History of Foot-and-Mouth Disease
Outbreaks in North America

ARS 91-58-1 -- May 1969
Agricultural Research Service / U.S. Department of Agriculture

Foot-and-Mouth Disease

A Menace to North American Livestock

Click here for map showing prior North American FMD outbreaks.


Foot-and-mouth disease outbreaks have occurred within the borders of the United States and its North American neighbors -- Mexico and Canada -- in past years.

Now free of the disease, the three countries are in a continuing state of alert against entry of this devastating vesicular malady affecting cloven-footed animals.

The three North American countries have a similar approach to combating the disease: (1) Prevent entry by rigidly restricting the importation of cattle and other susceptible livestock and potentially contaminated byproducts or materials from countries where foot-and-mouth diseases exist; (2) prevent spread of the disease should an outbreak occur; and (3) eradicate the disease as speedily as possible if it does appear.

Reasons behind the determination to keep out foot-and-mouth disease include:

North America knows from experience the high cost of outbreaks and the drastic measures required to wipe out the disease. However, experience of countries where the disease has become endemic shows that the costs of "living with" the disease are likely to be much greater. If the disease becomes entrenched, direct and indirect economic losses may run as high as 25 percent of the total value of the livestock industry of the Nation.

Prevention--A Mutual Concern

Because of contiguous borders, the countries of North America have a common concern in keeping out foot-and-mouth disease (FMD). Their mutual welfare requires that prompt and effective action be taken to control and eradicate the disease should it gain entry. For this reason, The United States cooperated with Mexico in fighting foot-and-mouth disease after it broke out there in 1946. Similarly, when Canada confirmed its 1951 outbreak in early 1952, the Canadian Government invited observers from the United States to study its eradication program.

The last outbreak of the disease in the United States ended in 1929. Foot-and-mouth disease has not been reported in Mexico since 1954. Canada has been free of the disease since 1952 when their last outbreak was quickly stamped out.

The Disease and How It Strikes

Foot-and-mouth disease is one of the most dreaded of all animal diseases. Primarily a disease of cattle and swine, it also infects other cloven-footed animals including sheep, goats, deer, antelope, and buffalo. Although foot-and-mouth disease does not rank with some other foreign diseases as a killer, its highly contagious nature and the heavy economic losses resulting from outbreaks make it a major threat.

The disease is caused by one of the smallest viruses known. Seven different types of the virus are known and within each type many subtypes have been identified. These seven major types of foot-and-mouth disease virus are: type A, type O, type C, type SAT-1, type SAT-2, type SAT-3, and type Asia-1. With one exception, the type A virus was responsible for the outbreaks of foot-and-mouth diseases that have occurred since 1929 in North America. A single outbreak in a single herd with type O virus occurred in Mexico.

Under favorable circumstances, the virus may remain infectious for long periods in animal carcasses, byproducts, straw, and bedding, and even pastures. It can be readily spread by contaminated animals, persons, vehicles, and materials that bring the virus in contact with susceptible animals.

Temporary immunity to one or more types of the virus due to vaccination or recovery from an acute infection will not protect against other types of the virus. Immunity is of short duration -- usually lasting only a few months.

Disease symptoms include fever, and blisters in the mouth, between the toes, and on the teats. The first signs of infection usually are excessive salivation due to the mouth lesions and severe lameness due to foot sores. These signs are indistinguishable from hose of other diseases characterized by vesicles or blisters. Consequently, prompt reporting and laboratory diagnosis are essential when animals show symptoms of vesicular disease.

The mortality rate from the disease is generally low in mature animals, but death losses in very young,m old, and very fat animals may be high. Newborn calves from sick cows often die because of a lack of sufficient milk production from the mother cow. When the disease strikes mature animals, major losses result from reduced productivity, abortions, loss of condition, and inability of draft animals to work because of lameness. The last was particularly important during outbreak in Mexico where oxen were used as draft animals.

