Foot-and-mouth disease

• 1. Introduction

  ›

  In 2001, foot-and-mouth disease, a viral illness of hoofed animals, forced Britain to postpone its general election by a month. The Isle of Man TT was cancelled, along with many other sporting events and leisure activities. A livestock disease had rearranged the national calendar. This documentary follows the virus behind that disruption. It asks how an illness that most animals survive can bring whole countries to a halt. It asks why governments sometimes kill healthy animals to stop it, and why a vaccine rarely settles the matter. It also asks how a few blisters on a cow's hoof can close borders and empty trade routes around the world.

  503864

• 2. Symptoms and Hosts

  ›

  The incubation period for foot-and-mouth disease runs from one to 12 days, and then a high fever arrives. In many animals it fades quickly, within two to three days. Blisters form inside the mouth and cause stringy or foamy saliva and heavy drooling. Blisters on the feet may rupture and leave the animal lame. Adults can lose weight and take several months to recover. Mature males may suffer swelling in the testicles, and a cow's milk production can fall sharply.

  Most infected animals eventually recover. The disease can still inflame the heart muscle and cause death, especially in newborn animals. The suffering is real even when the animal survives. The blisters are painful and make eating and moving difficult. Ruptured blisters also open the way for secondary bacterial infections.

  Cattle, water buffalo, sheep, goats, pigs, antelope, deer and bison are all susceptible. The virus has also infected hedgehogs and elephants. Llamas and alpacas may develop mild symptoms, but they resist the disease and do not pass it to their own kind. In laboratory experiments, mice, rats and chickens have been infected artificially. They are not believed to catch it under natural conditions.

  The last confirmed human case in the United Kingdom occurred in 1966. A few other cases have been recorded in continental Europe, Africa and South America, and some followed laboratory accidents. The virus is sensitive to stomach acid, so eating infected meat cannot infect a person, except in the mouth before swallowing. Human symptoms include malaise, fever, vomiting and red ulcerative lesions in the mouth, and sometimes small skin blisters. According to a newspaper report, the disease killed two children in England in 1884, supposedly through infected milk.

  A different illness, hand, foot and mouth disease, strikes young children far more often. It comes from certain non-polio enteroviruses and is distinct from the livestock disease, though both viruses sit within the family Picornaviridae. Because people so rarely catch the animal disease, it threatens agriculture far more than human health. Some have argued it is a zoonotic disease, one that crosses between species. The United States Centers for Disease Control and Prevention and the US Department of Agriculture do not count it as one.

  57363940

• 3. Hidden Carriers

  ›

  Some of the most dangerous animals on a farm are the ones that look perfectly well. Scientists describe two kinds of silent infection. A neoteric subclinical infection begins about one to two days after exposure and lasts roughly eight to 14 days. During that time the virus replicates heavily in the pharynx, the back of the throat, but does not enter the blood as it would in a clinical case. The animal appears healthy, yet it sheds substantial amounts of virus in nasal secretions and saliva. These infections often occur in vaccinated animals, though unvaccinated animals can have them too.

  The second kind is the carrier state. Cattle, buffalo, sheep and goats can keep a small amount of replicating virus in the pharynx for up to one to two years after an acute infection. Pigs cannot become carriers. Researchers do not fully understand why ruminants can and pigs cannot, or why some animals develop persistent infection while others do not.

  The risk from a single carrier is considered very low. Transmission from carriers has not been conclusively shown in field studies. In one experiment, though, virus collected from the pharynx of carrier cattle was placed in the pharynx of susceptible cattle. They developed the characteristic blisters in the mouth and on the feet. So transmission is unlikely, but not impossible.

  Regions where the disease is endemic hold many carriers, which may add up to more chances for spread. A healthy-looking animal that tests positive could be in either state, and the two carry very different risks. That uncertainty leaves veterinary officials guessing, and it shapes how countries think about vaccination.

  161920142

• 4. How It Travels

  ›

  In Canada in 1952, an outbreak flared up again after dogs carried off bones from dead animals. Wolves are thought to play a similar role in the former Soviet Union. Animals that never catch the disease can still move it from farm to farm. Daniel Rossouw Kannemeyer, who lived from 1843 to 1925, published a note in South Africa linking locusts covered in saliva to the spread of the disease.

