Legionellosis in children (Legionnaires' disease, Pontiac fever): causes, symptoms, diagnosis, treatment

Legionellosis (Legionnaires' disease, Pontiac fever) is an acute infectious disease of bacterial etiology with fever, respiratory syndrome, lung damage, and often the gastrointestinal tract, central nervous system and kidneys.

ICD-10 code

• A48.1 Legionnaires' disease.
• A48.2 Legionnaires' disease without pneumonia (Pontiac fever).

Epidemiology of legionellosis

Legionella live in warm open water bodies overgrown with algae. In addition, they survive for a long time and multiply in water supply and air conditioning systems, cooling towers, showers, baths for balneotherapy, medical equipment for inhalation and artificial ventilation of the lungs.

The infection is always transmitted by airborne dust. Both air and water (condensate in air conditioners) can act as mediators of transmission of the pathogen. Other mediators of transmission can be shower heads, dust raised during excavation work, soil in endemic foci. Transmission of infection from person to person is unlikely. Infection of children can occur in preschool institutions, schools, orphanages and other premises with faulty air conditioners. Intrahospital outbreaks of legionellosis have been described, which gives grounds to consider this disease as a nosocomial infection.

The incidence is recorded as epidemic outbreaks or sporadic cases, mainly in the summer-autumn period. People of all ages, including infants, are ill.

Classification

A distinction is made between pneumonic form, catarrh of the upper respiratory tract, and acute febrile diseases with exanthema.

Causes of Legionellosis

The causative agent is Legionella, from the Legionellaceae family - a gram-negative rod, comprising more than 35 species: L. pneumophila, L. bozemanii, L. micdadei, etc. The L. pneumophila species is the most numerous, its representatives are divided into 15 serogroups, and each of them can cause disease in humans. To grow the pathogen, artificial nutrient media with the addition of L-lecithin and iron pyrophosphate (Müller-Hinten medium), as well as chicken embryos, are used.

Pathogenesis of legionellosis

The primary localization of the infection is the mucous membrane of the upper respiratory tract (in respiratory legionellosis) or lung tissue (in the pneumonic form), where the pathogen accumulates with the development of an inflammatory process. The further development of the disease depends on the dose and pathogenicity of the pathogen, previous sensitization, and most importantly, on the local and general resistance of the body.

Symptoms of Legionellosis

The incubation period for legionellosis is from 2 to 10 days.

The pneumonia form of legionellosis begins acutely with a rise in body temperature, chills, muscle pain and headaches. Dry cough, runny nose, chest pain during coughing appear from the first days. These symptoms progress over 3-5 days, body temperature reaches a maximum (39-40 °C), symptoms of intoxication are expressed, the cough becomes wet with expectoration, shortness of breath increases. Percussion in the lungs reveals foci of shortening of the percussion sound, and auscultation in the projection of these foci against the background of weakened breathing reveals crepitating and fine-bubble moist rales. The radiograph reveals focal shadows with a tendency to merge and form extensive darkening zones. In rare cases, pleurisy or minor exudation into the pleural cavity is possible.

In the peripheral blood there is leukocytosis, a neutrophilic shift, a tendency towards thrombocytopenia and lymphopenia, a sharp increase in ESR.

Legionella-type catarrh of the upper respiratory tract is practically indistinguishable from viral ARI: body temperature rises to 38-39 °C, cough, runny nose, chills are noted. Muscle pain, vomiting, loose stools, neurological symptoms are possible. Recovery occurs 7-10 days after the onset of the disease. There is evidence that the number of forms of legionellosis of the ARI type exceeds the number of forms with damage to the lung tissue by tens of times.

Acute febrile diseases with exanthema (Fort Bragg fever) are characterized by an increase in body temperature, catarrh of the respiratory tract and maculopapular rashes all over the body.

Diagnosis of legionellosis

Legionellosis can be suspected if darkened areas or spotted interstitial infiltrates are detected in the lungs, which have existed for a long time and often progress, despite active treatment with antibacterial drugs from the penicillin group.

For laboratory confirmation, the patient's material is sown on Mueller-Hinton agar with the addition of iron salts and L-cystine, or guinea pigs are infected with subsequent infection of chicken embryos. As an express diagnostic, the direct immunofluorescence method is used, with the help of which it is possible to detect the pathogen directly in sputum, bronchial washings or in biopsy prints of the bronchi and lungs obtained during bronchoscopy.

For serological diagnostics, ELISA, indirect immunofluorescence method or microagglutination reaction are used.

Differential diagnostics

The pneumonia form of legionellosis must be differentiated from severe pneumonia caused by viral-bacterial associations, chlamydia and mycoplasma.

Legionellosis cases of respiratory tract catarrh are differentiated from acute respiratory viral infections. Correct diagnosis in all cases is possible only on the basis of laboratory research results.

Treatment of legionellosis

Antibiotics are used as etiotropic treatment. The best effect is achieved when prescribing macrolides in combination with probiotics (Acipol, etc.).

Pathogenetic and symptomatic treatment is carried out according to generally accepted principles.

Prevention of legionellosis

Quarantine measures are ineffective. What is crucial is the examination of the water in the air conditioning system and disinfection by raising the water temperature to 60 °C, which allows the system to be cleared of legionella.

To prevent nosocomial legionellosis, it is necessary to thoroughly clean and sterilize medical equipment, especially devices used in the treatment of respiratory diseases (cannulas, tracheotomy tubes, ventilators).

Active immunization using vaccine preparations is currently being developed.

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