Foot and Mouth Disease
Foot and mouth disease
Foot-and-mouth disease (FMD), also called hoof-and-mouth disease, is a highly contagious and economically devastating viral disease of cattle, swine, and other cloven-hoofed (split-toed) ruminants, including sheep, goats, and deer. The disease is highly contagious, for nearly 100% of exposed animals become infected, and it spreads rapidly through susceptible populations. Although there is no cure for FMD, it is seldom fatal, but it can kill very young animals.
The initial symptoms of the disease include fever and blister-like lesions (vesicles). The vesicles rupture into erosions on the tongue, in the mouth, on the teats, and between the hooves. Vesicles that rupture discharge clear or cloudy fluid and leave raw, eroded areas with ragged fragments of loose tissue. Erosions in the mouth result in excessive production of sticky, foamy, stringy saliva, which is a characteristic of FMD. Another characteristic symptom is lameness with reluctance to move. Other possible symptoms and effects of FMD include elevated temperatures in the early stages of the disease for two to three days, abortion, low conception rates, rapid weight loss, and drop in milk production. FMD lasts for two to three weeks, with most animals recovering within six months. However, it can leave some animals debilitated, thus causing severe losses in the production of meat and milk. Even cows that have recovered seldom produce milk at their original rates. Animals grown for meat do not usually regain lost weight for many months. FMD can also lead to myocarditis, which is an inflammation of the muscular walls of the heart, and death, especially in newborn animals. Infected animals can spread the disease throughout their lives so the only way to stop an outbreak is to destroy the animals.
The virus that causes the disease survives in lymph nodes and bone marrow at neutral pH . There are at least seven types and many subtypes of the FMD virus. The virus persists in contaminated fodder and in the environment for up to one month, depending on the temperature and pH. FMD thrives in dark, damp places, like barns, and can be destroyed with heat, sunlight, and disinfectants.
The disease is not likely to affect humans, either directly or indirectly through eating meat from an infected animal, but humans can spread the virus to animals. FMD can remain in human nasal passages for at up to 28 hours. FMD viruses can be spread by other animals and materials to susceptible animals. The viruses can also be carried for several miles on the wind if environmental conditions are appropriate for virus survival. Specifically, an outbreak can occur when:
- people wearing contaminated clothes or footwear or using contaminated equipment pass the virus to susceptible animals
- animals carrying the virus are introduced into susceptible herds
- contaminated facilities are used to hold susceptible animals
- contaminated vehicles are used to move susceptible animals
- raw or improperly cooked garbage containing infected meat or animal products is fed to susceptible animals
- susceptible animals are exposed to contaminated hay, feed-stuffs, or hides
- susceptible animals drink contaminated water
- a susceptible cow is inseminated by semen from an infected bull
Widespread throughout the world, FMD has been identified in Africa, South America, Middle East, Asia, and parts of Europe. North America, Central America, Australia , New Zealand, Chile, and some European countries are considered to be free of FMD. The United States has been free of FMD since 1929, when the last of nine outbreaks that occurred during the nineteenth and early twentieth centuries was eradicated.
In 2001, an FMD outbreak was confirmed in the United Kingdom, France, the Netherlands, the Republic of Ireland, Argentina, and Uruguay. Officials in the United Kingdom detected 2,030 cases of FMD, slaughtered almost four million animals, and took seven months to control the outbreak. The economic losses were estimated to be in the billions of pounds, and tourism in the affected countries was adversely affected. The outbreak was detected on February 20, 2001; no new cases were reported after September 30, 2001; on January 15, 2002, the British government declared the FMD outbreak to be over. The outbreak appeared to have started in a pig finishing unit in Northumberland, which was licensed to feed processed waste food. The disease appeared to have spread through two routes: through infected pigs who were sent to a slaughterhouse and through windborne spread to sheep on a nearby farm. These sheep entered the marketing chain and were sold in markets and through dealers, where they infected other sheep, people, and vehicles, spreading the FMD virus throughout England, Wales, southern Scotland. As the outbreak continued, cases were detected in other European countries.