Disease Widely Scattered Throughout the World

Foot-and-mouth disease is widespread in Europe, Asia, Africa, and South America. This makes it difficult for individual nations on those continents to achieve and maintain freedom from foot-and- mouth disease and necessitates continual vigilance on the part of the North American countries to keep the disease from gaining a foothold on this continent.

Besides the countries of North and Central America, livestock-producing countries that were free of foot-and-mouth disease at the time this report was written (May 1969) include Australia, the Channel Islands, the Fiji Islands, Greenland, Iceland, Japan, New Zealand, Northern Ireland, Norway, and the Republic of Ireland.

United States Outbreaks and Their Cost

In all, the United States has suffered from nine outbreaks of foot-and-mouth disease. Three of these occurred before the turn of the century -- in 1870, 1880, and 1884. Since 1900, six outbreaks have occurred -- in 1902, 1908, 1914, 1924 (two separate outbreaks), and 1929. All the outbreaks occurring before the turn of the century were traced to importation of infected livestock; but, since the development of a Federal system of inspection and quarantine of imported livestock, no outbreak has been attributed to admission of live animals.

The 1870 outbreak spread into New England and New York but was arrested within a few months.

About 1880 the disease was found in three lots of imported animals, but the disease was confined to the animals originally affected.

The 1884 outbreak occurred in Portland, Maine, but died out without spreading.

The 1902 outbreak spread into Massachusetts, Vermont, New Hampshire and Rhode Island,infecting 244 herds involving more than 5,000 animals before the disease was eradicated in 1903. this outbreak was originally believed to have been introduced through infected hay, fodder, or other materials from ships sailing from foreign ports. However, later evidence pointed to cowpox virus, imported from Japan for manufacturing smallpox vaccine for humans, as the source of the infection.

An outbreak in 1908 spread from Detroit through the State of Michigan and into New York, Pennsylvania, and Maryland. Before the last quarantine was lifted in April 1909, 157 herds involving 2,023 cattle, 275 sheep, 1,329 swine, and 7 goats had to be destroyed. The infection was traced to the same lot of contaminated cowpox virus that was responsible for the 1902 outbreak.

The largest outbreak in the United States occurred in 1914. The disease, first diagnosed in October, spread rapidly after it gained entry into the Chicago stockyards and other stockyards in the East. Before the outbreak ended in September 1915, the disease had infected more than 3,500 herds in the District of Columbia and 22 States -- Connecticut, Delaware, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Massachusetts, Michigan, Minnesota, Montana, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Virginia, Washington, West Virginia, and Wisconsin. More than 3,500 herds, including about 77,000 cattle, 85,000 swine, 10,000 sheep, 100 goats, and 9 deer had to be sacrificed in eradicating the disease.

The exact origin of the 1914 outbreak is unknown. One theory is that the infection may have been introduced with tanning industry materials brought to Niles, Michigan, from abroad.

In 1924, two unrelated outbreaks occurred -- one in California and the other in Texas. In all, more than 900 herds of cattle, swine, sheet, and goats, totaling over 100,000 animals, were condemned in the California outbreak. More than 22,000 deer were destroyed. Over 109 percent of them showed lesions of FMD. The Texas outbreak infected 148 herds involving 8,473 cattle, 27 sheep, and 69 swine before the last quarantine was lifted on January 1, 1925. About 7 months later foot-and-mouth disease recurred in Texas from July 30 to October 14, 1925. The infection was found on the same ranch and pasture as the first case found in 1924. As a precaution against another outbreak, the quarantine was kept in force until April 1, 1926. Altogether, 1,001 herds were infected and 20,850 cattle, 752 swine, 1,402 sheep, and 345 goats were destroyed.

The source of the 1924 outbreak in California was traced to raw garbage removed from ships returning from foreign countries.

Although the origin of the Texas outbreak in 1924 was not conclusively determined, it was thought to have been brought in by foreign ships docking at the port of Galveston. Sailors from foreign ships were known to frequently bathe and wash their clothes in a water tank in the pasture where the first 1924 outbreak was discovered.

