the blood of an infected animal through a fine porcelain filter and found that the fluid that was collected could still cause the disease in healthy animals.

When FMD virus comes in contact with a host cell, it binds to a receptor site and triggers a folding-in of the cell membrane. Once the virus is inside the host cell, its protein coat dissolves. New viral RNA and components of the protein coat are then synthesized in large quantities and assembled to form new viruses. After assembly, the host cell lyses (bursts) and releases the new viruses.

Foot-and-mouth disease is caused by FMDV, an Aphthovirus of the viral family Picornaviridae. The members of this family are small (25-30 nm), nonenveloped icosahedral viruses that contain single-stranded RNA (ribonucleic acid, the viral genetic material). There are seven FMD serotypes: O, A, C, SAT-1, SAT-2, SAT-3, and Asia-1. These serotypes show some regionality, and the O serotype is most common.

FMD occurs throughout much of the world, and whilst some countries have been free of FMD for some time, its wide host range and rapid spread represent cause for international concern.

The average incubation period of the Foot and Mouth virus varies but is generally around 3-8 days.^[2] The disease is characterized by high fever that declines rapidly after two or three days; blisters inside the mouth that lead to excessive secretion of stringy or foamy saliva and to drooling; and blisters on the feet that may rupture and cause lameness. Adult animals may suffer weight loss from which they do not recover for several months as well as swelling in the testicles of mature males, and in cows, milk production can decline significantly.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

The cause of FMD was first shown to be viral in 1897 by Friedrich Loeffler. He passed the blood of an infected animal through a fine porcelain filter and found that the fluid that was collected could still cause the disease in healthy animals.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

When FMD virus comes in contact with a host cell, it binds to a receptor site and triggers a folding-in of the cell membrane. Once the virus is inside the host cell, its protein coat dissolves. New viral RNA and components of the protein coat are then synthesized in large quantities and assembled to form new viruses. After assembly, the host cell lyses(bursts) and releases the new viruses.

Humans can be infected with foot-and-mouth disease through contact with infected animals, but this is extremely rare. Some cases were caused by laboratory accidents. Because the virus that causes FMD is sensitive to stomach acid, it cannot spread to humans via consumption of infected meat, except in the mouth before the meat is swallowed. In the UK, the last confirmed human case occurred in 1966^[1][2], and only a few other cases have been recorded in countries of continental Europe, Africa, and South America. Symptoms of FMD in humans include malaise, fever, vomiting, red ulcerative lesions (surface-eroding damaged spots) of the oral tissues, and sometimes vesicular lesions (small blisters) of the skin. According to a newspaper report Foot and Mouth disease killed two children in England in 1884, suspectedly due to infected milk.^[3]

There is another viral disease with similar symptoms, commonly referred to as “hand, foot and mouth disease“, that occurs more frequently in humans, especially in young children; the cause, Coxsackie A virus, is different to FMDV. Both are members of the Picornaviridae family, but while FMDV belongs to the Aphthovirus genus, Coxsackie viruses belong to the Enteroviruses.

Because FMD rarely infects humans but spreads rapidly among animals, it is a much greater threat to the agriculture industry than to human health. Farmers around the world can lose huge amounts of money during a foot-and-mouth epizootic, when large numbers of animals are destroyed and revenues from milk and meat production go down.

Soon after infection, the single stranded positive RNA that constitutes the viral genome is efficiently translated using a cap-independent mechanism driven by the internal ribosome entry site element (IRES). This process occurs concomitantly with the inhibition of cellular protein synthesis, caused by the expression of viral proteases. Processing of the viral polyprotein is achieved cotranslationally by viral encoded proteases, giving rise to the different mature viral proteins. Viral RNA as well as viral proteins interact with different components of the host cell, acting as key determinants of viral pathogenesis. In depth knowledge of the molecular basis of the viral cycle is needed to control viral pathogenesis and disease spreading.^[4]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Foot-and-mouth disease is caused by FMDV, an Aphthovirus of the viral family Picornaviridae. The members of this family are small (25-30 nm), nonenveloped icosahedral viruses that contain single-stranded RNA (ribonucleic acid, the viral genetic material). There are seven FMD serotypes: O, A, C, SAT-1, SAT-2, SAT-3, and Asia-1. These serotypes show some regionality, and the O serotype is most common.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

FMD occurs throughout much of the world, and whilst some countries have been free of FMD for some time, its wide host range and rapid spread represent cause for international concern.

FMD occurs throughout much of the world, and whilst some countries have been free of FMD for some time, its wide host range and rapid spread represent cause for international concern. After World War II, the disease was widely distributed throughout the world. In 1996, endemic areas included Asia, Africa, and parts of South America; as of August 2007, Chile is disease free,^[1] and Uruguay and Argentina have not had an outbreak since April 1994. North America, Australia and Japanhave been free of FMD for many years. New Zealand has never had a case of foot and mouth disease.^[2] Most European countries have been recognized as disease free, and countries belonging to the European Union have stopped FMD vaccination.

However, in 2001, a serious outbreak of FMD in Britain resulted in the slaughter of many animals, the postponing of the general election for a month, and the cancellation of many sporting events and leisure activities such as the Isle of Man TT. Due to strict government policies on sale of livestock, disinfection of all persons leaving and entering farms and the cancellation of large events likely to be attended by farmers, a potentially economically disastrous epizootic was avoided in the Republic of Ireland, with just one case recorded in Proleek, Co. Louth. In August 2007, FMD was found at two farms in Surrey, England. All livestock were culled and a quarantine erected over the area. There have since been two other suspected outbreaks, although these seem now not to be related to FMD.

The outbreak of foot-and-mouth disease in the United Kingdom in the spring and summer of 2001 was caused by the “Type O pan Asia” strain of the disease^[3]. This episode saw more than 2,000 cases of the disease in farms throughout the British countryside. Around seven million sheep and cattle were killed in an eventually successful attempt to halt the disease. The county of Cumbria was the worst affected area of the country, with 843 cases. By the time the disease was halted by October 2001, the crisis was estimated to have cost Britain £8bn ($16bn) in costs to the agricultural and agricultural support industries and to the outdoor industry. The major reason this outbreak was so serious was the time between infection being present at the first outbreak loci and the time that countermeasures were put into operation against the disease such as transport bans and detergent washing of both vehicles and personnel entering livestock areas.

An outbreak of foot-and-mouth disease in the United Kingdom was confirmed by the Department for Environment, Food and Rural Affairs, on 3 August2007, on farmland located in Normandy, Surrey.^[4][5] All livestock in the vicinity were culled on 4 August. A nationwide ban on the movement of cattle and pigs was imposed, with a 3 km (1.9 mile) protection zone placed around the outbreak sites and the nearby virus research and vaccine production establishments, together with a 10 km (6.2 mile) increased surveillance zone.^[6]

On 4 August the strain of the virus was identified as an “01 BFS67-like” virus, one linked to vaccines and not normally found in animals, and isolated in the1967 outbreak.^[7] The same strain was used at the nearby Institute for Animal Health andMerial Animal Health Ltd at Pirbright, 2½ miles (4 km) away which is an American/French owned research facility, and was identified as a possible source of infection.^[8]

On 12 September a new outbreak of the disease was confirmed in Egham, Surrey, 19km (12 miles) away from the original outbreak^[9], with a second case being confirmed on a nearby farm on 14 September.^[10]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Though most animals eventually recover from FMD, the disease can lead to myocarditis (inflammation of the heart muscle) and death, especially in newborn animals.

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