What’s So Special About Foot-and-Mouth Disease?
Posted by nonbafks on August 11, 2008
Foot-and-Mouth Disease (FMD) is a severe, highly communicable disease of cattle, pigs, sheep, goats and deer. It is caused by one of the smallest disease producing viruses known. It has seven types and over 80 subtypes. Immunity to, or vaccination for, one type of the virus does not protect animals against infection from the other types. The strain now in England and Europe is harder on pigs and cattle but milder in sheep and goats. Humans do not catch the virus. The disease is characterized by blister-like lesions on the tongue, nose and lips, in the mouth, on the teats and between the toes which then burst, leaving painful ulcers. The blisters cause a heavy flow of sticky, foamy saliva that hangs from the mouth. Infected animals sway from one foot to the other due to the tenderness of the feet. Other symptoms include fever, reduced feed consumption, and miscarriages. Cattle and pigs, which are very sensitive to the virus, show disease symptoms after a short incubation period of 3 to 5 days. The incubation period in sheep is considerably longer, about 10 to 14 days, and the clinical signs of the disease are usually mild and may be masked by other diseases, thereby allowing FMD to go unnoticed.14 Although older cattle usually do not die from the infection, they suffer a severe illness which leaves them in a weakened state. They have high fevers, stop eating, give less milk, and become lame.
The virus is extremely contagious and spreads rapidly unless it is contained. This usually requires quarantining infected farms, followed by slaughtering and burning all susceptible animals. Anyone having contact with animals in infected countries should not go near susceptible animals for at least five days. Because the virus is spread so easily, countries with the disease are banned from exporting animals and their products, creating further economic hardship. Foot-and-Mouth Disease was last seen in the United States in 1929. The U.S. Government places an extremely high priority on keeping the disease out of the country. (http://cattletoday.info/foot_mouth.htm)
The FMD virus is easily transmitted and spreads rapidly. Before and during the appearance of clinical signs, infected animals release the virus into the environment through respiration, milk, semen, blood, saliva, and feces. The virus may become airborne and spread quickly if pigs become infected because pigs prolifically produce and excrete large amounts of the virus into the air. Animals, people, or materials that are exposed to the virus can also spread FMD by bringing it into contact with susceptible animals. For example, the virus can spread when susceptible animals come in contact with contaminated:
• animals and animal products, such as meat, milk, hides, skins, and manure;
• transport vehicles and equipment;
• clothes or shoes worn by people; and
• hay, feedstuffs, or veterinary biologics.15
FMD virus is the most infectious animal disease-causing virus. It has been determined that for certain strains, the dose required to infect cattle or sheep through inhalation is about 10 organisms. Infected pigs produce immense amounts of airborne virus. An infected pig exhales 400 million organisms per day. The sensitivity of cattle to infection and the high levels of airborne virus produced by infected pigs illustrate that the airborne spread of infection is another important factor in FMD outbreaks.
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