June 21, 2003
MEXICAN-US FMD CAMPAIGN 1947-1954
In the United States, foreign animal diseases were once a scourge of livestock and initially led to the development of the veterinary profession itself (Corrie Brown, Threat of Accidental Foreign Animal Disease Introduction, AVMA Annual Meeting, July 23, 2000).
In the context of recent initiatives by the European Union to move emergency vaccination to the forefront of control measures instead of being a last resort, Dr. Jerry Callis* was kind enough to share that the consternation that confronted the Dutch and British during their recent FMD problems, to vaccinate or not, was also experienced by the United States and Mexicans during the 7 year fight against FMD from 1947-1954:
"Initially, USDA was determined to eradicate by slaughter. For several years the Mexicans went along with this idea, but after slaughtering 1 million animals, the campesinos rebelled, stating-you have killed 1 million animals, we still have FMD, can we not do something else like vaccinate? With great reluctance USDA agreed. Suitable vaccine could not be purchased. Vaccine was indeed purchased from at least 4 laboratories in Europe and South America, and determined not suitable, thus the decision to begin from scratch and make the vaccine in Mexico. Having no buildings, no protocol, etc., this was a serious undertaking. However, over 18 months, 76 million doses were produced, every lot was quality controlled and then applied, resulting in eradication, following which, no vaccine was stockpiled, and the buildings used for production of the vaccine were destroyed."
In an interesting note concerning
the U.S. flu epidemic in 1918. The guy who wrote the booklet (Studies
of Foot-and-Mouth Disease Vaccine, and Related Observations in Mexico 1946-1954)
M.S.Shahan was in charge of the US Mexican campaign to eradicate FMD and
served as the first director of Plum Island. He was a young officer
in the military in 1918, stationed in Kansas and almost died from the flu.
At one point he was indeed pronounced dead but a colleague came to his
rescue, treatment continued and he recovered to live a full life. Frank
Mulhern was involved in the campaign from day one until the finish. He
later was head of what is now APHIS for many years- retired from that Agency
then joined the group responsible for eradicating ASF from DR and Haiti.
He also championed eradication of hog cholera from the US while in APHIS.
Interestingly- hog cholera- classical swine fever in Europe, is still present
in Europe and causes big problems at times. Their wild boars are infected
and are the source of some infections.
SUMMARY: STUDIES OF FOOT-AND-MOUTH DISEASE VACCINE, AND RELATED OBSERVATIONS IN MEXICO 1946-1954 - Mexico-United States Commission for Prevention of Foot-and-Mouth Disease, Mexico, D.F., Mexico
Foot-and-mouth disease (FMD was officially diagnosed in Mexico in December, 1946. The prevalent causative virus was identified early in 1947 as Type A FMD virus.
Organization of the Mexico-U.S. Commission for Eradication of Foot-and-Mouth Disease was formalized April 2, 1947. The Commission was reconstituted in September, 1952, under the designation: Mexico-U.S. Commission for Prevention of Foot-and-Mouth Disease. However, the new agreement was not formally effective until the last recognized signature was affixed in November 1952.
Through systematized inspections, quarantines, slaughter of more than one million infected and exposed animals, disinfection, and the application of more than 60 million doses of Type A vaccine in cattle, goats, sheep and swine, FMD was eradicated from Mexico. The campaign against the disease began in early 1947 and ended in late 1954. During this period, vaccine was used from 1948 to August, 1950, while the other procedures continued as necessary to the end of the program.
A total of 383 lots of Type A vaccine, each consisting of 9,000 to 200,000 doses (intradermal), were produced and tested. In controlled tests, only one lot of the vaccine protected as few as 63 percent of the vaccinated test cattle against generalization. Only 8.9 percent of the vaccines protected less than 80 percent of the vaccinated animals, and 40 percent of the vaccines protected 95 percent or more. In these tests the over-all average protection from all the vaccines produced in Mexico was 89.3 percent.
The materials and methods used in producing and testing the vaccine are described.
Essentially equal protection of cattle against generalization of the virus resulted from either intradermal or subcutaneous vaccination.
Although 2 ml. doses of vaccine were effective in test cattle in preventing generalization, the resistance of treated animals decreased substantially within 3-4 months after vaccination. Larger doses were effective for a slightly longer time. Doses smaller than 2 ml afforded some protection against generalization for short periods of time.
Cattle in poor condition and underweight at the time of vaccination were protected to a lesser extent when exposed 2 weeks after vaccination than animals in comparatively good condition. At later times of exposure, however, when the condition of all cattle was comparable, protection was essentially equal.
FMD virus of the type and strain used in Mexico, stored for as long as 12 months, was shown to be still antigenically effective when compounded into vaccine.
Vaccines stored for periods of time up to 20 months gradually decreased in potency, but would still have been acceptable for use in case of need in emergencies, which never arose.
Although swine were less protected in a controlled test than cattle, swine were continually vaccinated in the field with 1 ml doses, as were goats and sheep.
There were more deaths after exposure in experimental control cattle than in vaccinated cattle, and the localized and generalized lesions in controls were generally more extensive and severe than in the vaccinates. Thus, even partially protected vaccinates could be expected to lessen the over-all impact of the disease in serious situations where vaccine is used for control.
Type A FMD virus persisted in Mexico until the last known outbreak was eliminated in April, 1954. Type O virus was identified in an outbreak on 1 premises in October. 1949. Although this virus was exceptionally virulent, it never spread from these premises where the affected and exposed animals were promptly slaughtered and buried. The exact source of the type O virus was never determined.
Complications due to vesicular stomatitis (VS) are discussed. Although sheep were found to be artificially susceptible to some Mexican strains of the virus, natural infections in sheep were not discovered.
The rational for use of FMD
vaccine and for discontinuance of vaccination are discussed.
* Jerry Callis: DVM (AUB
'47), MS (PUR '49). D SC (Honorary, PUR '79, Honorary, Southhamptom College
of Long Island University '80). ACVM-1967. General. (Charter Diplomate).
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