  The virus also rides on objects. Motor vehicles, fodder, standing water and uncooked food scraps can harbor it, as can feed supplements made with infected animal products. The clothes and skin of farmers and other handlers carry it too. Cows can catch the disease from the semen of infected bulls. Over longer distances it can spread through the air.

  Species differ sharply in how they spread and receive the virus. Cattle are far more vulnerable than pigs to aerosolized virus. Infected pigs, however, produce 30 times as much aerosolized virus as infected cattle and sheep. Pigs are especially vulnerable through the mouth. Experiments have shown that pigs can be infected by eating commercial feed contaminated with the virus, which can stay active for long periods in some ingredients, especially soybean meal. Feed biosecurity became an important research area after a 2013 outbreak of Porcine Epidemic Diarrhea Virus in the United States, thought to have entered through contaminated feed.

  A famous claim holds that the virus once crossed 250 km over the English Channel through the air. Modelling studies do not support it, and most likely another route was responsible. Studies of cattle in the same stable suggest airborne spread between cattle is unlikely. Cattle can be infected easily by exposure to pigs that excrete the virus. Between cattle, spread depends mostly on virus deposited in the environment.

  Timing makes the disease harder to catch early. Animals can transmit it before any sign of illness. A 2011 experiment exposed susceptible cattle to serotype O virus in 24-hour increments and estimated an infectious period of 1.7 days. The cattle were infectious for only a few hours before fever or lesions appeared. Had detectable virus been used as a stand-in for infectiousness, the estimate would have been 4.2 to 8.2 days.

  A 2016 experiment with serotype A and pigs exposed in 8-hour periods found the pigs could spread disease for a full day before showing signs. Its analysis put their infectious period at roughly 7 days. Again, detecting the virus was not an accurate substitute for infectiousness. Those figures feed the epidemiological models that guide control policy.

  2833343529

• 5. A Shifting Virus

  ›

  In 1897, Friedrich Loeffler passed the blood of an infected animal through a Chamberland filter, a fine porcelain filter. The collected fluid could still make healthy animals sick, which showed that the cause was a virus. Later genetic work has traced how that virus changed. The virus has seven serotypes, labelled A, C, O, Asia 1, SAT 1, SAT 2 and SAT 3. An analysis of strains isolated between 1932 and 2007 put the mutation rate at about 1.46 × 10 minus 3 substitutions per site per year. That is similar to other RNA viruses.

  The same analysis placed the most recent common ancestor in the early 16th century. From there two clades arose, which gave rise to the Euro-Asiatic and South African strains alive today. By this estimate SAT 1 and SAT 2 split off roughly four centuries ago. The other serotypes diverged within the last century and a half. A reconstruction of past population size showed expansion in the early 20th century, then a rapid decline from the late 20th century to the present.

  This variety is a vaccine maker's nightmare. No cross-protection exists between serotypes, so a vaccine for one will not protect against any other. Even within one serotype, two strains may differ by as much as 30% in the sequence of a single gene. Vaccines must therefore match the strain involved, and the protection lasts only from months to years.

  Many early vaccines used dead samples of the virus, and they sometimes caused real outbreaks. In the 1970s, scientists found that a vaccine could be made from a single key protein of the virus. The remaining challenge was making enough of that protein. On the 18th of June 1981, the US government announced a vaccine against the disease, the world's first genetically engineered vaccine.

  The North American FMD Vaccine Bank sits at the Plum Island Animal Disease Center, 1.5 mi off the coast of Long Island, New York. It is the only place in the United States where scientists can work on highly contagious animal diseases of this kind. For that reason American companies usually do their foot-and-mouth work in countries where the disease is endemic. When an outbreak strikes, the virus must be analyzed before the correct vaccine can even be chosen.

  22734355

• 6. Fences and Culling

  ›

  Countries with no foot-and-mouth disease and no vaccination hold the strongest cards in the world meat trade. The World Organisation for Animal Health recognizes three states: disease present with or without vaccination, free with vaccination, and free without vaccination. Canada, the United States and the United Kingdom work hard to keep the third status. Brazil, Argentina, Botswana and Namibia, big beef exporters, vaccinate in some areas and keep other zones free of vaccination.

