Bordetella pertussis

Bordetella pertussis

 

Pertussis is a highly infectious and contagious disease caused by Bordetella pertussis and is commonly referred to as whooping cough.

Epidemiology

  • Incidence – 1-5/100,000
  • Transmission
    • Adult and teenage children with common cold symptoms are significant reservoirs of the organism and source of outbreaks in highly susceptible populations (transmission rates >90% in susceptible populations)
      • Primarily seen in those with waning immunity to childhood vaccination
      • Immunity begins to wane during early adolescence
      • Secondarily seen in unimmunized infants
    • B. pertussis, transmitted by respiratory droplets, causes disease only in humans
    • Infection occurs most frequently in late spring and summer

Organism

  • Bordetella pertussis, a gram-negative pleomorphic coccobacillus
  • Produces multiple toxins that aid in organism attachment and production of disease
  • B. parapertussis is a related species that may cause a milder form of pertussis syndrome

Clinical Presentation

  • Nonspecific viral upper respiratory tract infection symptoms
    • Disease spread often not recognized due to mild symptoms in immunized persons
    • Secondary spread common in families and schools
  • After 7-10 day incubation, a prolonged course ensues which consists of 3 overlapping stages
    • Catarrhal (1-2 weeks)
    • Paroxysmal coughing (1-4 weeks)
    • Convalescent (4-6 weeks)
  • Partially immune persons and infants older than 6 months may not manifest all of the typical symptoms
    • Paroxysmal coughing may be absent
  • Classical pertussis generally diagnosed clinically
    • Paroxysmal cough
    • Inspiratory whoop
    • Posttussive vomiting
    • Lymphocytosis
  • Atypical pertussis may occur with mild or absent symptoms in adults or previously vaccinated children
    • Atypical pertussis is common, endemic and usually unrecognized in adults
  •  Secondary complications
    • Respiratory 
      • Pneumonia
      • Bronchitis
      • Laryngitis
      • Pneumothorax
    • Nonrespiratory
      • Complications as a result of severe cough
        • Rib fracture
        • Epistaxis
        • Subconjunctival hemorrhage
      • Central nervous system
        • Seizures
        • Encephalitis
        • Deafness
      • Hemolytic Uremic syndrome

Diagnosis

  • Indications for testing
    •  Patients with predominant complaint of cough, especially in the absence of fever, sore throat, hoarseness, tachypnea of wheeze
  • Laboratory testing
    • PCR
      • Highly sensitive and specific for pertussis – must use nasopharyngeal swab for highest sensitivity and specificity
      • Treatment reduces contagious phase in 5 days and may negate PCR results
    • Nasopharyngeal culture
      • Considered gold standard, but is frequently negative in adults
      • Recommended only during the first 3 weeks of illness
    • Serological testing 
    • Requires sequential specimens negating clinical utility of early serological diagnosis
    • Useful for epidemiology or when diagnosis is considered late in the course of the disease
    • Useful for evaluating response to pertussis vaccine

Click here for a chart of Comparison of Definitions for Pertussis Infection

Differential Diagnosis

  • Chlamydia pneumoniae
  • Adenovirus
  • Mycoplasma
  • Parainfluenza
  • Influenza
  • Asthma
  • Chronic bronchitis
  • Cytomegalovirus (CMV)

Treatment

  • Antibiotics
    • If treatment given after 3-4 days of symptoms only contagiousness is reduced
    • Prophylaxis for household contacts

Prevention

  • Vaccination
  • Pediatric age groups – combined Hib and DPT
  • Adult revaccination
    • During teen years and in patient 30 years and older (diphtheria, pertussis acellular and tetanus vaccine)

See Also