The 1929 outbreak occurred in California on January 19. Quarantines were established and the infection was contained within the State. In all, 277 infected or exposed cattle, 3,291 swine, and 23 goats were destroyed. The California outbreak was traced to garbage from ships returning from foot-and-mouth disease infected countries.

Cost figures on foot-and-mouth disease outbreaks occurring before 1900 are not available.

Direct costs and indirect losses to the Nation from the six outbreaks that occurred between 1902 and 1929 are estimated at $253 million. The direct cost for indemnifying owners of condemned livestock and administrative costs to the Federal and State governments of the eradication campaigns were about $23 million. Indirect losses were conservatively estimated to be 10 times the direct cots -- or about $230 million. These losses resulted from reduced production of meat and dairy products, the adverse effect on allied industries, and loss of export markets due to embargoes.

Spurred by these heavy losses, Congress in 1930 passed a law strengthening the Nation's defenses against the entry of foot-and-mouth disease. It prohibits importation of susceptible animals and fresh-chilled or frozen meat from countries where foot-and-mouth disease exists. Entry of potentially contaminated products is also very strictly regulated under the law. This legislation was embodied in the Tariff Act of 1930 with strong backing from the livestock industry and veterinary-regulatory officials of the Federal and State governments. Since the enactment of this legislation, no outbreaks of foot-and-mouth disease have occurred in this country.

Also, in 1930, the United States and Mexico entered into a treaty agreeing not to import ruminants or swine from countries in which foot-and-mouth disease or rinderpest exists.

The Fight Against Foot-and-Mouth Disease in Mexico

The first organized campaign against foot-and-mouth disease in Mexico was started in February 1926 to control an outbreak in the vicinity of Frontera in the State of Tabasco. Although the outbreak was first reported in the fall of 1925, the disease was not positively identified until the following February after a team of Mexican and American veterinarians investigated the outbreak.

The Frontera area was then relatively isolated from the big cattle trade and travel centers of Mexico. This was favorable to success of the eradication campaign that was launched by the Mexican Government. Even so, the outbreak had spread from Tabasco into parts of the adjoining States of Campeche, Chiapas, and Yucatan before the disease was eradicated in November 1926. In all, 465 cattle, 730 sheep, and 3 swine were slaughtered during the eradication campaign. Source of the 1925-26 outbreak is not known, although evidence points to cattle brought to the State of Tabasco in a banana boat.

The most persistent and costly outbreak of foot-and-mouth disease suffered by a North American country was that which started in Mexico in late 1946 in the State of Veracruz. The disease appeared not long after the importation of Zebu cattle from Brazil.

Unfortunately, the disease was not immediately recognized, because it was mistaken at first for "yerba," or grass disease, as vesicular stomatitis was then called in Mexico. In December 1946, the infection was identified as foot-and-mouth disease. The diagnosis was confirmed by tests conducted at the foot-and-mouth research laboratory in Pirbright, England, and the virus was found to be type A. To prevent entry of the disease into the United States, importation of all cloven-footed animals was temporarily halted at the international border until it was officially closes on January 3, 1947, in accordance with the 1930 Tariff Act.

The delay in diagnosis had given the disease time to spread from the original point of infection over a wide area of Mexico through the free movement of exposed animals. Early in 1947, for example, the disease was spreading at the rate of about 500 square miles a day.

On April 2, 1947, the Mexico-United States Commission To Eradicate Foot-and-Mouth Disease was formed. Headed by a Mexican citizen, the Commission included high government officials, veterinarians, and administrative personnel of both countries. In addition, an advisory committee representing the U.S. livestock industry was named.

Both countries agreed to the goal of eradication. This called for inspection of all cattle in areas where the disease might have spread, quarantine to prevent further spread of the disease, slaughter of all animals found to be infected or exposed, safe disposal of carcasses by deep burial, and disinfection of contaminated premises.

Considerable time was required to assemble the trained personnel and equipment needed for conducting such a large-scale campaign.

Before the control and eradication measures could be put into effect, the infection had spread through an area of nearly 260,000 square miles extending in an irregular band across central Mexico from the Gulf of Mexico to the Pacific.

