What Is Hoof and Mouth Disease in Cattle?

Hoof and mouth disease, more formally called foot-and-mouth disease (FMD), is one of the most contagious viral diseases of livestock. It is caused by an RNA virus that targets cloven-hoofed animals and produces painful blisters on the mouth, tongue, feet, and teats of cattle. The disease spreads with alarming speed, can devastate an entire herd within days, and triggers immediate trade restrictions that ripple far beyond the affected farm. Though adult cattle usually survive, the economic fallout from an outbreak is so severe that many countries treat even a single confirmed case as a national emergency.

The Virus Behind the Disease

FMD is caused by an RNA virus belonging to the genus Aphthovirus. It comes in seven distinct serotypes that circulate unevenly across Asia, Africa, and South America, with several subtypes within each serotype.¹ This matters practically because infection with one serotype does not protect against the others, and vaccines have to be matched to the circulating strain. A vaccine built around serotype O, for instance, will not shield a herd from serotype A. The virus itself is remarkably hardy in the right conditions, surviving for weeks in cool, damp environments and on contaminated equipment.

How FMD Spreads

Direct contact between infected and healthy animals is the primary route of transmission.² An infected cow sheds enormous quantities of virus in saliva, nasal discharge, milk, and from ruptured blisters on the feet. But indirect routes are what make FMD so hard to contain. The virus can travel through the air, sometimes over considerable distances under the right weather conditions. It can also hitch rides on boots, clothing, tires, and shared feeding equipment. Livestock trucks that move between farms without proper cleaning are a classic conduit. Even raw milk transported by tanker can carry virus from an infected farm to a processing facility, spreading it along the route.³

The role of different species adds another layer of complexity. In mixed-species herds, cattle tend to be both more infectious and more susceptible than sheep. Research comparing transmission from sheep to cattle found that sheep shed less virus and play a more limited role in spreading the disease than cattle do in mixed populations.⁴ That said, sheep can carry the virus with fewer visible symptoms, which means they sometimes spread it quietly before anyone raises an alarm.

What Infected Cattle Look Like

The hallmark of FMD in cattle is the formation of fluid-filled blisters, or vesicles, on the tongue, gums, dental pad, lips, teats, and the coronary band of the hooves (the junction where the horn of the hoof meets the skin). These blisters rupture within a day or two, leaving raw, painful erosions. Infected cows drool heavily, smack their lips, and are reluctant to eat. Lameness is often the first thing a farmer notices, because blisters on the feet make walking agonizing.⁵

Under the microscope, the damage is extensive. The outer layers of skin and mouth lining show swelling and degeneration of cells, with inflammatory cells flooding into the tissue. Blisters form within the deeper layers of the skin, and severe cases progress to full-thickness erosions with dead tissue at the base.⁶ While morbidity in a herd can approach 100 percent, mortality in adult cattle is usually very low. The real production losses come from weight loss, a dramatic drop in milk yield, and secondary bacterial infections that set in through the open sores.

Why Calves Are at Serious Risk

Young calves face a completely different prognosis. While adults recover, mortality in calves can reach 50 percent, primarily because the virus attacks the heart muscle.⁵ Research on calves under two months old has shown that those developing signs of heart involvement had dramatically elevated blood markers of cardiac damage compared to healthy calves or older infected calves. Necropsy of calves that died revealed a characteristic gross lesion known as “tigroid heart,” where pale streaks of dead heart muscle alternate with darker normal tissue, creating a striped pattern visible to the naked eye.⁷ This cardiac form of the disease is age-dependent, hitting the youngest calves hardest and tapering off as they grow older. It is why FMD outbreaks on dairy farms with young stock can turn catastrophic quickly.

Carrier Cattle and Persistent Infection

One of the most frustrating aspects of FMD is the carrier state. After recovering from the acute illness, a portion of cattle continue to harbor live virus in the back of the throat for months, sometimes over a year. The virus persists specifically in the epithelial cells of the soft palate and pharynx.⁸ Even vaccinated cattle that were never visibly sick can become carriers if they are exposed to the virus. In vaccinated animals, the virus stays restricted to the pharynx throughout both early and persistent phases of infection, never spreading to other tissues the way it does in unvaccinated animals.⁹

Whether carrier cattle actually transmit the virus to other animals under field conditions is a subject that has generated decades of debate. The theoretical risk is clear, but documented cases of a carrier animal sparking a new outbreak are rare. Regardless, the existence of carriers complicates eradication enormously. Countries trying to prove they are FMD-free after an outbreak must demonstrate that no carriers remain, which is one reason trade restrictions can persist long after the last visible case has resolved.

