Hoof and mouth disease, more commonly called foot-and-mouth disease (FMD), is an extremely contagious viral illness that affects cattle and other cloven-hoofed animals. It causes painful blisters in the mouth and around the hooves, leading to lameness, drooling, weight loss, and drops in milk production. While it rarely kills adult cattle, it devastates herds economically and triggers massive trade restrictions whenever it appears. FMD is not the same as hand, foot, and mouth disease in children, which is caused by a completely different virus.
What Causes It
FMD is caused by a virus in the family Picornaviridae, a group of small, hardy RNA viruses. Seven distinct serotypes exist: O, A, C, SAT1, SAT2, SAT3, and Asia. Within each serotype, many individual strains circulate. This matters because infection with one serotype does not protect against any of the others. Even within the same serotype, immunity from one strain may not fully cover a different strain. Serotype C has not been detected anywhere in the world since 2004, but the remaining six continue to circulate in various regions.
Signs and Symptoms in Cattle
The first signs typically appear 2 to 14 days after infection. A high fever lasting two to three days is usually the earliest indicator, often before any visible blisters form. Fluid-filled blisters then develop on the tongue, lips, gums, and inside the mouth, as well as around the hooves and on the udder. When these blisters rupture, they leave raw, eroded tissue surrounded by ragged fragments of loose skin.
Cattle with FMD produce sticky, foamy, stringy saliva that often hangs from the mouth. The mouth pain causes them to eat less, and hoof lesions make them reluctant to stand or walk. Dairy cows show noticeable drops in milk production. Pregnant animals can abort spontaneously, and some may become permanently infertile. In adult cattle, the mortality rate is generally low. Newborns and young calves are the exception: they can develop heart inflammation and die suddenly, sometimes before blisters even appear.
How the Virus Spreads
FMD spreads through virtually every route imaginable, which is what makes it so difficult to contain. Infected animals shed the virus in saliva, milk, semen, urine, feces, and the fluid from ruptured blisters. Direct contact between animals is the most straightforward transmission path, but the virus also travels through the air. Windborne spread can reach 20 kilometers under typical conditions, and in rare cases plumes of aerosolized virus have traveled up to 300 kilometers. Cattle are especially vulnerable to airborne infection because of the large volume of air they breathe.
The virus also hitches rides on boots, clothing, vehicles, and equipment. It can persist in organic matter for days to weeks under cool, moist conditions, and contaminated fodder or bedding can remain infectious for up to a month. Wool and hides can harbor the virus for anywhere from a few days to nearly a year depending on storage conditions. Refrigeration and freezing preserve the virus rather than destroying it. Inactivation requires either heat above 50°C (with a core temperature of 70°C for at least 30 minutes being the standard for animal products) or strongly acidic or alkaline conditions outside the pH range of 6.0 to 9.0.
Contaminated feed is another entry point. Feeding cattle unprocessed meat scraps, unpasteurized milk, or garbage containing infected animal products can introduce FMD to a herd that has never encountered it.
It’s Not the Same as Hand, Foot, and Mouth Disease
This is one of the most common points of confusion. Hand, foot, and mouth disease (HFMD) is a mild childhood illness caused by enteroviruses, most often coxsackievirus. According to the CDC, FMD and HFMD are caused by entirely different viruses. Humans cannot catch FMD from cattle, and cattle cannot catch HFMD from humans. The similar names are an unfortunate coincidence.
How It’s Diagnosed
FMD cannot be confirmed by looking at an animal. Several other diseases produce nearly identical blisters, including vesicular stomatitis and Seneca Valley virus infection. Any suspected case requires urgent laboratory testing. Veterinarians collect tissue from unruptured or freshly ruptured blisters, or failing that, blood or throat swab samples.
In the lab, the virus can be grown in cell cultures to confirm its presence. The most common rapid test is an ELISA, which detects viral proteins and identifies the specific serotype involved. Real-time RT-PCR, which amplifies fragments of the virus’s genetic material, matches the sensitivity of cell culture and allows labs to process large numbers of samples quickly. Blood tests for antibodies are used to certify that individual animals are free of infection before international trade or to check whether vaccinated animals have developed adequate immunity.
Where FMD Still Occurs
Most of North America, Western Europe, Australia, New Zealand, and Japan have been free of FMD for decades. The disease remains endemic across large parts of Africa, the Middle East, and South and Southeast Asia. Several South American countries have achieved freedom through extensive vaccination programs, though some maintain designated free zones rather than nationwide status. Paraguay and Uruguay, for example, are recognized as free while still practicing vaccination.
Countries that have earned FMD-free status without vaccination remain under constant threat. Even a single introduction can trigger catastrophic consequences. The 2001 outbreak in the United Kingdom led to the slaughter of over 6 million animals. Global production losses and vaccination costs in regions where FMD is endemic are estimated at $6.5 to $21 billion per year, with outbreaks in previously free countries adding over $1.5 billion annually on top of that.
Vaccination Challenges
Vaccines against FMD exist and are widely used in endemic regions, but they come with significant limitations. Because vaccination against one serotype provides no cross-protection against the other six, and even strains within the same serotype can differ enough to reduce vaccine effectiveness, it’s more accurate to think of FMD vaccination as needing 20 to 25 different vaccines rather than one. A single dose in cattle provides about six months of protection when the vaccine is well matched to the circulating strain. Boosters are required to maintain immunity.
Countries that are currently free of FMD generally avoid routine vaccination. Vaccinated animals produce antibodies that are indistinguishable from those of infected animals in standard tests, complicating surveillance. Newer, highly purified vaccines allow labs to differentiate vaccinated from infected animals through specialized testing, but this adds cost and complexity.
What Happens During an Outbreak
When FMD is confirmed in a free country, the response is fast and aggressive. The standard approach, known as “stamping out,” involves killing all clinically sick animals and any susceptible animals that had contact with them. Strict quarantine zones are established, and movement of livestock, vehicles, and people is tightly controlled. Thorough cleaning and disinfection of all contaminated premises, equipment, and vehicles follows.
Depending on the scale of the outbreak, authorities may also deploy emergency vaccination in a ring around infected premises to slow spread. Vaccinated animals may later be slaughtered, sent to commercial processing, or in some scenarios allowed to live out their productive lives. The specific strategy depends on how widespread the outbreak is, how quickly it can be contained, and the logistical capacity to depopulate and dispose of animals. Personnel responding to outbreaks must wait 24 to 72 hours before moving between infected and uninfected farms to avoid carrying the virus on their bodies or clothing.
For cattle producers, the practical reality of an FMD outbreak means potential loss of their entire herd, prolonged quarantine periods, and an immediate halt to any sales or movement of animals. Even producers whose herds are never infected face market disruptions, as importing countries typically ban all livestock and meat products from any nation with an active outbreak.