Global Transmission of Foot and Mouth Disease by Fomites

Definition: Fomite – any inanimate object via which pathogenic organisms may be transferred, although it does not support their growth.

  1. The transmission of Foot and Mouth Disease globally is primarily caused by the movement of cloven-hoofed animals or animal products infected with the virus from one country into another. Usually, live animals are involved - but meat products or byproducts (especially if fed to pigs) are known to play a major role. Airborne spread between close neighbouring countries (e.g. in Europe) may be a possibility.
  2. Although the spread of the FMD virus from farm to farm via contaminated fomites (boots, vehicles, containers, clothing etc) can occur locally there has never been a recorded or objectively documented case of the virus being spread globally by this method.
  3. For FMD to be introduced the fomite must have become contaminated with infected material, generally from the mouth or feet of an infected animal. It is also possible that virus shed onto the ground may adhere to footwear or clothing. Just being in the general area of an outbreak does not pose a risk.
  4. Below is a table indicating the survivability of the FMD virus on various materials under experimental conditions, where the FMD virus has been deliberately applied to the materials:
    Contaminated objects (Survival time in weeks)
    Soil (1-21)*
    Barn dirt; barn sand (1)
    Road sand; garden soil (1.5)
    Barns (brick, adobe, wood) (2-11)*
    Walls, brick and plaster (2)
    Hay (4)
    Wool, sheep (2)
    Hair, cattle (4)
    Glass surface (2+)
    Clothing and footwear ** (3-9)*
    (*) Ranges indicate European summer/winter survival times.
    (**) Cotton garments, leather shoes, rubber boots.
  5. Wool is considered a potential vehicle for transmitting FMD. If wool was harvested from animals in flocks with clinical disease (excreting large quantities of virus in saliva) it could harbour the FMD virus for up to several weeks at temperatures near freezing. Survival of the virus would be unlikely for more than a week or two if the wool were stored at temperature above 20°C. The temperature and humidity in a wool bale are quite stable during shipping. This risk is managed by requiring in the import health standard a minimum of four weeks between shearing and importation.
  6. Sunlight has little effect on the virus; environmental inactivation is related more to the effects of desiccation and temperature than to sunlight per se. However, there is a critical relative humidity range of 55-60% below which virus survival is poor.
  7. The FMD virus is susceptible to both acid and alkaline conditions and is most stable at pH7.4-7.6. It is rapidly inactivated below pH 4 (e.g. tomato juice) and above pH 11 (e.g. household bleach).
  8. The virus can withstand freezing. Winter survival periods for the virus are significantly longer than for the summer. The cold or freezing
    helps to preserve the virus (however it cannot replicate outside a living host).
  9. For fomites such as containers or used machinery carried by ship from the UK, the likelihood of the virus surviving the voyage is
    negligible due to the voyage time, the temperatures encountered and the effects of desiccation.
  10. Clothing or footwear being worn by passengers arriving in New Zealand is relatively low risk unless it has been on an infected property and has gross contamination.
  11. Summary
    • FMD can be transmitted via fomites such as footwear, vehicles, containers etc.
    • There is no documented case of international transmission except by cloven-hoofed animals and animal products (and perhaps wind).
    • The risk of containers, vehicles, footwear or clothing harbouring the virus exists, but requires the fomite to have had direct contact with the virus – ie. contact with infected animals or contact with areas where infected animals have recently been.
    • The virus is rapidly broken down by heat, low humidity and change in pH.
    • Cleaning inorganic fomites of visible contamination and then applying an approved disinfectant will deal with the virus.
    • Laundering of clothes will kill the virus.
    • The time taken (and the equatorial temperature) means that inorganic fomites arriving as sea cargo will not pose a risk.

Page last updated: 7 August 2008