A Look at Diphtheria – Its Causes, Symptoms and Treatment

Diphtheria is an acute, highly contagious, toxin-mediated infection that's preventable by vaccine. Diphtheria is rare in the UK but remains a serious problem in some other parts of the world. There have only been eight cases since 1986, and all of those have returned from abroad.

What causes it
Diphtheria is caused by an infection of Corynebacterium diphtheriae, a grampositive rod that usually infects the respiratory tract (primarily the tonsils, nasopharynx and larynx). It's more serious when it occurs in infants because they have smaller airways, which are more susceptible to obstruction because of their size.

How it happens
The infection is transmitted by:

• contact with an infected patient's or carrier's nasal, pharyngeal, eye or skin lesion discharge
• contact with articles contaminated with the bacteria
• ingestion of unpasteurised milk.

Incubation and communicability
The diphtheria incubation period is 2 to 7 days. The period of communicability is 2 to 4 weeks after the onset of symptoms, or until 4 days after the initiation of antibiotic therapy.

What to look for
Symptoms of diphtheria include:

• fever
• malaise
• purulent rhinitis
• cough, hoarseness and stridor
• cervical lymphadenopathy
• pharyngitis.

Obstruction production
The infection, localised to the tonsils and posterior pharynx, is characterised by a thick, patchy, greyish green, membranous lesion that can lead to airway obstruction. Some children also exhibit infectious, ulcerated skin lesions as a manifestation of the disease.

What tests tell you

• Culture specimens from the nose, throat and skin lesions reveal the presence of coryneform organisms.
• Sensitivity tests determine the optimal antibiotic therapy.
• Serologic testing will identify the presence of diphtheria toxin.

Complications
Infection with the toxin can result in myocarditis, thrombocytopoenia, peripheral neuropathy or an ascending paralysis with symptoms similar to Guillain-Barré syndrome. Renal, cardiac and peripheral CNS damage may also occur.

It's a cover-up
The membranous lesion that covers the tonsils can spread to cover the posterior pharynx, which can result in airway obstruction. Removal of the membrane may be indicated, but attempting to do so can cause bleeding. Left untreated, however, it can result in death.

How it's treated
Diphtheria is treated with antitoxin and antibiotics.

No time to waste
IV administration of diphtheria antitoxin and antibiotic therapy must begin within 3 days of the onset of symptoms. The patient should be tested for allergy to horse serum before administering the antitoxin. The antibiotic of choice is usually penicillin G or erythromycin for those allergic to penicillin.

Too close for comfort
Close contacts of the infected child should be identifi ed, monitored for signs of illness and treated with prophylactic antibiotic therapy (oral erythromycin for 7 to 10 days). Cultures of the nose, the throat and skin lesions should be obtained.

What to do
Diphtheria is a preventable disease. The immunisation series is designed to begin at age of 2 months. The vaccine confers immunity for 10 years, after which boosters should be given every 10 years throughout the lifespan. Passive immunity conferred from the presence of maternal antibodies lasts as long as 6 months after birth.

Diagnose, then act
When the disease is diagnosed, follow these steps:

• Report the infection to the local public health department.
• Place the infected child in droplet isolation to prevent respiratory transmission. (Show the child isolation gowns, masks and gloves that will be worn and provide a simple explanation such as, 'your parents, nurses and doctors are going to wear these so everyone stays healthy'.)
• Institute contact isolation precautions if skin lesions are present.
• Maintain infection precautions until after two consecutive negative nasopharyngeal cultures to prevent spread of the disease.
• Closely monitor the child for signs of airway obstruction. Provide humidified oxygen, if oxygen is ordered, to reduce airway inflammation.
• Administer antitoxin and antibiotics as ordered. Monitor for allergic or anaphylactic reaction.
• Maintain the child on complete bed rest to prevent myocarditis. Provide age-appropriate activities to prevent boredom.

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