FOOT-AND-MOUTH DISEASE

(FMD) also called foof-and-mouth disease, or aftosa a highly contagious viral disease affecting practically all cloven-footed mammals, including cattle, sheep, goats, and swine. Wild herbivores such as bison, deer, antelope, reindeer, llama, camel, giraffe, and elephant are also susceptible. The horse is resistant to the infection. The disease is characterized by the formation of painful fluid-filled vesicles (blisters) on the tongue, lips, and other tissues of the mouth and on parts of the body where the skin is thin, as on the udder and teats, between the two toes of the feet, and around the coronary band above the hoof. There are seven major immunologically distinct types of the foot-and-mouth virus, and these types affect different species and produce symptoms of differing severity. The virus is spread by both inhalation and ingestion, and it has an affinity for epithelium (the covering of the skin and mucous membranes of the gastrointestinal tract); it forms a primary vesicle where it gains entrance in the body. Within 24 to 48 hours it enters the bloodstream, causing fever. During this phase, lasting 24 to 36 hours, the virus is excreted in the saliva, the milk, the urine, and the feces. A characteristic smacking of the lips then usually becomes prominent in the infected animal, ushering in the phase of the formation of vesicles on the tongue, gums, and lips of the mouth. These vesicles rupture in about 24 hours, leaving raw, inflamed, and extremely painful surfaces that heal in one to two weeks. By this time the animal refuses to eat solid food. Blisters also appear on the foot, causing lameness. The losses caused by foot-and mouth disease are tremendous. The mortality in ordinary mild epizootics (animal epidemics) is only about 5 percent, but malignant forms of the disease have led to losses of up to 50 percent. In those animals that survive, great losses in weight occur because the animals cannot eat. In surviving milk-producing animals the flow of milk is sharply diminished. Abortions and mastitis are common, and secondary infections are frequent. Foot-and-mouth disease is endemic throughout much of Europe, Asia, Africa, and South America. The virus can survive for relatively long periods of time in the air, in food and garbage, and even in hides, hair, and wool, so measures for controlling the disease are necessarily rigorous. A diagnosis of the affected animals must be made quickly and the area quarantined, after which all infected or susceptible animals are slaughtered and their carcasses burned. Other contaminated objects are cleaned and disinfected, and the farm or other quarantined area is left uninhabited for several months. The development of effective vaccines has helped control epidemics but has not eliminated the disease. As a result of strict quarantine measures and the prompt destruction of infected animals, North America has remained largely free of the disease; the last major outbreak in the United States was in 1929. There is no effective treatment for infected animals.