  Several reasons explain why vaccination costs a country export access. Routine blood tests based on antibodies cannot tell an infected animal from a vaccinated one, which hampers screening of export products. Widespread preventive vaccination could also hide the presence of the virus. And an animal infected shortly after vaccination can harbor and spread the disease without showing symptoms.

  Because vaccinated animals can become carriers, proving a country is free takes longer when vaccination is used instead of slaughter. Many disease-free countries therefore resist emergency vaccination out of concern for the trade and economic costs of a long wait. Under World Trade Organization rules, a country may export unprocessed animal products only to countries with an equivalent or worse status. The exceptions require risk mitigation steps such as vaccination, quarantine, and abattoir procedures like deboning, removal of lymph nodes and maturation of the meat.

  In Southern Africa, wild African buffalo carry the disease and have kept some states from gaining country-wide free status. Those states fenced off conservation areas and created free zones. Conservationists have criticized the veterinary fences for disrupting wildlife movement. Disinfecting materials at veterinary gates and during outbreak responses is another standard measure.

  The alternative is culling. Great Britain applied this stamping-out policy at the end of the nineteenth century, and it was later adopted across the whole European Union. It is among the most controversial measures, given its drastic nature and its psychological effect on farmers. In 2001, Britain's policy was to cull all animals within 3 km of an infected farm within 48 hours. That was described as "a response to a desperate situation, not a pre-meditated response to a known, assessed risk". The disease is usually not fatal to adult animals.

  For a farmer, culling can mean financial devastation, with contracts unmet and the farm, the equipment and future earnings at risk. Farmers in traditional systems may also feel emotional attachment to particular animals. Speed can shrink the toll. The 2007 outbreak was caught much earlier and was contained after culling only 1,578 animals.

  The broader bill is huge. Lost production and vaccination in endemic areas cost an estimated US$6.5 billion to 21 billion every year. Controlling outbreaks in normally free countries adds more than US$1.5 billion a year. Some of the poorest countries in the world bear that cost disproportionately.

  4547486451

• 7. Outbreaks Before 2000

  ›

  The northeastern coast of the United States saw the disease recognized in 1870, and the country has had nine outbreaks since. The most devastating came in 1914. It started in Michigan, then reached the stockyards of Chicago and became an epizootic, an animal epidemic. About 3,500 herds were infected, totaling over 170,000 cattle, sheep and swine. Eradication cost US$4.5 million. A 1924 outbreak in California led to the slaughter of 109,000 farm animals and 22,000 deer.

  Montebello, California, saw the most recent American outbreak, in 1929. Hogs had eaten infected meat scraps from a tourist steamship that had stocked meat in Argentina. Over 3,600 animals were slaughtered, and the disease was contained in less than a month.

  On the 26th of December 1946, the United States and Mexico jointly declared that the disease had been found in Mexico. Some Texans proposed an animal-proof wall along the border. The two countries cooperated instead and eradicated the disease without one. Radio broadcasts and speakers on trucks explained to Mexican ranchers why American veterinarians were treating their livestock. Ranchers whose cattle were culled received compensation. Tension still remained and led to clashes between local citizens and the military-protected veterinarians. The teams worked inward from outside the infected zone toward the heart of the epidemic, and by the end of 1950 they had given over 60,000,000 injections.

  In October 1967, a farmer in Shropshire reported a lame sow, later diagnosed with the disease. The suspected source was remains of legally imported infected lamb from Argentina and Chile. In all, 442,000 animals were slaughtered and the outbreak cost an estimated £370 million.

  On the 19th of March 1997, a sow at a farm in Hsinchu, Taiwan, was diagnosed with a strain that infects only swine. Taiwan had suffered epidemics in 1913-14 and 1924-29 and considered itself free of the disease as late as the 1990s. Mortality in the infected herd neared 100%. The cause was never determined, but the farm lay near a port city known for pig smuggling and illegal slaughterhouses.

  The disease spread at a rate of 200 to 300 new farms a day. Density was part of the reason, with up to 6,500 hogs per square mile, along with feeding pigs untreated garbage and farms close to slaughterhouses. A lack of laboratory facilities, slow response and the initial absence of a vaccination program all contributed. Swine vesicular disease, endemic in Taiwan, produces symptoms indistinguishable from foot-and-mouth disease, so earlier cases may have gone unnoticed.