U.S. and Mexican personnel worked together in conducting the eradication campaign. The United States contribution to the campaign included services of animal-disease-control specialists, vehicles and equipment, administrative personnel, and million of dollars to help defray the costs of paying indemnities to owners of animals slaughtered to eradicate the disease.

Mexican troops enforced the quarantines to prevent the disease from being spread further through the movement of infected livestock.

Many problems had to be overcome in waging a successful eradication campaign over a vast area, which included thinly settled mountain regions and tropical forests. Even locating and rounding up livestock for inspection was difficult in such terrain. In some cases, new roads or landing strips had to be built in order to get heavy equipment to inaccessible outposts. For example, earth-moving equipment was needed for quickly digging trenches to bury carcasses of exposed and infected animals. Also, the task of patrolling a farflung and fluctuating quarantine line in a largely fenceless area was difficult.

Although vital to stop the spread of foot-and-mouth disease, slaughter of infected and exposed animals worked a hardship on farmers who depended on the animals for their livelihood. Condemned animals were appraised, and the owners were paid indemnities. Nevertheless, families who had cow or goats for their milk, pigs for meat, and oxen for plowing suffered food loss until replacement animals could be provided.

By working together, Mexican and U.S. disease workers made progress toward controlling the outbreak by the late months of 1947. However, it had been necessary to kill large numbers of livestock and, by November of that year, nearly 900,000 animals had been slaughtered including cattle, swine, sheep, and goats.

To relieve the stress on the Mexican national economy from such large-scale slaughter of animals, a vaccination plan was added to the original program and slaughter was tapered off. This plan, known as the Aleman-Ortiz Garza plan, was put into effect in June 1948.

The modified program was aimed at limiting spread of the disease by vaccinating all animals within the quarantine zone. This area, which stretched in a wide band across central Mexico from the Gulf of Mexico to the Pacific Ocean, contained approximately 17 million susceptible animals.

Large quantities of vaccine were needed to put the new program into effect. Consequently, more than a million does of vaccine were purchased from Europe and South America in February 1948. Cases due to the vaccine occurred from time to time and there was evidence in some cases that the vaccine was ineffective. Plans were drawn for building a plant for producing vaccine in Mexico. By July 1948, the plant was completed and in operation.

Under the new plan, vaccination teams worked in successive waves inward from the periphery of the quarantine zone. This line of attack was designed to limit and reduce the infected area by building up an immune population. To maintain resistance against the infection, the plan called for revaccination of susceptible animals every 4 months. When infection was found within the quarantine zone, the program of regularly scheduled vaccination was supplemented by slaughter of animals known to be infected and exposed. In addition, "ring" vaccination -- that is, vaccination of animals in all hers around a seat of infection -- was followed. The plan also called for disinfecting premises that were possibly exposed, then testing with healthy animals to see if any infection remained.

In October 1949, type O foot-and-mouth disease appeared in a Mexican herd within the quarantine zone. This could have had grave consequences to the eradication campaign since the vaccination program protected only against type A infection. Fortunately, early detection of the type O virus made it possible to contain and eliminate the disease through prompt and effective quarantine and eradication measures.

By August 1950, 60 million does of vaccine had been administered and the vaccination program was terminated. In 9 of the 10 districts in the quarantine area, all susceptible animals had been vaccinated at least four times. A fifth round of vaccinations was initiated in at least one of the nine districts. In the tenth district, vaccination was discontinued after three series had been completed. During the vaccination program 10,362 infected and exposed animals were destroyed.

After termination of vaccination, the program went into a phase of inspection and vigilance which was to continue for a year. As a result of this vigilance, a December 1950 outbreak in the Municipio of Espinal, Veracruz, was quickly detected and eradicated. This outbreak required the slaughter of 62 cattle and 389 other animals. A second outbreak, occurring in August 1951 in another section of Veracruz, was eradicated after 1,430 cattle and 430 other animals were slaughtered.

