Medical Fun Facts Podcast

MFF0075: Bordetella Part II

t’s Monday 17 July 2017.

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Last week I started on pertussis or whooping cough. I looked at the symptoms it causes and the relevance of immunisation to preventing the disease.

Tonight, I want to mention diagnosis and antimicrobial treatment.

Diagnosis is usually based on a clinical suspicion, especially if the cough is typical and the patient is a child. In adults, getting clinical clues can be more difficult and it’s always important to ask about family and friends who may be ill with a cough. Not surprisingly, a story about an infected infant connected by one or two degrees of separation isn’t uncommon.

Bordetella pertussis can be cultured from nasopharyngeal specimens during the catarrhal and the early paroxysm stages of the disease. Unfortunately, culture has poor sensitivity when compared with newer techniques like polymerase chain reaction or PCR.

In the old days, we used to use cough plates which we would prepare and send to GPs’ surgeries and to collection centres.

Serology can also be performed but serological test results should be interpreted carefully. It’s not possible to differentiate between disease and vaccination when antibodies to Bordetella pertussis have been detected.

The rate of whooping cough in the community is dependent on the rate of vaccination. In well-vaccinated groups with good nutrition and available medical care, rates of disease tend to be low. As vaccination rates wane because of complacency and when parents and guardians elect not to vaccinate, the rates of disease rise and sometimes to levels where there is enough infection for deaths to occur.

Patients diagnosed with pertussis should be isolated until they have received five days of antimicrobial treatment after which the patient will no longer be contagious.

Treatment with antimicrobials is important, not so much to shorten the duration of coughing but to help inhibit the spread of the infection.

Treatment is usually with a macrolide like erythromycin, clarithromycin or azithromycin.

If treatment can be given during the catarrhal stage and before the paroxysms start, the disease may be truncated.

Whooping cough is an awful disease which can create significant suffering in children and adults alike and which is a definite cause of death. In most situations, infection can be prevented by adequate vaccination as part of population health measures.

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