  The military helped depopulate the swine. At peak capacity, 200,000 hogs a day were disposed of, mainly by electrocution. Burning and burial handled the carcasses, but burning was avoided in water resource-protection areas, and in April industrial incinerators ran around the clock. Vaccine began with 40,000 combined doses for zoo animals and valuable breeding hogs. Half a million more doses arrived at the end of March. On the 3rd of May, 13 million doses of the O-1 vaccine came. Only trained farmers, under veterinary supervision, could administer it, to limit the danger of vaccination crews spreading the virus.

  Taiwan had been the major pork exporter to Japan and one of the top 15 pork producers in the world in 1996. Over 3.8 million swine were destroyed at a cost of US$6.9 billion. The pig industry was devastated and the export market lay in ruins. Even in 2007, Taiwan was considered free of the disease but still ran a vaccination program, which restricts meat exports.

  5657556250

• 8. Outbreaks Since 2000

  ›

  The spring and summer of 2001 brought more than 2,000 cases on British farms, from the "Type O pan Asia" strain. More than six million sheep and cattle were killed before the epidemic ended in October. The county of Cumbria suffered most, with 843 cases. The crisis cost an estimated £8 billion across agriculture, support industries and the outdoor industry. What made it so serious was the delay between the first infection and the countermeasures, such as transport bans and detergent washing of vehicles and people entering livestock areas. Pigs fed insufficiently heat-treated rubbish probably started it, and the rubbish likely contained illegally imported infected meat.

  Ireland avoided disaster, with a single case in Proleek, County Louth. Strict controls on livestock sales, disinfection of everyone entering or leaving farms, and cancelled large events helped. Parliament later passed the Animal Health Act 2002 to give regulators more powers against the disease.

  In April 2005, an Asia-1 strain appeared in the eastern Chinese provinces of Shandong and Jiangsu. It spread to suburban Beijing, Hebei and Xinjiang. On the 13th of May, China reported the outbreak to the World Health Organization and the OIE, the first time it had publicly admitted to having the disease. Chinese media often use a euphemism, "Disease Number Five". In March 2010, the newspaper Southern Rural News ran an article titled "Breaking the Hoof and Mouth Disease Taboo". Provincial regulations on Disease No.5 exist from before the admission, such as Guangxi's 1991 regulation.

  Britain was hit again on the 3rd of August 2007, on farmland in Normandy, Surrey. All livestock nearby were culled the next day. A nationwide ban on moving cattle and pigs followed, with a 3-km protection zone and a 10-km surveillance zone. The strain was a "01 BFS67-like" virus, linked to vaccines and the 1967 outbreak. The likely source was the nearby Pirbright facility, 2.5 mi away, which made vaccines. On the 12th of September, a new outbreak was confirmed in Egham, 19 km from the first. Windsor Great Park, home to deer, stayed closed for three months.

  South Korea's most serious outbreak began in November 2010 on pig farms in Andong. In January 2011, officials began a mass cull of about three million pigs, roughly 12% of the national herd, and 107,000 of three million cattle. On the 10th of February 2011, North Korea reported an outbreak near Pyongyang, ongoing since at least December 2010. Illicit sales of infected meat hampered control efforts. In Japan, about 270,000 cattle were ordered slaughtered after infections in Miyazaki Prefecture.

  In May 2022, the disease returned to Indonesia, where it had been eradicated in 1986. Australian officials checked parcels and baggage from Indonesia and China and installed disinfectant floormats at airports. New Zealand, which has never had a case, banned meat products from Indonesian travellers.

  In January 2025, an outbreak in a herd of water buffalo near Berlin led to a 3 kilometre exclusion zone. On the 8th of March 2025, a cattle farm in Kisbajcs, Hungary, reported the first case there in 50 years, and all 1400 animals in the herd were destroyed. By the 21st of March the disease had crossed into Slovakia, and Slovak zoos closed temporarily. South Africa has also fought an outbreak since early 2025, with KwaZulu-Natal hit hardest. In early 2026, the US Department of Agriculture reported an outbreak in Russia.

  6572768088