Diphtheria

Definition:

An acute infectious disease caused by the toxin-producing bacteria Corynebacterium diphtheriae. It usually affects the respiratory tract (primarily the larynx, tonsils, and throat). But it can also affect the skin, and the toxin produced by this bacteria can damage the nerves and heart.

Causes, incidence, and risk factors:

Diphtheria is found only in humans and is usually transmitted by respiratory droplets from infected persons or asymptomatic carriers, but can be transmitted by contaminated objects or foods (such as contaminated milk). The incubation period is 2 to 5 days.

The bacteria primarily infect the nose and throat although they may initially infect the skin producing skin lesions. C. diphtheriae produces a toxin which causes tissue damage (necrosis) in the immediate area of the infection, usually the nose and throat. It can spread via the bloodstream to other organs where it can cause significant damage. Although the toxin can damage any tissue, that of heart and nerves are most frequently and most severely affected.

The localized infection in the throat and tonsillar area produces a characteristic membrane which is gray to black in color, tough, and fibrous. It  can cause airway obstruction.

If toxin enters the bloodstream the patient may develop  into myocarditis which is the most worrisome complication. Toxic effects on the nervous system may cause temporary paralysis.

The disease is now rare because of widespread immunization.

Risk factors are crowding, poor hygiene, and lack of immunization.

In 1993 and 1994 the separated states of the former USSR experienced a diphtheria epidemic with over 150,000 reported cases and 5,000 deaths. The epidemic was related to a drop in routine childhood immunizations (DPT) to less than 60% compliance, failure to give booster doses to adults, and worsening economic conditions in the affected countries.

Symptoms:

• Sore throat ranges from mild to severe with painful swallowing, hoarseness. Drooling suggests that airway obstruction is about to occur.
• Fever and chills.
• Bloody, watery (serosanguineous) drainage from nose.
• Croup-like (barking) cough.
• Stridor.
• Apnea may occur with apnea.
• Skin lesions can be seen in cutaneous diphtheria (usually seen in the tropics).

Lab Tests:

• Culture and Gram stain of membrane or throat culture to identify Corynebacterium diphtheriae.
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• In individuals with myocarditis, the electrocardiogram (ECG) is often abnormal.

Treatment:

Diphtheria antitoxin is given as an intramuscular or intravenous injection as soon as the diagnosis is suspected.

Antibiotics such as penicillin or erythromycin.

People with diphtheria require hospitalization for supportive treatment and during the administration of antitoxin. Insertion of an endotracheal tube and/or removal of the obstructing membrane may be required if airway obstruction is present. Intravenous fluids, oxygen, bed rest and cardiac monitoring (due to the possibility of myocarditis) are usually indicated.

Immunization or booster of all contacts of the infected person, including health care personnel, is indicated. Individuals found to be carriers of diphtheria are treated with antibiotics as well.

Vaccination
DTaP (diphtheria and tetanus toxoids and acellular pertussis vaccine) is the vaccine of choice.

Schedule:

• Under age of 7 years: DTaP at 2mo-4mo-6mo-15or18 mo.
• After age of 7 years: Td at  0-4weeks-6mo. Booster every 10 days.

Protective immunity is not present longer than 10 years after the last vaccination,

Individuals recovering from the natural disease should be vaccinated.

Adverse Reactions following vaccination:

• Local redness, pain occasional skin abscess.
• Arthus type hypersensitivity reaction may occur in persons having received multiple boosters.

Contraindications to vaccinations:

• Allergic reactions to previous vaccines.
• Severe acute disease.

Storage:

2 to 8 degree C

Prognosis

The death rate is 10%. Recovery from the illness is slow; therefore, activities must be resumed slowly.

Complications:

• The diphtheria toxin can damage the heart, nervous system, kidneys, or other organs resulting in disorders such as:
• Myocarditis which can lead to heart failure.
• Neurologic palsies or peripheral neuritis causing uncoordinated movements and other symptoms (develops in 3 to 7 weeks). Severe nerve damage can cause paralysis.
• Kidney damage or nephritis may also occur.

Prevention:

• Routine childhood immunizations (DPT) and adult booster (DT) prevent the disease.
• Outbreak control with vaccination-antibiotic therapy of victims and contacts.

Dr. Paul Assad

REF:

Epidemiology and prevention of vaccine preventable diseases. CDC 6^th Ed. Jan 2000