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FOOT AND MOUTH DISEASE

Note for Owners:

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your animal is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate.

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Description
Foot-and-mouth  (F&M) disease is an extremely contagious viral infection of cloven-hoofed animals. It is an acute disease with sudden onset and, as the name of the disease suggests,  it causes vesicular and ulcerative lesions that affect the mouth and feet. F&M disease is found in many countries of the world, but the following are usually free of the disease :

  • Australia and New Zealand
  • North America
  • Central America
  • Europe
It is of major economic importance because it causes high mortality in young animals, and loss of production in others.

Cause
The cause of F&M disease is an RNA virus of the genus Aphthovirus which is a member of the Family Picornovirus and there are 7 types of virus with main strains A, O (most common) and C (least common). In addition, these are subdivided into substrains : SAT 1, SAT 2 and SAT 3 and ASIA-I and others. Each strain may have different characteristics, affect different species in different ways, and be more or less virulent than other strains.

The outbreak of F&M Disease in Western Europe during February 2001 was caused by a serotype O virus (now called the PanAsia strain) which emerged initially on the Indian subcontinent in 1990. It subsequently spread across the Middle East and reached Turkey in 1996. In 2001 it reached the UK and France. In the East it had spread to China and Taiwan by 1999, and by March 2000 it had reached Korea (free of F&M disease since 1934) and Japan (free of F&M disease since 1908), Russia and Mongolia. It has also spread to South Africa (2000 - the first outbreak of type O F&M disease). It reached the UK (free since 1984) in February 2001 and France in March 2001..

A new Type A strain of F&M disease has also been reported recently by the United Nations. It emerged in Iran in 1996 and spread to Turkey by 1998.

The F&M disease virus is extremely resistant in the environment making eradication and control difficult. The virus :

  • can persist for over 1 year in infected premises
  • can persist for up to 3 months on clothing, or in feed
  • can persist for up to 1 month on hair
  • can survive at least 1 month in frozen bull semen
  • can survive meat storage - including freezing, pickling, salted meats, dried meats
  • is resistant to cold 
  • is resistant to most common disinfectants -except for the following which kill the virus within minutes
    • Sodium hydroxide (1-2%)
    • Formalin (1-2%)
    • Sodium carbonate (4%)

Infection with F&M virus is usually through eating contaminated food but aerosol spread has also been identified. In the UK the most common sources of infection gaining access to the country are reported to be :

  • Contaminated meat products fed to pigs as swill- 40%
  • Transported by birds - 16%
  • Contaminated meat - not swill - 9%
  • Unknown - but including aerosol spread from mainland Europe - 28%

Infected animals shed most virus when the vesicles rupture, and they rarely shed virus for more than 4 days afterwards, although the virus can persist on their coats, or in their environment.

A characteristic of this virus is that it undergoes a rapid mutation rate (1-8 nucleotides may change each replication cycle). This means that new strains may emerge at any time with different virulence and characteristics. Rather like Influenza in humans, this makes protection through vaccination a difficult challenge because adequate protection may not be provided against new strains.

Species Occurrence
The Foot-and-mouth virus is most important in domesticated  and  wild cloven-hoofed animals, notably cattle, pigs, goats, buffalo, and sheep. Other species can become infected including hedgehogs, rodents and wild ruminants eg deer and a mild form of the disease occurs rarely in humans. Young immature animals and animals in prime condition seem to be  more susceptible to the disease.

Other animals , such as horses, dog and cats , can act as carriers of the virus by transporting it on their feet/hair. F&M disease may also be transmitted by ticks and the virus can pass through the gastrointestinal tract of birds that have eaten contaminated food.

Signs

The typical, initial signs of Foot-and-mouth disease are :

  • High body temperature 104-106oF (40-41oC)
  • Inappetance
  • Depression
  • Poor condition
  • Poor production eg milk
  • Excess salivation
  • Vesicles in the mouth which rupture within a week leaving ulcers
  • Vesicles in the feet - in the cleft of the foot and around the coronet
  • Lameness
  • Vesicles on the teats
  • Abortions
  • Gastroenteritis (pigs)
  • Death - especially in young animals

In cattle that survive the acute infection a whole range of possible complications can occur including:

  • Anaemia
  • Dyspnoea
  • Diabetes mellitus
  • Overgrowth of hair coat

Complications
The virus is extremely resistant in the environment (see Cause above)

Diagnosis
Diagnosis can be confirmed by identifying the virus in blood, milk, saliva, faeces, semen or from the fluid  discharges from mouth or foot vesicles 

In the UK tissue or blood samples submitted to the Institute for Animal Health's Pirbright Laboratory can yield a positive result within 4 hours though some samples take longer to isolate..

Treatment
There is no specific treatment for Foot-and-mouth disease virus. 

There are vaccines available against Foot-and-mouth disease, and in countries where containment is difficult or impossible it is used, but there are some limitations regarding its use notably that protection may not be given against emerging new strains of the virus. The PanAsia strain of virus is known to have caused disease in at least 3 Dairy Farms in Saudi Arabia despite regular vaccination and tight health controls. 

Development of vaccines against new strains of the virus takes at least 4 months.

Prognosis
Individual animals may survive the infection, but production is affected. Many countries choose to contain the virus through a slaughter policy - destroying all infected and in-contact animals.

Long term problems

Because the virus can survive in the environment it is important to destroy all animal carcases, bedding and other in-contact materials by burning. It is usual practice to leave infected premises unstocked for at least 6 months.

As long as the movement of livestock across International Borders is allowed, and as long as the movement of meat from countries with endemic F&M disease virus infection is allowed, this disease will continue to represent a serious threat to agriculture.

 

Links

Further up to date  information about the Outbreak of F&M disease in the UK can be found at the Ministry of Agriculture, Fisheries and Food web site : www.maff.gov.uk/animalh/diseases/fmd/default.html

 

Updated October 2013