Parapertussis

Etiology and pathogenesis

Parapertussis (ICD-10: A37.1) is caused by a small gram-negative bacterium — Bordetella parapertussis. Unlike the classical pertussis pathogen, this bacillus produces a less potent exotoxin, which accounts for the relatively mild course of the disease.

The infection enters the body through the mucous membranes of the upper respiratory tract. The pathological process involves the respiratory tract, including the larynx, bronchi, bronchioles, and pulmonary alveoli. Sometimes the inflammation extends to the peribronchial tissue.

Epidemiology

The disease is transmitted by airborne droplets (aerosols). The source of infection is a sick person with clinical manifestations, less commonly an asymptomatic bacterial carrier.

• Contagiousness index: approximately 40%.
• Period of contagiousness: does not exceed 2 weeks.
• Outbreak pattern: the infection is characterized by periodic outbreaks, especially in organized childcare settings (kindergartens).
• Risk groups: children aged 2 to 7 years.

Clinical presentation

The incubation period lasts from 7 to 15 days. The disease runs a mild course without a pronounced intoxication syndrome; fever is typically absent. Patients generally feel well.

The leading feature is respiratory tract involvement in the form of tracheobronchitis. The main symptom is a cough, which can last from 2 to 4 weeks. Pertussis-like spasms with whoops and vomiting are rare.

Two main forms are distinguished based on the character of the cough:

1. Typical — with pertussis-like paroxysms.
2. Atypical — with ordinary tracheobronchial cough.

Diagnostics and treatment

The diagnosis is established based on laboratory tests, taking the epidemiological history into mandatory account. Complete blood count changes are nonspecific, but moderate leukocytosis with lymphocytosis is possible.

Diagnostic methods:

• Bacteriological (primary) — isolation of the pathogen culture.
• Serological (supportive) — indirect hemagglutination, complement fixation, and agglutination assays. The antibody titer rises starting from the 2nd week, peaking by weeks 3–4. However, due to cross-agglutination with pertussis, these tests are reliable only when combined with bacterial culture.

The prognosis for parapertussis is favorable. Mild forms do not require drug therapy. For moderately severe cases, treatment is administered as in pertussis.

Prevention and anti-epidemic measures

Specific vaccination against parapertussis is not performed.

Measures in the infection focus:

• Isolation of patients: standardly for 15 days (for children under 1 year — for 25 days).
• Contacts: children under 1 year are subject to a 14-day quarantine. Children over one year of age and adults are not subject to isolation.

Class and exam questions

What else to study on this topic

• Differential diagnosis of parapertussis and acute respiratory infections (RSV, metapneumovirus, mycoplasma)
• Features of the clinical course of pertussis and its typical complications
• Principles of treatment for moderately severe forms (by analogy with pertussis)
• Differential diagnosis with nonspecific bronchitis and foreign body aspiration

Other topics from the section «Chapter 12. Infectious and parasitic diseases»

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