Foot-and-mouth disease (FMD) or hoof-and-mouth disease (Aphtae epizooticae) is a highly contagious and sometimes fatal viral disease of cloven-hoofed animals, including domestic animals such as cattle, water buffalo, sheep, goats and pigs, as well as antelope, bison and other wild bovids, and deer.
In addition, hedgehogs and elephants are susceptible to the disease. The llama and alpaca may develop mild symptoms but are resistant to the disease and will not pass it on to others of the same species. In laboratory experiments, mice, rats and chicken have been successfully infected by artificial means, but it is not believed that they would contract the disease under natural conditions. Just as humans may spread the disease by carrying the germs on their clothes and body, animals that are not susceptible to the disease may still aid in spreading it. This was the case in Canada in 1952 when an outbreak flared up again after dogs had carried off bones from dead animals. Wolves are thought to play a similar role in the former Soviet Union.
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.
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.
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, and Uruguay and Argentina have not had an outbreak since 2001. North America, Australia and Japan have been free of FMD for many years. New Zealand has never had a case of foot and mouth disease. 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.
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.
Infection with foot-and-mouth disease tends to occur locally - that is, the virus is passed on to susceptible animals through direct contact with infected animals or with contaminated pens or vehicles used to transport livestock. The clothes and skin of animal handlers such as farmers, standing water, and uncooked food scraps and feed supplements containing infected animal products can harbor the virus as well. Cows can also catch FMD from the semen of infected bulls. Control measures include quarantine and destruction of infected livestock, and export bans for meat and other animal products to countries not infected with the disease.
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). When such a 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.
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 from 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.
Seven main types of Foot and Mouth Virus are believed to exist. Like other viruses, the FMD virus continually evolves and mutates, thus one of the difficulties in vaccinating against FMD is the huge variation between and even within serotypes. There is no cross-protection between serotypes (meaning that a vaccine for one serotype will not protect against any others) and in addition, two strains within a given serotype may have nucleotide sequences that differ by as much as 30% for a given gene. This means that FMD vaccines must be highly specific to the strain involved. Vaccination only provides temporary immunity that lasts from months to years.
Currently, the World Organisation for Animal Health recognizes countries to be in one of three disease states with regards to FMD: FMD present with or without vaccination, FMD-free with vaccination, and FMD-free without vaccination. Countries that are designated FMD-free without vaccination have the greatest access to export markets, and therefore many developed nations, including Canada, the United States, and the UK, work hard to maintain their current FMD-free without vaccination status.
There are several reasons cited for restricting export from countries using FMD vaccines. The most important is probably that routine blood tests, relying on antibodies, cannot distinguish between an infected and a vaccinated animal. This would severely hamper screening of animals used in export products, risking a spread of FMD to importing countries. A widespread preventive vaccination would also conceal the existence of the virus in a country. From there, it could potentially spread to countries without vaccine programs. Lastly, an animal that is infected shortly after being vaccinated can harbour and spread FMD without showing symptoms itself, hindering containment and culling of sick animals as a remedy.
Many early vaccines used dead samples of FMD virus to inoculate animals. However, those early vaccines sometimes caused real outbreaks. In the 1970s, scientists discovered that a vaccine could be made using only a single key protein from the virus. The task was to produce such quantities of the protein that could be used in the vaccination. On June 18, 1981, the U.S. government announced the creation of a vaccine targeted against FMD; this was the world's first genetically engineered vaccine.
The North American FMD Vaccine Bank is housed at the United States Department of Agriculture's (USDA) Foreign Animal Disease Diagnostic Laboratory (FADDL) at Plum Island Animal Disease Center. The Center, located off the coast of Long Island, NY, is the only place in the United States where scientists can conduct research and diagnostic work on highly contagious animal diseases such as FMD. Because of this limitation US companies working on FMD usually use facilities in other countries where such diseases are endemic.
The disease spread fast among swine herds in Taiwan, with 200-300 new farms being infected daily. Causes for this include the high swine density in the area with up to 6,500 hogs per square mile, feeding of pigs with untreated garbage and farm's proximity to slaughterhouses. Other systemic issues like lack of laboratory facilities, slow response and initial lack of a vaccination program contributed. It is also alleged that farmers intentionally introduced FMD to their flocks, because the payment offered to farmers for culled swine was at a time higher than the market value of the swine.
A complicating factor is the endemic spread of Swine vesicular disease (SVD) in Taiwan. The symptoms are indistinguishabe from FMD, which may have led to previous mis-diagnosing of FMD as SVD. Laboratory analysis was seldomly used for diagnosis and FMD may thus have gone unnoticed for some time in Taiwan.
The swine depopulation was a massive undertaking, with the military contributing substantial manpower. At peak capacity, 200,000 hogs per day were disposed of, mainly by electrocution. Carcasses was disposed of by burning and burial, but burning was avoided in water resource protection area. In April industrial incinerators were running around the clock to dispose of the carcasses.
Initially, 40,000 combined vaccines for the strains O1, A24 and Asia were available and administered to zoo animals and valuable breeding hogs. At the end of March, half a million new doses of vaccines for O1 and Asia1 were made available. On the 3rd of May, 13 million doses of O1 vaccine arrived, and both the March and May shipments were distributed free of charge. There was a danger of vaccination crews spreading the disease; therefore, trained farmers were allowed to administer the vaccine under veterinary supervision.
Taiwan had previously been the major exporter of pork to Japan and among the top 15 pork producers in the world in 1996. During the outbreak, over 3.8 million swine was destroyed at a cost of $6.9 billion USD. The Taiwanese pig industry was devastated as a result and the export market in ruins. In 2007, Taiwan was considered free of FMD, but were still conducting a vaccination program, which restricts the export of meat from Taiwan.
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 the 1967 outbreak. The same strain was used at the nearby Institute for Animal Health and Merial 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.
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