In September 1952, after 12 months without any known infection, Mexico was judged to be free of foot-and-mouth disease, the U.S. embargo against cattle from Mexico was lifted, and the campaign was formally concluded. However, a total of 1,001,465 animals had to be slaughtered to eradicate the disease and the direct cost to the United States of the 1947-52 campaign was about $127 million.

Fortunately cooperative efforts of the neighboring countries to hold foot-and-mouth disease in check did not stop with opening the border. After the Mexico-United States Commission to Eradicate Foot-and-Mouth Disease had completed its task, the Mexico-United States Commission for the Prevention of Foot-and-Mouth Disease was formed to maintain vigilance.

Wisdom of maintaining constant vigilance was demonstrated 9 months later when a new outbreak was found in La Isla, Municipio of Gutierrez Zamora, Veracruz, in May 1953. The source of the infection is not know, but it was of the same type that plagued Mexico during 1946-52. Evidently a carrier animal that was exposed during the previous outbreak was responsible for the new outbreak. Again, under provisions of the Tariff Act of 1930, it became necessary to close the border between the United States and Mexico. This new outbreak was quickly controlled and eradication was completed in April 1954--less than a year after it was first reported. Following a period of waiting and testing, Mexico was again declared free of foot-and-mouth disease in December 1954 and the second campaign formally ended. This new campaign required the slaughter of more than 23,000 animals and cost the United States $6 million, including costs for border patrol. It was, however, dramatically less costly than the 1946 outbreak, which struck before the United States and Mexico had built up a joint system of defense against the disease.

The two campaigns to rid Mexico of foot-and-mouth disease were long and costly. It took more than 7 years--from April 1947 to April 1954 to clean out the last vestiges of the two outbreaks. At the height of the eradication drive some 8,000 men were fighting the disease -- Mexican and U.S. citizens working together.

Total costs to the United States of the two campaigns added up to around $136 million. This overall total includes short-term research as well as salaries of campaign personnel, funds to indemnify owners of condemned livestock, and expenditure for canned meat purchased by the United States in Mexico for overseas distribution.

Cash expenditures by the Mexican Government included salaries of civilian and military personnel working in the campaign and a contribution to indemnity payments. In addition to the loss of milk and meat, the livestock industry was disrupted. Stockmen outside the quarantine area suffered, important export markets were lost, and cattle price dropped. Consequently, the cattle population in northern Mexico built up to a high density. To alleviate this situation and provide an outlet for Mexican livestock products, the United States helped develop a meat- canning factory in Mexico that would meet U.S. food import requirements. After inspection showed that the meat was processed under conditions that made it safe, our Government purchased considerable quantities for distribution by the United Nations Relief and Rehabilitation Administration.

Campaign Accomplishments

Eradication of foot-and-mouth disease from Mexico in the two campaigns marked a milestone in control of animal diseases. For the first time, two sovereign nations successfully cooperated in eradicating a serious disease of livestock that had become widespread and entrenched.

Successful conclusion of the campaigns meant that foot-and-mouth disease had not gained a permanent foothold in North America. Although 7 long years, much hard work, and great sacrifices by farm families and campaign personnel, as well as millions of dollars, went into the effort, it was worth the price. If the infection had been permitted to spread northward to the international border, keeping it out of the rest of North America would have been impossible and the costs would have been incalculable.

To Mexico, eradication meant that the productivity and value of their livestock would not be permanently reduced by this debilitating disease. It also meant that foreign markets would be reopened to the sale of Mexican livestock and fresh and frozen meat.

Canadian Outbreak Controlled Quickly

After many years without foot-and-mouth disease, Canada in February 1952 confirmed the presence of a type A FMD virus in cattle herds near Regina in the Province of Saskatchewan. Veterinarians of the U.S. Department of Agriculture had been alerted by the Canadian Government at the first suspicion of an outbreak and at its invitation participated in the diagnosis.

Upon confirmation of the presence of foot-and-mouth disease in Canada, animal disease control officials of the two neighboring countries launched an emergency campaign to keep the infection from spreading throughout Canada and into the United States.

