Pertussis

A highly contagious acute respiratory infection caused by Bordetella pertussis

Aetiology

• Causative agent: Bordetella pertussis

• Gram-negative coccobacillus

• Strictly human pathogen

• Produces multiple virulence factors:
• Pertussis toxin
• Filamentous hemagglutinin
• Adenylate cyclase toxin
• Tracheal cytotoxin

Clinical presentation

Catarrhal Stage (1–2 weeks)

• Mild upper respiratory symptoms:
• Rhinorrhea
• Sneezing
• Mild cough
• Low-grade fever

• Most contagious stage

• Often indistinguishable from common cold

Paroxysmal Stage (2–6 weeks)

• Severe paroxysms of coughing

• Inspiratory “whoop” (children)

• Post-tussive vomiting

• Apnea (infants)

• Cyanosis

• Minimal or no fever

Convalescent Stage (Weeks–months)

• Gradual reduction in cough frequency

• Cough may recur with subsequent URIs

Investigation

PCR (Preferred)

• Nasopharyngeal swab

• High sensitivity and specificity

• Best in early disease

Culture

• Gold standard but low sensitivity

• Requires special media (Bordet-Gengou, Regan-Lowe)

• Best during catarrhal stage

Serology

• Useful in later stages

• Detects anti-pertussis toxin antibodies

Hematology

• Marked absolute lymphocytosis (characteristic)

Management

Antibiotic Therapy

• Reduce transmission

• Limited effect on cough if started late

• Azithromycin
• <12 y.o → 10mg/kg/day SD for 5 days
• ≥12 y.o → 1st day 500 mg, then 250 mg to 5th day

• Clarithromycin
• <12 y.o → 15mg/kg/day divide to 2 dosage for 7 days (not recommended for <1 m.o)
• ≥12 y.o → 1gr/day divide to 4 dosages for 7 days

• Erythromycin
• <12 y.o → 40-50mg/kg/day divide to 4 dosages for 14 days
• ≥12 y.o → 2gr/day divide to 4 dosages for 14 days

• Trimethoprim-sulfamethoxazole (macrolide intolerance)

Supportive Care

• Oxygen if hypoxic

• Suctioning secretions

• Small, frequent feeds

• Hospitalization for infants <6 months or severe disease

Isolation

• Droplet precautions

• Isolate until 5 days of effective antibiotics completed