Pertussis, also known as whooping cough is an upper respiratory tract infection usually caused by the gram-negative bacteria, Bordetella pertussis. It is characterised by a severe prolonged cough. In fact, in China it is referred to as the 100-day cough as it can last so long.
It is highly contagious and is a notifiable disease in the UK.
🏘️ Epidemiology
In the UK there are approximately 1000 cases each year. This is due to the introduction of the vaccine (DPT vaccine).
Prior to the vaccine, it was one of the most common childhood diseases.
Pathophysiology
Bordetella pertussis is highly infectious and spreads easily between individuals. It is transmitted via respiratory droplets from sneezing and coughing, or it can be transmitted via fomites infected by respiratory secretions.
The incubation period is 7-10 days on average, after which the cough and symptoms begin. Transmission is most common in the first 1-2 weeks of infection, but can last until 2-3 week after the onset of the cough.
Once acquired, the bacteria adhere to ciliates respiratory epithelia. They then begin to produce the pertussis toxin which leads to ciliary paralysis, local damage and inflammation. The toxin also interferes with cytokines, for example by stimulating IL-10 which inhibit is macrophage activation.
The infection may result in pertussis pneumonia.
Infection also elicits an immune response, but immunity is not permanent and therefore vaccination is recommended.
There are 3 phases to pertussis:
- Catarrhal phase
Catarrh is the build-up of mucous due to inflammation of mucous membranes.
This phase lasts 1-2 weeks and symptoms are very similar to a viral upper RTI.
- Paroxysmal phase
The cough increases in severity, especially at night and after eating.
Infants may have an inspiratory whoop and apnoeic spells.
Persistent coughing can lead to subconjunctival haemorrhages or anoxia (causing syncope and seizures).
This phase last 2-8 weeks.
- Convalescent phase
The cough begins to subside over weeks to months.
😷 Presentation
- Cough
- Inspiratory whoop - paroxysmal coughing ending in a high-pitched inspiratory whoop. It typically begins at the second week of symptoms and persists for 1-6 weeks. More prevalent in children.
- Coryzal symptoms - such as rhinorrhoea, sneezing, low-grade fever.
- Post-tussive vomiting - the production of thick mucous that may be brought up when coughing can induce a reflexive vomiting.
- Facial erythema - more common in adults.
- Apnoeic spells in babies - these are short pauses in breathing.
🔍 Investigations and criteria
We may suspect whooping cough in a patient that has had an acute cough lasting >14 days without any other apparent cause, and has 1 or more of the following:
- Paroxysmal cough
- Inspiratory whoop
- Post-tussive vomiting
- Undiagnosed apnoeic spells in young infants
🏆 NICE states that to confirm diagnosis we can any of the following tests:
- Pernasal swab cultures
- PCR - using the pernasal swab.
- Serology - detection of anti-pertussis toxin IgG in the absence of vaccination in the past year.
🧰 Management
- Notify the Local Health Protection Team
- Antibiotics
- 🥇 Clarithromycin/azithromycin/erythromycin - if the cough is within the last 21 days. If the antibiotics are started late, they may not alter the disease course. They may still help in minimising transmission.
- Erythromycin should be offered to pregnant women over other macrolides.
- 🥈 Co-trimoxazole (bactrim) - if macrolides are contraindicated.
- Antibiotic prophylaxis should be provided to household contacts.
- School exclusion for 48 hours after commencing antibiotics.
The DPT vaccine is a part of the routine immunisation schedule in the UK.
It is also offered to women at 16-32 weeks of pregnancy to reduce the risk of newborn pertussis.
🚨 Complications
- Babies <6 months
- Dehydration
- Bronchiectasis
- Pneumonia
- Seizures
- Adults
- Epistaxis
- Subconjunctival haemorrhage
- Hernias
- Bronchiectasis