Foot and Mouth Disease

FMD virus is a picornavirus which means it is part of the Picornaviridae family.  It is a non-enveloped, single positive stranded RNA virus.  The nucleocapsid is 60 protomers arranged in an iscosahedral form.  Each protomer is 4 polypeptides.  The RNA genome has a protein on the 5’ end that is a primer for transcription by RNA polymerase.  FMD virus is a member of the Apthovirus genus.  This genus infects many different types of vertebrates and has a larger genome than other picornaviruses.  FMD in particular has 8000 bases in its genome.   The nucleocapsid is 27-30 nm across.

           

There are 7 serotypes described of this disease.  Each serotype has different antigens as well as other characteristics, like transmissibility.  The serotypes are found in different parts of the world and are regionally spread.  The serotypes are O, A, C, SAT-1, SAT-2, SAT-3 and Asia-1, with O being the most common serotype.

 

The virus has very specific environmental preferences, such as a 4^oC temperature and a neutral pH.  Outside of the host, it is sensitive to heat, dessication, UV radiation and low pH. Direct exposure of the virus to temperature change or pH change can be lethal to the virus, however a virus that is that is unexposed to sunlight or is protected by tissue can survive for many days/weeks outside the body.  FMD virus can survive in lymph nodes and bone marrow post-death, whereas it will be destroyed in muscles after rigor mortis when the pH goes below 6.