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Hippocrates first described it in the 4th century BC. During the 17th century European epidemic, the Spanish called it “El garatillo” [the strangler]. By 1735 it had spread to New England, swiftly killing entire families. By 1900, it was one of the leading causes of death for infants and children.

Diphtheria has left its mark on the world's populations. Prevalent in areas of poverty and places where people live closely together, it is one of the fastest moving and most contagious diseases. Its usually young victims, if not attended to immediately, die quickly, either from the suffocating effect of the toxin-produced thick grayish membrane that coats the throat and blocks airways or from the spread of toxin into the blood-stream, which causes heart failure and, at times, paralysis.

Several scientists and physicians were instrumental in finding a cure for diphtheria. Edwin Klebs, in 1883, identified the bacterium that causes it. In 1884, Friedrich Loeffler cultivated the bacterium, identifying it as Corynebacterium diphtheriae. But the turning point in controlling the disease came in 1891 from two bacteriologists, Emil Adolph von Bohring from Germany and Shibasaburo Kitasato from Japan. Following on the work of Pierre Roux, von Behring and Kitasato demonstrated that when an animal (they first used guinea pigs, then goats, and finally horses) is injected with the diphtheria toxin, the animal's immune system will respond by producing antibodies or antitoxins (a word coined by von Behring). This “antidiphtheric serum” can then be removed from the animal, purified, and injected into the human patient. The serum neutralizes the disease-causing toxins, bringing relief to the afflicted.

Horses were already valued as a major source of transportation and now, because of their large size, also became the best source for producing large quantities of this antitoxin. The need for easily accessible, healthy horses became great. Edward Shorter, in the The Cambridge Illustrated History of Medicine, describes a London doctor receiving the antitoxin from “certain horses kept near Harrow for the purpose.”

Although some patients had allergic reactions to the horse antibodies, the antitoxin was extremely effective in saving lives. In 1927, Alexander Glenny developed a vaccine against diphtheria, and mass immunization in the United States after World War II greatly reduced the incidence of the disease. By 1970, it had also been eliminated in most developing countries.

Diphtheria has not disappeared, however. Between 1990 and 1998, the former Soviet Union suffered a devastating epidemic resulting in over 5,000 deaths. Even in the United States, isolated cases have been reported in Native American communities from the Northern Plains areas. And today, over 100 years since von Behring's discovery, the diphtheria antitoxin is still used, and horses are still being used to produce it.

© 2000 Association of American Medical Colleges