Pertussis A37.9

Acute bacterial infectious disease in children with a barking, seizure-like cough and possibly subsequent vomiting caused primarily by Bordetella pertussis. Bordetella pertussis is present worldwide. Less commonly, infections with B. parapertussis or B. holmesii can also lead to a whooping cough-like clinical picture, but the course is usually milder and shorter than that of infection by B. pertussis. In 2015-2018, 3-4% of transmitted pertussis cases were caused by B. parapertussis; in 2019, this proportion increased to 9% (RKI data).

Bordetella pertussis is a small gram-negative, immobile, encapsulated, coccoid, aerobic rod. It produces a variety of toxins and virulence factors. On the surface of the bacterium are outer membrane proteins, fimbriae and lipopolysaccharides.

Pertussis occurs year-round, with a slightly higher incidence in autumn and winter than in the rest of the year. Similar to other Western countries, Germany continues to see cyclical increases in pertussis at 4- to 6-year intervals despite high vaccination rates among younger children - in 2018, the vaccination rate for school-beginners was approximately 93%. Since the introduction of the nationwide pertussis reporting requirement in 2013, between 11 and 20 cases (Erkr.) per 100,000 inhabitants (Einw.) have been reported annually to the RKI nationwide according to the Infection Protection Act (Infektionsschutzgesetz, IfSG). Infants are most affected in epidemic years, with incidences of more than 100 ill./100,000 inhabitants, and often require hospital treatment. Therefore, the STIKO 2020 has recommended pertussis vaccination for women during pregnancy (see below).

Due to a rapid decline in immune protection after vaccination, pertussis illnesses also occur in older children and adolescents.

Although the incidence is lower in adults,approximately 60% of all cases now occur in persons ≥ 18 years of age. This is due to insufficient implementation of the recommended booster vaccinations, especially in adolescents and adults.

The clinical picture is classically divided into 3 stages:

I. Stage catarrhale: Symptoms of an unspecific infection of the upper respiratory tract dominate (rhinitis, mild cough), fever, however, rather speaks against the diagnosis. Duration approx. 1-2 weeks.

II. stage convulsivum: Seizure-like coughing episodes (so-called staccato cough) dominate the clinical picture, followed by inspiratory wheezing or whooping. Frequently, regurgitation of viscous mucus and/or vomiting is also observed in association with the coughing attacks. Fever is also atypical at this stage and may indicate a secondary bacterial infection. Duration 4-6 weeks.

III. stage decrementi: Gradual resolution of the above symptoms. Duration 6-10 weeks.

Skin manifestations include traumatic mucosal ulceration of the lingual frenulum and hemorrhages. Also: subconjunctival petechiae, nasal and gingival hemorrhages, possibly a necrotizing leukocytoclastic vasculitis.

Since the symptoms are often not typical, especially in adult patients, laboratory diagnostics are crucial for establishing the diagnosis. This should be performed if ...

1. typical symptoms are present (cough attacks, followed by inspiratory stridor or vomiting) or
2. contact with a confirmed case of pertussis has occurred or
3. Cough persists for more than 14 days.

Within the first 2-3 weeks after symptom onset, serology is not informative.

At this stage, a deep nasopharyngeal swab with direct pathogen detection by culture or PCR is suitable.

After about 3 weeks, IgG antibodies against Bordetella pertussis(PT IgG antibodies) can be detected serologically by ELISA, and confirmation by detection of specific IgA antib odies can be performed for nondiagnostic titers (gray range). IgM antibodies against Bordetella pertussis are not informative.

Reference values for PT-IgG antibodies:

• PT-IgG ≥ 100 IU/ml: Indicates recent pathogen contact.
• PT-IgG ≥ 40 and <100 IU/ml: gray range
• PT-IgG < 40 IU/ml: no indication of recent pathogen contact

The most common complication is pneumonia, usually caused by superinfection with other bacterial pathogens, especially pneumococci or unencapsulated Haemophilus influenzae. Pneumonia affects up to 10% of ill infants and the elderly, and is less common in older children and younger adults (Hof H et al.2019). Other complications: otitis, sinusitis, incontinence, hernia, rib fracture, and subconjunctival hemorrhage (De Serres G et al.2000; Heininger U et al.1997).

Rare neurologic complications may include cerebral seizures and encephalopathies .

The cause of death in infants is often hyperleukocytosis with up to 100,000/mm3, resulting in severe hypoxemia and pulmonary hypertension (Liese JG et al. 2013).

In principle, antibiotic therapy can only influence the duration and severity of cough attacks if it is administered as early as possible (i.e. before the onset or in the first 1-2 weeks from the onset of the cough). However, it may be important in breaking the chains of infection. Thus, the use of antibiotics is only useful as long as the patient excretes bordetella (positive pathogen detection in nasopharyngeal secretions by culture or PCR, or usually from the end of the incubation period in the catarrhale stage up to three weeks (in infants also up to 6 weeks) after the onset of the convulsivum stage).

Erythromycin has proven effective. However, the macrolides azithromycin and clarithromycin are equally effective (Herzig P et al. (1998)) and are the drugs of choice today because of their better tolerability and simpler application. Macrolide resistance has been observed only very rarely. Cotrimoxazole can be used as an alternative to macrolides.

Oral penicillins and cephalosporins are not suitable for eradicating B. pertussis in the nasopharynx.

From today's perspective, eradication of pertussis is not possible. Due to the limited duration of immunity both after natural disease and after complete vaccination, each person can become reinfected and ill several times in their lifetime. The goals of the current vaccination strategy in Germany are therefore the earliest possible and complete vaccination protection for infants and young children who are particularly at risk from B. pertussis (basic immunization). In addition, booster immunization is necessary in preschool and adolescent age as well as in adults to maintain the clinical efficacy of the vaccine protection and to minimize transmission to unvaccinated and non-immune individuals.

Note: Legal basis (obligation to report according to IfSG): According to § 6 Abs. 1 Nr. 1 IfSG, the public health department is notified by name of suspected illness, illness as well as death from pertussis and according to § 7 Abs. 1 IfSG of direct or indirect evidence of Bordetella pertussis and Bordetella parapertussis, as far as it indicates an acute infection.

The reports must be submitted to the public health department no later than 24 hours after they become known.

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