Exposed and infected animals were slaughtered on 24 premises found to be infected. Carcasses were buried as soon as possible, under difficult weather conditions, in pits dug 5 1/2 feet deep in frozen ground.

In April 1952, the original quarantine area was extended following discovery of foot-and-mouth disease near Weyburn -- within 50 miles of the North Dakota and Montana borders.

Immediately following confirmation of the foot-and-mouth disease outbreak in Saskatchewan, the United States suspended imports of cattle, goats, swine, and other susceptible animals and their fresh and frozen meats from Canada. This was in accordance with Federal quarantine regulations, which prohibit the importation of susceptible animals or their fresh or frozen meats, hides, and other products from countries where foot-and-mouth disease exists. However, nearly 6,000 susceptible animals (mostly cattle) had been imported from Canada during the early weeks of 1952 after foot-and-mouth disease appeared in Saskatchewan but before it had been diagnosed. All these imports were traced to their destination and kept under observation until the incubation stage in the development of foot-and-mouth disease had passed. Luckily, none of the animal from Canada developed foot-and-mouth disease.

At the same time, the United States inspection force and border patrol was strengthened, and disease control officials and practicing veterinarians and livestock producers throughout the country were alerted to watch for and report suspicious symptoms. This alert was continued until Canada had wiped out the last traces of foot-and-mouth disease.

Canada was declared free of foot-and-mouth disease on March 1, 1953, following a long period in which no cases had been found. The last infection was reported in April 1952.

With the aid of strong eradication and control measures, Canada was able to hold he 1952 outbreak within a relatively small area of Saskatchewan and to quickly eliminate the disease. Similarly, the Untied States was successful in preventing foot- and-mouth disease from again entering the country.

Continuing Need for Guarding Against Foot-and-Mouth Disease

The North American continent has remained free of foot-and-mouth disease outbreaks for more than a decade. However, this does not justify relaxing safeguards against entry of the disease. In fact, a number of developments make ceaseless vigilance against this dread foreign disease more important than even.

The movement of SAT-1 type foot-and-mouth disease out of Africa into southern Europe has been a grim reminder that this disease may be caused by any one of the seven known virus types striking from different lands.This virus spread rapidly through the Near East after it was first reported on the Island of Bahrain in the Persian Gulf in January 1962 -- and within weeks was found in Iraq, Israel, Syria, Lebanon, Libya, and Jordan. By June 1962, confirmed cases were reported from Turkey.

Outbreaks involving A, O, and C types of FMD virus occur frequently throughout most of Western Europe, but no outbreaks involving type SAT-1 have been reported there. A severe outbreak involving type A22 (Near East Strain) FMD virus was reported in Russia in the late summer of 1965. This marked the first known appearance of this strain in Europe and has caused great concern because European livestock have not been exposed to the strain and could be highly susceptible. Furthermore, vaccines used for controlling other strains of type A virus are ineffective against A22 (Near East Strain). These vaccine therefore would be of no value to European countries that use the "live-with" vaccination approach to controlling foot-and- mouth disease if an outbreak involving this strain occurs.

Severe outbreaks of foot-and-mouth disease, caused by classic strains of A, O, and C types of FMD viruses, occurred during 1965 and 1966 in a number of other European countries, including Spain, Portugal, West Germany, Switzerland, and Holland.

In the winter of 1967 and early 1968, England and Wales were undergoing the most serious foot-and-mouth disease outbreak of their recorded history. By the end May 1968, about 430000 head of livestock had been slaughtered in bringing the disease under control. A group of veterinarians for the U.S. Department of Agriculture went to England to help in the campaign and to gain technical experience in the British methods of eradicating foot-and-mouth disease.

Animal health authorities of Great Britain, like those of the United States, are convinced that eradication, though costly, is the cheapest and most effective way of dealing with foot-and- mouth disease. The heavy toll of foot-and-mouth disease in Europe -- where the "live-with" approach is the policy of most countries -- provides strong evidence in support of adhering to an eradication policy wherever it is economically possible.

