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
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
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 firstname.lastname@example.org.