Diphtheria Symptoms and Treatment
Diphtheria is an acute contagious infection that chiefly affects children. For many years it was one of the most serious contagious diseases, occurring in epidemic form throughout the world. In recent decades the disease has become much less prevalent in western Europe and North America, but in many other parts of the world it is still a serious problem.
Cause and Symptoms of Diphtheria
Diphtheria is caused by the bacterium Corynebacterium diphtheriae. Although diphtheria bacteria may enter the body through the skin, genitals, eyes, or ears, the most common site of infection is the upper respiratory tract. Usually, the bacteria become lodged in the nose, throat, and windpipe, from which they can be easily transmitted to other people in droplets of respiratory secretions. Sometimes a person may harbor the bacteria without developing any recognizable symptoms, and he may spread the disease without knowing it.
After the bacteria become established in the respiratory tract, they begin multiplying and producing a poisonous substance known as diphtheria exotoxin. The exotoxin is then carried by the bloodstream to other parts of the body, where it produces characteristic symptoms. The onset of symptoms occurs suddenly, usually after an incubation period ranging from 1 to 4 days. Among these symptoms are moderate fever (usually less than 102°F, or 38°C), chills, general malaise, and a mild sore throat accompanied by a brassy cough. At this time, the mucous membrane lining the upper respiratory tract becomes coated with a layer made largely of dead cells and bacteria.
In response to the presence of diphtheria exotoxin, the body produces a neutralizing substance known as diphtheria antitoxin. If the antitoxin is produced promptly enough and in large enough amounts, it enables the patient to recover from the disease. The antitoxin also provides an immunity to the disease for at least several months and usually longer.
Although an uncomplicated recovery from diphtheria is the general rule, the exotoxin sometimes impairs the functioning of the heart and peripheral nerves. These complications usually arise 2 to 4 weeks after the onset of the disease. Involvement of the heart may produce myocarditis, or inflammation of the heart muscle. If the nerves are affected, a temporary paralysis may result.
Treatment of Diphtheria
The only effective treatment of diphtheria is the prompt administration of antitoxin to neutralize any exotoxin still circulating in the bloodstream. The first effective diphtheria antitoxin was produced by the German scientist Emil von Behring in 1890. Although the commercial preparation of antitoxin today is slightly different from von Behring's method, the basic principle is the same.
In preparing diphtheria antitoxin, small amounts of diphtheria exotoxin are injected into horses. After several injections, diphtheria antitoxin appears in the horses' blood. The blood serum, which contains the antitoxin, is then separated from the other blood components ana is processed under sterile conditions before it is administered to diphtheria patients. Because horse serum is a foreign protein in the human body, its administration is sometimes followed by severe sensitivity reactions (anaphylactic shock), and it is important that the antitoxin be injected only after the patient has been given special tests to determine his sensitivity to the serum.
In addition to administering antitoxin, the physician also treats any serious symptoms that develop during the course of the disease. If the layer coating the throat membrane becomes so thick that it completely obstructs the air passageway, the doctor performs a tracheotomy, making an incision in the throat and inserting a tube into the windpipe. Following the patient's recovery, the tube is removed and the incision is closed. In some cases the windpipe is not completely obstructed, and the doctor may enable the patient to breathe more easily by inserting a thin silver tube into the windpipe, a procedure known as intubation. In most cases, however, it is not necessary to resort to either tracheotomy or intubation.
The administration of antibiotics, such as penicillin and streptomycin, has not proved to be of any value in treating diphtheria. General supportive measures, such as bed rest and increasing the patient's intake of fluids, are helpful in making the patient comfortable.
Prevention of Diphtheria
The only method of preventing diphtheria is to immunize susceptible people. The substance used in immunizing an individual is diphtheria toxoid, which is made by treating diphtheria exotoxin with formalin, a chemical that destroys the poisonous qualities of the exotoxin without impairing its ability to stimulate the body's formation of antitoxin. The immunity that results from administering diphtheria toxoid lasts for at least several months and usually longer. It is common practice to administer the toxoid to children before the age of 1. A booster dose is usually given 2 or 3 years later, and again when the child enters school.
Because a person may have had diphtheria without knowing it, the only way to determine if he has had the disease is to test his immunity to it. The most widely used test for determining a person's state of immunity to diphtheria is the Schick test, which was first developed in 1913 by the Hungarian-American pediatrician Bela Schick. In this test, a small amount of diphtheria exotoxin is introduced into the skin. If the area becomes reddish over a period of 3 or 4 days, the person is susceptible to diphtheria. If no reaction occurs, the level of antitoxin in the person's blood is high enough to protect against the disease.