Foot-and-mouth disease (FMD) is a highly contagious, acute disease of cloven-hoofed, domesticated and wild animals. The disease is characterized by fever, lameness and the appearance of vesicles (fluid-filled blisters) on the feet and in, or around, the mouth. It is much feared as it can spread extremely rapidly and has the potential to cause enormous economic losses. Hence, FMD is the single most important constraint to international trade in livestock and animal products. The disease is caused by foot-and-mouth disease virus (FMDV). To multiply, the virus has to enter cells. Within a single infected cell, virus replication is completed within a few hours and can result in the release of over 100,000 new virus particles.
FMD is endemic in many countries of the world and also represents a major threat to countries that are normally free. The virus is categorised into seven serotypes, named A, O, C, Asia 1, and Southern African Territories (SAT) 1, 2 and 3. Identification of the appropriate serotype causing an outbreak is critical for the selection of effective vaccines.
At Lindholm, studies on FMD include the development and maintenance of rapid, sensitive and specific diagnostic methods for the identification of FMDV from infected animals. In addition serology is used as a screen for evidence of previous infections. Furthermore, studies on the molecular biology of the virus provide information concerning novel targets for interventions to combat the disease. Work is also performed in collaboration with countries which have endemic FMD, e.g. Pakistan & Uganda, to determine which FMD viruses are circulating and to provide information on appropriate vaccine strains. Replicating FMDV populations spontaneously generate virus variants. Molecular epidemiology utilizes the diversity within the virus, as determined by sequence analysis, to determine the source of new outbreaks.
A feature of FMD is that following an acute infection a high proportion of animals can remain infected for a long period of time (months or even years in some species). Such animals are termed carriers. The role of carriers in initiating new outbreaks is controversial but is greatly feared. The mechanism of virus persistence is not yet understood but is being analysed.
Control of the disease in countries in which it is sporadic or endemic is based mainly on routine prophylactic vaccination. Current FMD vaccines contain one or more strains of chemically-inactivated FMDV antigen but these vaccines give relatively short-term protection, e.g. for around 6 months. Studies at Lindholm, in collaboration with other centres around the world, are aimed at improving the current vaccines to improve stabilty, to reduce the risks from their production and to give long lasting protection.
Contact Anette Bøtner