Chances of rapid international spread of disease are also increased by the growing volume of livestock shipments and the continuing worldwide speedup in transportation. This has had the effect of shrinking global distances and diminishing the effectiveness of water barriers protecting the continent from entry of foreign diseases.

Within the United States, a similar increase in the mobility of livestock and acceleration in transportation have taken place. Consignments of livestock move much faster now than in 1929, when our most recent outbreak of foot-and-mouth disease occurred. For example, cattle leaving Chicago arrive in New York 16 hours later. These rapid animal movements often outrun the incubation period of the disease, which could be spread widely before infected animals show obvious symptoms.

Under the U.S. marketing system, livestock from many sources are assembled at marketing centers and shipped in mixed lots from one end of the country the other for milking, feeding, breeding, or slaughter. Consequently, the risk of rapid spread of foot-and-mouth disease would be great if infected animals were not detected before they got into trade channels.

USDA's quarantine inspectors at pots of entry guard against the introduction of foot-and-mouth disease and other diseases and parasites affecting animals. Federal regulations prohibit the interstate movement of animals affected by communicable diseases. Federal inspectors keep a close watch on animals moving interstate commerce through public stockyards and other centers of livestock travel and trade. The States are responsible for controlling and eradicating animal diseases within their borders, and they cooperate with USDA's animal health programs affecting all the States. Active cooperation on the part of practicing veterinarians and individual farmers is crucial to the success of animal disease-control programs. In guarding against foot-and-mouth disease, it is especially important to report animals showing symptoms of vesicular disease for laboratory diagnosis. Because of the similarity of symptoms, it is not possible to distinguish between foot-and-mouth disease, vesicular stomatitis, and vesicular exanthema by visual examination.

Research continues to give strong support to regulatory services by developing improved methods for diagnosing the various types of foot-and-mouth disease and other animal diseases and for preventing their spread.

In 1954, before foot-and-mouth disease was finally eliminated from Mexico, the U.S. Department of Agriculture started construction of a foreign diseases research laboratory particularly concerned with foot-and-mouth disease. To eliminate any danger of the virus escaping and entering the United States mainland, an island site, off Long Island, N.Y., was selected and a maximum security system provided in building and operating the research facility.

Research is now underway at this facility -- the Plum Island Animal Disease Research Laboratory. Laboratory researchers found that the foot-and-mouth disease virus is capable of tolerating curing processes previously thought adequate to destroy the virus. This knowledge has led to a modification in regulations regarding the admission of cured meats from countries where foot-and-mouth disease exists. The laboratory has also been successful in purifying, concentrating, and electronically photographing foot-and-mouth disease virus.

Mexico and Canada are also maintaining their guard against foot- and-mouth disease. The three countries of North America are cooperating in their common fight to keep out the disease.

The Mexico-United States Commission for the Prevention of Foot-and-Mouth Disease still maintains a small group in Mexico -- ready to put eradication measures into immediate effect should the need arise. In addition to a small staff of Mexican employees, two U.S. veterinarians are on duty. Also, vigilance committees of Mexican stockmen and veterinarians are pledged to maintain a volunteer watch for sick animals with symptoms similar to foot-and-mouth disease and to report any suspicious cases promptly to the Commission.

In July 1968, the defenses of North America against the invasion of foot-and-mouth disease was further strengthened. The United States and five Central American countries and Panama launched anew cooperative program for developing better mutual protection against foot-and-mouth disease and rinderpest. Under authority recently granted by Congress, the U.S. Department of Agriculture is authorized to provide experienced personnel to help Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, and Panama establish effective programs to prevent, detect, or eradicate foot-and-mouth disease and other foreign animal diseases.

The fact that this continent has remained free from foot-and-mouth disease for more than a decade is not just a happy accident of geography or evidence that the disease has been vanquished. Rather, it shows that the systematic guard maintained by the nations of North America has been successful to date -- and should be maintained in face of the continuing threat of foot-and-mouth disease from abroad.

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