The number of registered whooping cough cases this year is much higher than it was at the same time last year. After a longer break due to the COVID protection measures, case numbers now return to their pre-pandemic levels in many countries.
In Germany, another temporary trend was observed: For 2022/2023 the Robert-Koch-Institut (RKI) notes that there was a significant increase in whooping cough cases not caused by the typical pathogen, Bordetella (B.) pertussis, but by B. parapertussis. These case numbers even exceed pre-pandemic levels. According to the RKI data, the pathogen’s share increased from under 10 to more than 50 percent of cases. Some potential reasons for the increase:
- Catch-up effect: fewer immune people after the COVID pandemic
- Changed diagnostic procedures: increased detection of parapertussis due to more widespread multiplex PCR testing
- Vaccination deficit: delayed approximation of case numbers due to an uneven immunisation against the two Bordetella species (sufficiently effective vaccination only against pertussis)
However, according to recent figures of the RKI, this trend has not continued in 2024 and the share of B. parapertussis infections returned to below 10 percent. https://survstat.rki.d
About whooping cough
Whooping cough is a highly contagious respiratory infection, which is most frequently caused by the bacterial species B. pertussis and less frequently by B. parapertussis. It is spread between humans via droplets.
Despite overall high vaccination rates (against B. pertussis), the disease remains one of the leading causes of vaccine-preventable deaths worldwide. Unvaccinated or incompletely vaccinated babies under one year of age are most at risk of serious illness and death. In 2018, the World Health Organization (WHO) reported 151,074 whooping cough cases globally and estimated that there were 89,000 deaths due to the disease.
Following B. pertussis infection, the first symptoms appear after an incubation time of approximately 7–14 days. The disease is typically divided into 3 stages:
- Catarrhal stage: Mild flu-like symptoms with moderate fever; approx. 1–2 weeks
- Convulsive stage: Characteristic coughing fits (“staccato” cough) that frequently occur at night and feature the typical “whoop” sound, often with vomiting of mucus; approx. 4–6 weeks
- Convalescent stage: Abating of the cough; approx. 6–10 weeks
The typical whooping cough symptoms are mainly observed in children. In adolescents and adults, however, the disease manifests as ongoing cough without the typical coughing fits, making laboratory diagnostics crucial for diagnosis.
Diagnostics
In early stages of the disease, the direct pathogen detection by means of culture or PCR from nasopharyngeal smears is useful for the diagnosis of a Bordetella infection. From the convulsive stage, the pathogen is usually no longer detectable in the respiratory tract, which means that serology plays an important role.
For specific detection of antibodies against B. pertussis, ELISAs on the basis of pertussis toxin (PT) are recommended. In contrast to other Bordetella antigens such as filamentous haemagglutinin (FHA), PT is only produced by B. pertussis, which makes it a highly specific antigen and important in serological diagnostics.
EUROIMMUN offers different test systems for whooping cough diagnostics:
Direct detection
In acute infections, the real-time PCR assay GeneProof Bordetella pertussis/parapertussis PCR Kit* for the detection of specific nucleic acid sequences of B. pertussis and B. parapertussis delivers fast and precise results to enable early and targeted treatment.
Antibody detection
The Anti-Bordetella pertussis Toxin ELISA (IgG) and the Anti-Bordetella pertussis Toxin ELISA (IgA) are based on native, highly purified PT as the target antigen. Cross reactions with B. parapertussis are therefore excluded. Both ELISAs allow quantification of the antibody titer in international units (IU/ml) according to the WHO standard.
Two more ELISAs are on offer, which use native, highly purified Bordetella FHA as the antigen and thus allow sensitive detection of both B. pertussis and B. parapertussis infections.
Detection of anti-PT IgA as well as anti-FHA IgA and IgG is particularly useful for diagnosis in case of unclear anti-PT IgG titers of 40 to 100 IU/ml.
Furthermore, the line blot EUROLINE Bordetella pertussis (IgG) enables parallel qualitative detection of IgG antibodies against PT, FH and adenylate cyclase toxin (ACT).
Automation
To streamline the laboratory routine, EUROIMMUN offers flexible automation solutions for processing of the test systems, which suit different throughputs and laboratory-specific requirements.
INFO: An immune response following vaccination cannot be distinguished from one following infection. Reliable interpretation of results after vaccination with acellular pertussis vaccines can only be achieved after around a year.
* Product manufactured by GeneProof