Extension Ag Update
May/June 2001
Articles Research Resources Internet Links Ag Facts Education

Overview of Hoof and Mouth Disease (HMD)

Even though it has a low fatality rate, HMD is considered the world's most important animal disease. HMD affects all cloven-footed animals and is present in Africa, Asia, South America, and Europe. A good Web resource is found at http://aleffgroup.com/avisfmd/.

The current outbreak of the disease in the United Kingdom has brought considerable media attention. The previous most recent outbreak in the UK was in 1967-68. A devastating epidemic occurred in Taipei, China in 1997, when over four million pigs died or were slaughtered within two months. The last outbreak for the United States was 1929, in Canada was 1951-54, and in Mexico was 1946-54.

Horses are not susceptible to the disease. Humans are evidently slightly susceptible and may develop vesicles (or blisters) in the mouth or on hands. For more information: http://www.iah.bbsrc.ac.uk/virus/Picornaviridae/enterovirus/hfmd.htm. Cases of human infection are rare, even among people working with infected animals and materials.

The virus that causes HMD is easily and rapidly transmitted through air, infected meat and milk products, clothing, or other means by which the agent can be carried to the next host. It is estimated that sufficient virus to initiate an infection can be windborne as far as 150 miles. Pigs are the most potent excretors of airborne virus, and cattle the most susceptible to airborne infections. The virus has been found in the semen of bulls and boars, although transmission via embryos from infected cows has not been found to occur. Animals that have recovered from the disease can commonly continue to be carriers of the virus and remain infectious for as long as 6 months. The virus may persist for over one year on infected premises, for 12 weeks on clothing and feed, and for up to a month on hair.

The morbidity rate in outbreaks of HMD in susceptible animals can rapidly approach 100 percent, although the case fatality rate is generally less than two percent but slightly higher in younger animals. After an incubation period of one to seven days, animals quit eating, develop a fever of 104°F to 106°F, and develop vesicles--or fluid-filled blisters--on the oral mucosa and feet. The severity varies widely between the different viral strains. More severe reactions can include heart failure, enteritis, and ascending posterior paralysis.

Vaccination is common in the countries where the disease occurs. Clinical disease is reduced by vaccination, but carrier animals still occur and can, in fact, be produced by the vaccine. These carrier animals are a potent method of spreading the disease and also provide an excellent medium for the mutation of existing viral strains.

According to Dr. Richard Hull, Illinois State Veterinarian, the Illinois Department of Agriculture is requesting that, for 10 days after their arrival in the United States, persons who have been in designated endemic FMD countries not visit animal farms, sale barns, stockyards, animal laboratories, packing houses, zoos, exhibitions, and any other place where cattle, sheep, goats, deer and other ruminants, and swine may be present.

Under no circumstances should any meat or other animal products be brought into the United States - no matter how small or apparently safe. No clothing or footwear that was worn in the country experiencing FMD should be worn unless properly disinfected. The virus can be killed using a 0.1 percent concentration of household bleach (1ounce bleach/gal. of water). If the area to be disinfected is heavily soiled, a three percent solution should be used (2.5 ounces bleach/gal. of water). For further information about guidelines from the Illinois Department of Agriculture, contact Richard D. Hull, DVM, State Veterinarian, at dhull@agr.state.il.us.