Diagnosing FMD

Clinical diagnosis is tricky because FMD looks nearly identical to several other vesicular diseases. Vesicular stomatitis and swine vesicular disease produce such similar blisters and erosions that lab testing is the only way to confirm which virus is responsible.¹⁰ This is why any suspicion of FMD triggers urgent sample collection and laboratory investigation, even in countries that have been free of the disease for years.

Traditional testing relies on sandwich ELISA, which detects viral proteins in tissue samples. But molecular methods have proven more sensitive. A comparison of diagnostic approaches found that real-time PCR, multiplex PCR, and a technique called RT-LAMP all detected virus in 100 percent of tissue samples, while sandwich ELISA caught only about 86 percent.¹¹ These molecular methods also identify the specific serotype simultaneously, which is critical for choosing the right vaccine and understanding which strain is circulating. Virus has also been successfully detected in milk samples using RT-PCR, which has implications for dairy surveillance during an outbreak.¹²

Vaccination and the DIVA Problem

Vaccination is one of the main tools for controlling FMD in countries where the disease is endemic. But it creates a tricky surveillance problem: how do you tell a vaccinated animal from one that has actually been infected and recovered? Both will test positive for antibodies against the virus’s outer coat proteins. The solution lies in testing for antibodies against nonstructural proteins, which are produced inside infected cells but are not present in properly purified inactivated vaccines. An animal that has been infected will develop antibodies to these internal proteins; a properly vaccinated-only animal will not.

Several DIVA (Differentiating Infected from Vaccinated Animals) tests have been developed around this principle. One approach using a panel of recombinant nonstructural proteins showed that all experimentally infected cattle developed antibodies to at least four nonstructural proteins, while vaccinated animals that had received fewer than five doses typically produced antibodies to only one and were negative for the key marker, a protein called 3ABC.¹³ A newer ELISA based on a synthetic peptide from the 3B protein achieved a sensitivity of about 97 percent for detecting infected animals, with specificity above 99 percent for both naive and vaccinated cattle.¹⁴ These tests are essential for countries that vaccinate but still want to trade internationally, because importers need assurance that an animal is truly disease-free and not just symptom-free because of vaccination.

Outbreak Response Strategies

When FMD appears in a previously free country, the response is swift and severe. The standard approach, sometimes called “stamping out,” involves killing all infected and exposed animals, imposing strict movement controls, and intensively disinfecting affected premises. The 2001 outbreak in the United Kingdom became a case study in how difficult this can be at scale, with millions of animals culled and the government subsequently identifying lessons around contingency planning, carcass disposal, emergency vaccination readiness, and animal traceability.¹⁵

Modeling studies have since explored when and how vaccination should supplement culling. Multiple models consistently show that ring vaccination beginning within about a week of detection outperforms delayed vaccination, and that a 3-kilometer vaccination radius tends to be the sweet spot, offering meaningful protection without the logistical burden of vaccinating every farm for 5 kilometers around.¹⁶ Cross-country comparisons have reinforced that early vaccination with sufficient vaccine supply consistently outperforms other strategies, and that vaccinating only cattle-holding farms can produce results comparable to vaccinating all species.¹⁷

In places where FMD is near-endemic and resources are limited, the calculus shifts. Research on vaccine rationing suggests that when supply is tight, the best long-term approach combines rapid ring vaccination during active outbreaks with carefully paced prophylactic vaccination throughout the year, spreading the available doses to maintain coverage as long as possible rather than using them all up at once.¹⁸

Disinfection on the Farm

Because the virus can survive on surfaces, boots, and equipment, biosecurity depends heavily on choosing the right disinfectant. Not all products work equally well. Testing of commercially available disinfectants found that acidic ethanol-based products, alkaline cleaners, and sodium hypochlorite (bleach) all achieved strong reductions in viral load. In contrast, neutral ethanol disinfectants, ordinary hand soaps, and quaternary ammonium sanitizers had little effect.¹⁹ Electrolyzed water has also shown promise, with highly acidic or alkaline formulations cutting viral loads by more than 99.99 percent within two minutes. The mechanism differs by type: acidic formulations rely on chlorine content, while alkaline versions appear to physically degrade the viral RNA itself.²⁰

The practical takeaway for farmers and veterinarians is that pH matters. The FMD virus is vulnerable at extremes of acidity and alkalinity but relatively stable in the neutral range. Standard hand soap and generic alcohol sanitizers are not reliable for decontamination during an outbreak.

