Diphtheria
Diphtheria is a serious infectious disease of the respiratory system caused by the bacterium Corynebacterium diphtheriae. Now a rare disease, it ravaged the world in the late nineteenth century and was a major killer of children. Symptoms included sore throat, fever, and body aches. The disease causes yellowish-gray mucous membranes to form and spread on the inner throat and nose. In some cases, the membrane can impede breathing, requiring a life-saving tracheotomy to open the windpipe. The infection can cause fatal damage if it spreads to the heart or kidneys. The disease is spread from person to person by coughing and sneezing and is more common among poor populations living in crowded conditions. The diphtheria bacterium produces toxins carried throughout the body by the bloodstream. These can be neutralized with injections of antitoxin. Antibiotics, such as erythromycin, are also used to treat the disease.
Diphtheria received its name in 1826 from French physician Pierre-Fidèle Bretonneau (1778-1862), who was the first to study its symptoms. He took the name from the Greek word for parchment to describe the membranes that form in the throat. Bretonneau was the first physician to perform a tracheotomy on a diphtheria patient, a four-year-old girl. He made an opening from her neck into her windpipe to enable her to breathe. The surgery was successful and saved the girl's life.
In the late 1800s, deadly diphtheria epidemics raged through Europe and the United States, and the scientific community rallied to find the cause and cure. Much of the research took place in the laboratories of microbiologists Louis Pasteur of France and Heinrich Koch of Germany. The rod-shaped bacterium responsible for diphtheria was first identified by two German bacteriologists working in Koch's laboratory--Edwin Klebs (1834-1913), who isolated the bacteria in 1883, and Friedrich August Löffler (1852-1915), who proved it was the causative organism by inducing diphtheria in laboratory animals with cultures of the bacteria.
Shortly after, French scientist Pierre-Paul-Emile Roux (1853-1933) and Swiss bacteriologist Alexandre Yersin (1863-1943), working at the Pasteur Institute in Paris, showed that a toxin produced by the bacillus was the actual cause of the disease. Roux, who was also known for his research on the anthrax and rabies viruses, made the first analysis of the toxin's chemical properties.
Once the cause of diphtheria had been identified, German bacteriologist Emil von Behring and Japanese scientist Shibasaburo Kitasato, who had been conducting research on the human body's ability to produce antitoxins to neutralize poisons produced by invading bacteria, were quickly able to develop a method to vaccinate individuals against diphtheria. They did this by injecting laboratory animals with sublethal doses of diphtheria toxin. Then they introduced blood serum of the animals containing antitoxin into humans to immunize them.
Behring and Kitasato's method was refined in the following decades. German microbiologist Paul Ehrlich developed standard dosages for their diphtheria antitoxin; and, in 1891, New York City pathologist Anna Wessels Williams isolated a stronger and more effective strain of diphtheria antitoxin. In 1894, Pierre Roux developed a diphtheria antitoxin serum using horses. He used this serum to successfully treat more than 300 cases of diphtheria. In 1913, Behring announced the development of a longer-lasting vaccine for diphtheria which was a mixture of toxin and antitoxin. The same year, Hungarian scientist and pediatrician Bela Schick (1877-1967) introduced a simple, reliable test to determine whether a person is susceptible to diphtheria. The Schick test involves injecting a small amount of toxin under the skin. If a red, swollen rash appears around the injection, the person is susceptible and should be immunized.
The incidence of diphtheria has declined dramatically since the large-scale introduction of diphtheria vaccine. The vaccine, which is injected into the forearm, contains diphtheria toxoid. This is a form of diphtheria toxin chemically treated to be nonpoisonous. The toxoid enables the body to build up antibodies to the disease so that, if the person becomes exposed to the germ, the disease will not develop.
One widely used vaccine for diphtheria is DPT, which also includes vaccines for whooping cough and tetanus. Three injections of this vaccine are recommended for children every few months after birth, followed by boosters at ages eighteen months, at four to six years, and then every ten years.
The research that led to the vaccine for diphtheria also created the scientific basis for the understanding of the body's immune system. Furthermore, research into the nature of diphtheria and other bacterial diseases at the turn of the century paved the way for the development of numerous antibiotics.
Despite the advances against diphtheria, diphtheria outbreaks still occur. These outbreaks can be large and spread rapidly. According to the National Coalition for Adult Immunization, one out of every 10 people who gets diphtheria will die from it.
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