Bruger:Sakkura/Mund- og klovsyge
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Mund- og klovsyge (Latin: Aphtae epizooticae) er en meget smitsom og i visse tilfælde dødelig virussygdom, der rammer kvæg og grise. Virus kan også inficere rådyr, geder, får og andre hovdyr, såvel som elefanter, rotter og pindsvin. Mennesker rammes kun yderst sjældent.
I 1897 påviste Friedrich Loeffler for første gang at sygdommen skyldes en virus. Han filtrerede blod fra et inficeret dyr gennem et porcelænsfilter, og fandt at den opsamlede væske stadig kunne give sygdommen videre til raske dyr.
Mund- og klovsyge forekommer i store dele af verden, og selvom nogle lande har været skånet for sygdommen i nogen tid udgør sygdommens evne til at inficere mange arter og sprede sig hurtigt et internationalt problem. Efter anden verdenskrig var sygdommen spredt over det meste af verden. I 1996 var sygdommen stort set begrænset til Asien, Afrika og dele af Sydamerika;
as of August 2007, Chile is free,[1] and Uruguay and Argentina have not had an outbreak since April 1994.Skabelon:Fact 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.[2] Most European countries have been recognized as 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 cancellation of many sporting events and leisure activities such as the Isle of Man TT, and the postponing of the general election for a month. 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 epidemic was avoided in the Republic of Ireland, with just one case recorded in Proleek, Co. Louth. In August 2007, FMD was found in a farm in Surrey, England. All livestock were culled and a quarantine erected over the area.
There are seven different 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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[redigér] Symptoms
Foot-and-mouth 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. Though most animals eventually recover from FMD, the disease can lead to myocarditis (inflammation of the heart muscle) and death, especially in newborn animals. Some infected animals remain asymptomatic, that is, they do not suffer from or show signs of the disease; but they are carriers of FMD and can transmit it to others.
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 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). 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.
Humans can be infected with foot-and-mouth disease through contact with infected animals, but this is extremely rare. Because the virus that causes FMD is sensitive to stomach acid, it cannot spread to humans via consumption of infected meat. In the UK, the last confirmed human case occurred in 1967, 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.
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; this disease is caused by a different virus of the family Picornaviridae, namely, an Enterovirus called Coxsackie A virus.
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 epidemic, when large numbers of animals are destroyed and revenues from milk and meat production go down.
[redigér] Vaccination
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 won't 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, so many developed nations, including Canada, the United States, and the UK, work hard to maintain their current FMD free without vaccination status.
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 vaccine targeted against FMD, which 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 1.5 miles 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 exotic animal diseases such as FMD.
[redigér] 2001 UK foot-and-mouth outbreak
Skabelon:Main The outbreak of foot and mouth disease in the United Kingdom in the spring and summer of 2001 saw more than 2,000 cases of the disease in farms in most of the British countryside. Around seven million sheep and cattle were killed in an eventually successful attempt to halt the disease. Cumbria was the worst affected area of the country, with 843 cases. With the intention of controlling the spread of the disease, public rights of way across land were closed by order. This damaged the popularity of the Lake District as a tourist destination. By the time the disease was halted by October 2001, the crisis was estimated to have cost Britain £8bn ($16bn). The Sunday Express has speculated that the foot and mouth virus was released deliberately out of Porton Down bio-weapons facility and could have possibly been the source of the outbreak two months later [1].
[redigér] 2007 UK foot-and-mouth outbreak
Skabelon:Main An outbreak of foot-and-mouth disease in the United Kingdom was confirmed by the Department for Environment, Food and Rural Affairs, on 3 August 2007, at a farm located between Wyke and Flexford in Surrey England.[3][4] All livestock on the premises were culled on 4 August. A nationwide ban on the movement of cattle and pigs has been imposed, with a three kilometre protection zone currently in place around the affected farm and a further ten kilometre zone of cattle surveillance. Other potential cases are being investigated.[5]
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.[6] It is the same strain as used at the nearby Institute for Animal Health and Merial Animal Health Ltd at Pirbright, 2½ miles (4 km) away which was named as a possible source of infection.[7]
[redigér] Ethical issues
Outbreaks of foot-and-mouth disease have resulted in the slaughter of millions of animals, despite this being a frequently non-fatal disease. The destruction of animals is primarily to prevent the disease from spreading throughout herds intended for human consumption or producing milk. Due to international efforts to eradicate the disease, infection would also lead to trade bans being imposed on affected countries. Critics of current policies to cull infected herds argue that the financial imperative needs to be balanced against the killing of many animals, especially when a significant proportion of infected animals, most notably those producing milk, would recover from infection and live full lives.[8]
[redigér] See also
- Hand, foot and mouth disease (HFMD)
- Swine vesicular disease (SVD)
[redigér] Notes
- ↑ Skabelon:Cite paper
- ↑ http://www.biosecurity.govt.nz/pests-diseases/animals/foot-n-mouth/freedom-statement.htm, offical government press release, New Zealand's Freedom From Foot And Mouth Disease, Biosecurity New Zealand, accessdate = 2007-08-06
- ↑ "Foot and Mouth Disease confirmed in cattle, in Surrey", DEFRA, 2007-08-03. Hentet 2007-08-03.
- ↑ "Further farms tested for disease", BBC News, 2007-08-04. Hentet 2007-08-04.
- ↑ Miles Goslett. "Foot and mouth: new possible cases reported", The Daily Telegraph, 2007-08-03. Hentet 2007-08-04.
- ↑ "Results of Foot and Mouth Disease Strain in Surrey, extension of zones", DEFRA, 2007-08-04. Hentet 2007-08-04.
- ↑ "Foot-and-mouth strain identified", BBC News, 2007-08-04. Hentet 2007-08-04.
- ↑ [http://www.fmd.brass.cf.ac.uk/FMDthstampingout.html The UK Foot and Mouth Epidemic of 2001: A Research Resource ]
[redigér] References
- Levy, Jay A., Heinz Fraenkel-Conrat, and Robert A. Owens. "Picornaviridae." Chap. 2, section 2.2 in Virology. Englewood Cliffs, NJ: Prentice Hall, 1994.-
- A Manufactured Plague: The History Of Foot-and-mouth Disease In Britain (2004, ISBN 1-84407-080-8) by Abigail Wood, a veterinary researcher at the University of Manchester. [2]
- The Lab-On-Site Project has more information in Foot and Mouth Disease Virus.
- Intervet International has a site devoted to FMD detailing information about Control, Vaccination, Legal Issues, and Preparation [3].

