Pertussis - Causes, Symptoms and Treatments

Also known as whooping cough, pertussis is a highly contagious respiratory infection usually caused by the non motile, gram-negative coccobacillus Bordetella pertussis and, occasionally, by the related similar bacteria B. parapertussis and B. bronchiseptica. Characteristically, whooping cough produces an irritating cough that becomes paroxysmal and commonly ends in a high-pitched inspiratory whoop.

Since the 1940s, immunization and aggressive diagnosis and treatment have significantly reduced mortality from whooping cough in the United States. Mortality in children under age 1 is usually a result of pneumonia and other complications. The disease is also dangerous in the elderly but tends to be less severe in older children and adults. Since the 1980s reported cases of pertussis in the U.S. has increased.

Causes of Pertussis :

Whooping cough is usually transmitted by the direct inhalation of contaminated droplets from a patient in the acute stage; it may also be spread indirectly through soiled linen and other articles contaminated by respiratory secretions.

Whooping cough is endemic throughout the world, usually occurring in late winter and early spring. In about 50% of cases, it strikes unimmunized children under age 1, probably because women of childbearing age don't usually have high serum levels of B. pertussis antibodies to transmit to their offspring.

Signs and symptoms

After an incubation period of about 7 to 10 days, B. pertussis enters the tracheobronchial mucosa, where it produces progressively tenacious mucus. Whooping cough follows a classic 6-week course that includes three stages, each of which lasts about 2 weeks.

First, the catarrhal stage characteristically produces an irritating hacking, nocturnal cough; anorexia; sneezing; listlessness; infected conjunctiva and, occasionally, a low-grade fever. This stage is highly communicable.

After 7 to 14 days, the paroxysmal stage produces spasmodic and recurrent coughing that may expel tenacious mucus. Each cough characteristically ends in a lond, crowing inspiratory whoop, and choking on mucus causes vomiting. (Very young infants, however, may not develop the typical whoop.) Paroxysmal coughing may induce such complications as nosebleed, increased venous pressure, periorbital edema, conjunctival hemorrhage, hemorrhage of the anterior chamber of the eye, detached retina (and blindness), rectal prolapse, inguinal or umbilical hernia, seizures, atelectasis, and pneumonitis. In infants, choking spells may cause apnea, anoxia, and disturbed acid-base balance. During this stage, patients are highly vulnerable to fatal secondary bacterial or viral infections. Suspect such secondary infection (usually otitis media or pneumonia) in any whooping cough patient with a fever during this stage, because whooping cough itself seldom causes fever.

During the convalescent stage, paroxysmal coughing and vomiting gradually subside. However, for months afterward, even a mild upper respiratory tract infection may trigger paroxysmal coughing.

Central nervous system complications are uncommon but one should be aware of these. Seizures and encephalopathy may be seen. The mechanisms may include hypoxia or a toxin.

Diagnosis of Pertussis:

Classic clinical findings, especially during the paroxysmal stage, suggest this diagnosis; laboratory studies confirm it. Nasopharyngeal swabs and sputum cultures show B. pertussis only in the early stages of this disease; fluorescent antibody screening of nasopharyngeal smears provides quicker results than cultures but is less reliable. In addition, the white blood cell (WBC) count is usually increased, especially in children older than 6 months and early in the paroxysmal stage. Sometimes, the WBC count may reach 175,000 to 200,000/ul, with 60% to 90% lymphocytes.

Other conditions to rule out are adenovirus infections, tuberculosis, bronchitis, and influenza.

Treatment of Pertussis:

Vigorous supportive therapy requires hospitalization of infants (commonly in the intensive care unit), and fluid and electrolyte replacement. Other measures include adequate nutrition, codeine and mild sedation to decrease coughing, and oxygen therapy in apnea. Antibiotics, such as erythromycin and, possibly, ampicillin, must be initiated during the catarrhal phase of the illness to be effective in eliminating the infection. Antibiotics are also helpful in shortening the period of communicability and preventing secondary infections. Corticosteroids, especially in infants, may reduce the severity and course of illness.

Because very young infants are particularly susceptible to whooping cough, immunization-most commonly with the diphtheria- tetanus acellular pertussis (DTaP) vaccine - begins at 2, 4, and 6 months. Boosters follow at 18 months and at 4 to 6 years. The risk of pertussis is greater than the risk of vaccine complications such as neurologic damage. However, seizures or unusual and persistent crying may be a sign of a severe neurologic reaction and the doctor may not order the other doses. The vaccine is contraindicated in children over age 6 because it can cause a severe fever.

Special considerations and prevention tips of Pertussis:

1. Whooping cough calls for aggressive, supportive care and respiratory isolation (masks only) for 5 to 7 days after initiation of antibiotic therapy.

2. Monitor acid-base, fluid, and electrolyte balances.

3. Carefully suction secretions, and monitor oxygen therapy. Remember: sectioning removes oxygen as well as secretions.

4. Create a quiet environment to decrease coughing stimulation. Provide small, frequent meals, and treat constipation or nausea caused by codeine.

5. Offer emotional support to parents or children with whooping cough.

6. To decrease exposure to organisms, change soiled linen, empty the suction bottle, and change the trash bag at least once each shift.

Stress to parents the importance of correct immunization of infants, toddlers, and older children to increase protection against infection.