Foot/Hoof and Mouth Disease

Foot and Mouth / Hoof and Mouth Disease

The name foot and mouth disease is a misnomer since the animals this disease affects technically do not have feet.
Hoof and Mouth Disease (HMD) is an acute infectious viral disease that affects cattle, sheep, pigs, goats and a variety of other domestic and wild animals as well as elephants, hedgehogs and rats. Also susceptible are any wild split or cloven-hoofed animals and yes, it can indeed be carried and spread by dogs and cats. Horses are not susceptible to the disease.

Livestock animals in this country are highly susceptible to HMD viruses. If an outbreak occurred in the United States, this could spread rapidly to all sections of the county by routine livestock movements unless it was detected early and eradicated immediately. HMD is one animal disease that livestock owners dread most because it has clinical as well as grave economic consequences.

The disease does not affect human safety and is extremely rare, but can occur in association with direct contact with infected tissue, animals, materials, and may develop into vesicles (blisters) in the mouth or on the hands. People, however, can spread the virus to animals. HMD can remain in human nasal passages for as long as 28 hours and can be carried on soiled footwear, clothing and other items for several days. Humans are susceptible to a related enterovirus that causes hand, foot and mouth disease (HFMD).

The disease is caused by any of several serotypes of the Picornaviridae/Aphthovirus family. The seven most common serotypes, called A, O, C, Asia1, SAT-1, SAT-2, and SAT-3, and each contain about 60 subtypes. Immunity to one type does not protect an animal against other types.

In the past year, FMD outbreaks have been reported in Russia, China, South Korea, Taiwan, Japan, Mongolia, and at least seven African and five South American countries. The disease is endemic in parts of Africa, Asia, the Middle East and South America. North and Central America, Australia, New Zealand, and Japan are free of infection. The last outbreak of HMD in the United States was in 1929, when the last of nine outbreaks were eradicated. A devastating epidemic occurred in Taipei, China, in 1997, when over 4 million pigs died or were slaughtered within two months. The previous most recent outbreak in the UK was in 1967-68. In Canada it was 1951-54, and in 1946-54 it was Mexico.

How is HMD Spread?

HMD is one of the most contagious of all animal diseases. The disease can spread quickly through a herd of animals via direct contact, through inhalation, ingestion, and reproduction. Under certain climatic conditions the virus can be airborne and is estimated that sufficient virus may spread over a large area to initiate an infection as far as 150 miles. The virus can also 'hitchhike' a ride on farm vehicles, equipment, people, products and can spread easily when an infected animal is moved to an uninfected herd. 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 30 days on hair.

Clinical Signs
The differential diagnosis of suspicious conditions should include:

1. Cattle -Vesicular stomatitis, bluetongue, infectious bovine rhinotracheitis, malignant catarrhal fever, bovine virus diarrhea/mucosal disease complex, mycotic stomatitis, foot rot, and rinderpest.
2. Swine -Vesicular stomatitis and swine vesicular disease.
3. Sheep - Bluetongue, sheep pox, contagious ecthyma, and ergot poisoning.
4. Goats - Goat pox and contagious ecthyma.

Initial signs are dullness, inappetance, decreased milk production, and fever, followed by an increased salivation, lameness, and serous nasal discharge. Smacking of the lips, drooling, and increased nasal discharge follows the appearance of early vesicles on the epithelium. Vesicles discharge either clear or cloudy fluid and may appear on the mouth, nares, muzzle, snout, interdigital space, coronary band, teats, and rumen papillae. Often blisters may not be observed because they rupture in time but will leave eroded areas surrounded by ragged fragments of loose tissue. As the blisters increase in size and number, soreness of the hooves leads to treading and kicking, and lesions become readily apparent. Lesions on the hard palate are seldom seen as vesicles but appear first as erosions. All food is refused if the mouth is severely involved, and severe hoof involvement may lead to reluctance to rise or refusal to move. Lactating cows may develop vesicles on the teats. Abortions have been observed in early pregnancy and calves with few visible lesions may die suddenly. Oral lesions in all species tend to heal quickly unless secondary bacterial infection supervenes. Hoof lesions take longer to heal, and hoof rot may develop and lead to extended lameness and sometimes abnormalities of the hoof. Mastitis, post-abortion retained placenta, and uterine infection are also seen.

The virus can also cause degeneration of heart muscle, which may result in sudden death of the host. The virus can be found in all parts of the body during the viremic stage of the infection. The virus is present in the saliva, exhaled air, ordure and essentially some virus can also occur in milk of diseased animals. Such animals also generate infectious aerosols. Any of these can be a source of infection to other stock. The virus can survive in infected animals for a long time, even after the animal is dead. The HMD virus can survive for quite a while in meat if the pH does not fall below 6.2. It can also survive in frozen, salted and cured meats, and in non-pasteurised dairy products.

Disinfectants that have been demonstrated to be effective against HMD:

Lye (sodium hydroxide) – 2 percent solution. Mix a 13-ounce can of lye in five gallons of water.
Soda ash (sodium carbonate) – 4 percent solution. Mix one pound soda ash in three gallons of water.
Citric acid - 0.2 percent solution.
Vinegar (acetic acid) - 2 percent solution. Mix one gallon of vinegar (4 percent) in a gallon of water.
Virkon S (Antec International) at a 1:200 dilution.
Household bleach (sodium hypochlorite) using a 0.1 percent concentration of household bleach (1ounce bleach/gal. of water). If the area to be disinfected is heavily soiled, a 3 percent solution should be used (2.5 ounces bleach/gal. of water).

Treatment

There is no known treatment for HMD. The United States subscribes to the eradication program that requires that all infected or exposed susceptible animals are killed and the carcasses buried or burned. Animal holding areas are then cleaned and disinfected and, after an appropriate waiting period, repopulated with a few susceptible, naive animals to determine the efficacy of the disinfecting procedure. All of the above procedures are performed under the direction of the Department of Agriculture. The Emergency Programs Staff of the Animal and of the Plant Health Inspection Service is specially trained to handle such situations.

One company has developed a peptide-based test that can simplify the diagnosis of HMD. The same company has developed a synthetic peptide-based HMD vaccine. The efficacy of the vaccine is now being studied. Early indications are that the vaccine can neutralize multiple serotypes of the virus.

In 2001, More than 2000 Confirmed Cases in GB. Throughout the UK the skies are dark with smoke from mountains of burning carcasses. The problem is so great that the British Army has been called in to help.