Foot and mouth disease

• Cause: foot-and-mouth disease (FMD) is a highly contagious, transboundary viral disease of cloven-hooved mammals caused by FMD virus (FMDV).
• Signs:
  • General clinical signs include: short-lived pyrexia which precedes the development of gross clinical signs such as excessive salivation/nasal discharge, and the formation of vesicles on the oral mucosa (tongue, dental pad, gums), nostrils, teats, the inter-digital spaces and coronary bands of the feet.
  • However, the severity of clinical signs varies with the strain of the virus, exposure dose, age and breed of animal, host species, and level of host immunity.
• Diagnosis:
  • FMD can be suspected on appearance of clinical signs, however, definitive diagnosis cannot confirmed without further laboratory tests.
  • Diseases, such as vesicular stomatitis (VS) present with the same clinical signs in cattle.  
• Treatment:
  • Vaccines do exist for FMD and are used prophylactically in some areas of the world.
  • Vaccines will be ineffective if the animal is already infected.
  • There is no commercially available treatment which can specifically target FMDV once an animal is infected but supportive care including painkillers and antibacterials can be used for severe infection and secondary bacterial infection respectively.
  • Animals usually recover from clinical signs after clearance of the virus within about two weeks. Return to previous milk production can have a lag phase depending on breed.
• Prognosis: high morbidity (up to 100%), low mortality in adult animals (1-5%) but is observed in young animals due to myocarditis.

Geographic incidence

• Historically, FMD has occurred in most livestock containing areas of the world. However current global circulation of FMD tends to mirror economic development and is maintained within three continental epidemiological clusters within Asia, Africa and parts of South America.
• FMD has large economic impacts in endemic countries, where approximately three-quarters of the world’s livestock population reside.
• There are seven distinct serotypes of FMDV; O, A, C, Asia 1, and Southern African Territories (SAT) 1, 2 and 3. Although serotype C is currently believed to have disappeared having not been isolated since 2004.
• FMD serotypes are not evenly distributed around the world, and there is a tendency for genetically related viruses within a serotype to appear in the same geographical area, for reasons such as animal movement and trade patterns, physical barriers and immune pressures.
• Globally, the distribution of FMDV is divided into seven “geographic” pools, based on nucleotide sequence analyses.
  • Pool 1 – East Asia (serotypes O, A, and Asia 1).
  • Pool 2 – Central Asia (serotypes O, A, and Asia 1).
  • Pool 3 - Europe and West Asia (serotypes O, A, and Asia 1).
  • Pool 4 – East Africa (serotypes O, A, SAT 1, 2 (limited evidence for SAT 3)).
  • Pool 5 – West Africa (serotypes O, A, SAT 1 and 2).
  • Pool 6 – Southern Africa (serotypes SAT 1, 2 and 3).
  • Pool 7 - South America (serotypes O and A).
• However, within each serotype, different subtypes exist in the respective areas. Incursions of new serotypes and/or subtypes between epidemiological pools does occur which can lead to major outbreaks.
• FMD can occur sporadically in typically FMD free areas.

Age predisposition

• No age predisposition but risk of infection is related to immune status.

Breed/Species predisposition

• When looking at all species, in an area, clinical signs are most apparent in cattle followed by intensively reared pigs.
• Sheep, goats and other small ruminants usually present with transitory mild symptoms which can easily be confused with other conditions such as footrot Footrot, bluetongue Bluetongue and orf.

Public health considerations

• FMD is not defined as a zoonotic pathogen, however anecdotal evidence suggests in rare cases people who have either drunk milk from infected animals or have been in close proximity may develop mild cold like symptoms, with or without the development of blisters in the mouth.
• FMD is highly contagious to cloven hooved mammals and can be mechanically transmitted (eg via contaminated equipment/feed etc). It is essential therefore for farmers to maintain stringent biosecurity practices Biosecurity to prevent spread of the disease.

Cost considerations

• FMD is a disease of great economic importance.
• FMD costs are typically due losses such as:
  • Reduced milk production.
  • Loss of young vulnerable animals.
  • Abortions (as a result of pyrexia).
  • Vaccination.
  • Movement restrictions.
  • International trade restrictions.
• Consequences of an outbreak in a normally disease-free country, can be high. Knight-Jones & Rushton suggest that outbreaks in FMD free countries and zones can result in losses of over US $1.5 billion per year.
• It is estimated that the annual global impact of FMD in endemic regions is between US $6.5 and 21 billion. These countries also pose a significant threat to disease-free countries.