Foot-and-mouth Disease - Vaccination

Vaccination

Like other viruses, the FMD virus continually evolves and mutates, thus one of the difficulties in vaccinating against it 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 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 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 status.

Reasons cited for restricting export from countries using FMD vaccines include, probably most importantly, routine blood tests relying on antibodies cannot distinguish between an infected and a vaccinated animal, which severely hampers 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 infected shortly after being vaccinated can harbor and spread FMD without showing symptoms itself, hindering containment and culling of sick animals as a remedy.

Many early vaccines used dead samples of FMDV to inoculate animals, but 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 enough quantities of the protein to be used in the vaccination. On June 18, 1981, the US government announced the creation of a vaccine targeted against FMD, the world's first genetically engineered vaccine.

The North American FMD Vaccine Bank is housed at the United States Department of Agriculture's Foreign Animal Disease Diagnostic Laboratory at Plum Island Animal Disease Center. The Center, located 1.5 miles (2.4 km) 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.