The Animal and Plant Health Inspection Service (APHIS) of the United States Department of Agriculture (USDA) has developed a on-going comprehensive prevention program to protect American agriculture from FMD. APHIS continuously monitors for FMD cases worldwide. When FMD outbreaks are identified, APHIS initiates regulations that prohibit importation of live ruminants and swine and many animal products from the affected countries. In the 2001 outbreak in some European Union member countries, APHIS temporarily restricted importation of live ruminants and swine and their products from all European Union member states. APHIS officials are on duty at all United States land and maritime ports-of-entry to ensure that passengers, luggage, cargo, and mail are checked for prohibited agricultural products or other materials that could carry FMD. The USDA Beagle Brigade, dogs trained to sniff out prohibited meat products and other contraband items, are also on duty at airports to check incoming flights and passengers.
The cooperation of private citizens is a crucial component of the protection program. APHIS prevents travelers entering the United States from bringing any agricultural products that could spread FMD and other harmful agricultural pests and diseases. Therefore passengers must declare all food items and other materials of plant or animal origin that they are carrying. Prohibited agricultural products that are found are confiscated and destroyed. Passengers must also report any visits to farms or livestock facilities. Failure to declare any items may result in delays and fines up to $1,000. Individuals traveling from countries that have been designated as FMD-affected must have shoes disinfected if they have visited farms, ranches, or other high risk areas, such as zoos, circuses, fairs, and other facilities and events where livestock and animals are exhibited.
APHIS recommends that travelers should shower and shampoo prior to and again after returning to the United States from an FMD-affected country. They should also launder or dry clean clothes before returning to the United States. Full-strength vinegar can be used by passengers to disinfect glasses, jewelry, watches, belts, hats, cell phones, hearing aids, camera bags, backpacks, and purses. If travelers had visited a farm or had any contact with livestock on their trip, they should avoid contact with livestock, zoo animals, or wildlife for five days after their return. Although dogs and cats cannot become infected with FMD, their feet, fur, and bedding should be cleaned of excessive dirt or mud. Pet bedding should not contain straw, hay, or other plant materials. The pet should be bathed as soon as it reaches its final destination and be kept away from all livestock for at least five days after entering the United States.
In the United States, animal producers and private veterinarians also monitor domestic livestock for symptoms of FMD. Their surveillance activities are supplemented with the work of 450 specially trained animal disease diagnosticians from federal, state, and military agencies. These diagnosticians are responsible for collecting and analyzing samples from animals suspected of FMD infection. If an outbreak were confirmed, APHIS would quickly try to identify infected and exposed animals, establish and maintain quarantines, destroy all infected and exposed animals using humane euthanization procedures as quickly as possible, and dispose of the carcasses by an approved method such as incineration or burial. After cleaning and disaffection of facilities where the infected animals were housed, the facility would be left vacant for several weeks. After this period, a few susceptible animals would be placed in the facility and observed for signs of FMD. A large area around the facility would be quarantined, where animal and human movement would be restricted or prohibited. In some cases, all susceptible animals within a two-mile radius would be also euthanized and disposed of properly by incineration or burial. In addition, APHIS has developed plans to pay affected producers the fair market value of their animals.
APHIS would consider vaccinating animals against FMD to enhance other eradication activities as well as to prevent spread to disease-free areas. However, vaccinated animals may still become infected and serve as a reservoir for the disease, even though they do not develop the disease symptoms themselves. Also for continued protective immunity, the vaccines must be given every few months.
APHIS is working with the U.S. Armed Forces to ensure that military vehicles and equipment are cleaned and disinfected before returning to the United States.
Preventing FMD from infecting and becoming established in an FMD-free area requires constant vigilance and a well-developed, thorough plan to control and eradicate any cases that might occur.
[Judith L. Sims ]
Haynes, N. Bruce, and Robert F. Kahrs. Keeping Livestock Healthy. North Adams, MA: Storey Communications, Inc., 2001.
Animal and Plant Health Inspection Service, U.S. Department of Agriculture. Foot-and-Mouth Disease. [cited June 2002]. <http://www.aphis.usda.gov/oa/fmd>.
Department for Environment, Food and Rural Affairs, United Kingdom." Origin of the UK Foot and Mouth Disease Epidemic in 2001. June 2002 [cited June 2002].
"History of the World's Worst Ever Foot and Mouth Epidemic: United Kingdom 2001." [cited June 2002]. <http://www.pighealth.com/fmdoutbreaks.htm>.