Foot-and-Mouth Disease (FMD) affects domesticated and wild, cloven-footed animals. It was first shown to be caused by a virus (FMDV) in 1897.
FMD occurs in many parts of the world and especially in developing countries and in Africa and Asia. Some countries have been FMD-free for many years. North America, most European countries, Australia, New Zealand and many island states are recognised as being FMD-free. The disease has almost been eradicated in South America and eradication is underway in China and India.OIE map of official FMD status
After infection with the virus, the incubation period usually lasts a few days but occasionally up to two weeks. Then there is a fever associated with general illness and in cows with a marked decline in milk production. Soon after, blisters appear on the feet and in the mouth. Blistering in the mouth may cause stringy or foamy saliva and drooling, while foot blisters may cause lameness. Blisters rupture to form erosions that heal over a period of weeks. Disease severity varies according to species, breed and pre-existing immunity. Subclinical infection is common in small ruminants.
Myocarditis is possible in young animals and this can be associated with sudden death.OIE Technical Disease Card for Foot-and-Mouth Disease
FMD is highly contagious and can be spread from animal to animal by close contact or by aerosols. Transmission can also occur via products including meat and milk from infected animals and through contact with contaminated objects (such as farm equipment, vehicles, clothes and feed).
There is no specific treatment for FMD but provision of adequate drinking water and prevention of mastitis and fly strike all improve recovery, especially for dairy cattle which can be severely affected by the disease.
Control may be possible by vaccination, animal movement control/quarantine and destruction of infected animals. Biosecurity and disinfection are also important in blocking spread. Vaccination is hampered by the antigenic diversity of the virus, the short-lived nature of protective immunity and the thermal instability of FMD vaccines.
Varieties and occurrence
There are at 7 different varieties (serotypes) of FMDV, named: Serotypes A, C, O, Asia1, SAT1, SAT2 and SAT3. All give rise to a similar disease.
The global distribution of these serotypes is not even:
- Serotypes A and O can be found in most FMD endemic regions, with the exception of southern Africa;
- The Asia1 serotype can be found in the FMD endemic regions of Asia;
- The African buffalo is the natural host for the South African Territory (SAT) serotypes. Serotpyes SAT1 and SAT2 can be found throughout Africa, while SAT3 is limited to southern and eastern Africa;
- FMDV serotype C has not been detected since 2004 (in Kenya and Brazil), so it is possible that this serotype is no longer circulating.
Genetic relationship (using VP1 sequences) between FMDV serotypes. The prototype strain sequences used to create this phylogenetic tree are available on www.wrlfmd.org