Pertussis (Whooping Cough)

Key Features

Essentials of Diagnosis

• Prodromal catarrhal stage (1–3 weeks) characterized by mild cough and coryza, but without fever

• Persistent staccato, paroxysmal cough ending with a high-pitched inspiratory "whoop"

• Leukocytosis with absolute lymphocytosis

• Diagnosis confirmed by PCR or culture of nasopharyngeal secretions

General Considerations

• An acute, highly communicable infection of the respiratory tract caused by Bordetella pertussis characterized by severe bronchitis

• Children usually acquire the disease from symptomatic family contacts

• Bordetella parapertussis and Bordetella holmesii cause a similar but milder syndrome.

Demographics

• Cases have increased in the United States since 2000

• In 2007, about 10,000 cases were reported; increased to more than 16,000 cases in 2009, and 48,277 cases in 2012

Clinical Findings

Symptoms and Signs

• Onset is insidious, with catarrhal upper respiratory tract symptoms (rhinitis, sneezing, and an irritating cough)

• Slight fever may be present; temperature > 38.3°C suggests bacterial superinfection or another cause of respiratory tract infection

• After about 2 weeks, cough becomes paroxysmal, characterized by 10–30 forceful coughs ending with a loud inspiration (the whoop)

• Vomiting commonly follows a paroxysm

• Coughing is accompanied by cyanosis, sweating, prostration, and exhaustion

Differential Diagnosis

• Bacterial, tuberculous, chlamydial, and viral pneumonia

• Cystic fibrosis

• Foreign body aspiration

• Adenoviruses

• Respiratory syncytial virus

Diagnosis

Laboratory Findings

• WBC counts of 20,000–30,000/μL with 70–80% lymphocytes typically appear near the end of the catarrhal stage; and the degree of lymphocytosis correlates with the severity of disease

• Severe pulmonary hypertension and hyperleukocytosis (> 70,000/μL) are associated with severe disease and death in young children with pertussis

• Many older children with mild infections never demonstrate lymphocytosis

• Identification of B pertussis by culture or PCR from nasopharyngeal swabs or nasal wash specimens proves the diagnosis

Imaging

• Chest radiograph reveals thickened bronchi and sometimes shows a "shaggy" heart border

Treatment

General Measures

• Nutritional support during the paroxysmal phase is important

• Frequent small feedings, tube feeding, or parenteral fluid supplementation may be needed

• Minimizing stimuli that trigger paroxysms is probably the best way of controlling cough

Specific Measures

• Antibiotics may ameliorate early infections but have no effect on clinical symptoms in the paroxysmal stage

• Azithromycin is the drug of choice because it promptly terminates respiratory tract carriage of B pertussis. Azithromycin is often preferred due to ease of compliance and decreased gastrointestinal side effects

• Clarithromycin may also be used

• Erythromycin given 4 times daily for 14 days is acceptable but not preferred; has been associated with pyloric stenosis in infants younger than 1 month

• Ampicillin (100 mg/kg/d in four divided doses) ...