The African Buffalo Problem

In southern Africa, control of FMD faces an obstacle that no amount of farm-level biosecurity can fully solve. The African buffalo is a natural reservoir of the virus, carrying it indefinitely without showing illness.²¹ Where buffalo ranges overlap with cattle-grazing areas, spillover events drive most outbreaks. Field studies have confirmed that the rate of FMD infection in nearby cattle populations correlates with how frequently the two species come into contact.²² Vaccination of cattle in these border zones helps reduce individual-level risk but has not been enough to stop the virus from moving out of the wildlife reservoir and into domestic herds.

This wildlife interface is one reason why complete global eradication of FMD remains elusive. You can stamp out the virus in domestic animals, but if it circulates silently in wild buffalo populations, reintroduction is always a dry-season fence failure away. The dynamics have been quantified as a key example of how persistent pathogens maintain themselves through wildlife reservoirs.²³

Raw Milk as a Transmission Route

An infected cow begins shedding virus into her milk before clinical signs appear, and she continues shedding throughout the acute phase of disease. This means raw milk collected during the incubation period can carry virus without anyone knowing the herd is infected. Milk tankers picking up from multiple farms along a route can spread contamination across a wide area before the first blister is noticed. One concern raised by researchers is that current minimum pasteurization standards may not completely eliminate FMD virus in all situations.³ Raw milk and raw milk products fed to calves or pigs on other farms have historically been implicated in spreading outbreaks, and restrictions on animal product imports from affected countries are a routine consequence of any confirmed case.²⁴

Economic Fallout

The financial damage from FMD goes far beyond dead or culled animals. Direct losses include reduced milk production, weight loss in meat animals, reproductive failures, and the cost of treating secondary infections. Indirect losses pile on through vaccination programs, trade restrictions, and the inability to adopt improved production practices in regions where the disease is always lurking. One estimate placed the combined annual cost of visible production losses and vaccination in endemic regions at between $6.5 and $21 billion, with outbreaks in previously free countries adding another $1.5 billion or more per year.²⁵

Trade impacts deserve special emphasis. When a country loses its FMD-free status, export markets close overnight. Rebuilding that status takes years of surveillance and proof that no virus is circulating. For export-dependent livestock industries, a single confirmed case can cause billions in lost revenue before a single animal dies.

Not the Same as Hand, Foot, and Mouth Disease

A persistent source of confusion is the similarity in names between foot-and-mouth disease of livestock and hand, foot, and mouth disease in children. They are entirely unrelated. Hand, foot, and mouth disease is caused by enteroviruses, most commonly coxsackievirus A16, and is a routine childhood illness in humans. FMD very rarely affects people; isolated human cases have been documented through close contact with infected animals, but the virus does not spread efficiently in human populations and poses no meaningful public health threat.²⁶ When news of an FMD outbreak in cattle makes headlines, the rush of worried parents calling pediatricians is a predictable consequence of the confusing naming.

The Toll on Farmers

Something that rarely makes it into the veterinary literature but is devastatingly real is the psychological impact of an FMD outbreak on the people who raise the animals. During the 2001 outbreak in the Netherlands, a survey of over 660 dairy farmers found that roughly half of those whose animals were culled experienced severe post-traumatic stress symptoms.²⁷ These were not people who lost a business asset; they lost animals they had bred, raised, and cared for daily, often for generations. Research in India similarly found that livestock owners perceived FMD as causing permanent asset loss and that the experience heightened psychological stress across the family.²⁸ The mental health dimension is increasingly recognized as part of the full cost of the disease, distinct from the economic numbers and just as consequential for rural communities trying to rebuild after an outbreak.