Introduction

This is a 2-part blog on Bordetella pertussis (B. pertussis) a disease also known as whooping cough. Part 1 will talk about the pathophysiology and management of B. pertussis, whereas part 2 will talk about the ethics surrounding the case study. I really enjoyed this case study, especially when ethics are involved. This is part 1 with a focus on pathophysiology and management.

Whooping cough, B. pertussis, is an extremely contagious bacteria that is transmitted through air droplets or physical contact (1). The outcome of getting whooping cough may cause deaths in high-risk groups such as infants (1-3). After numerous trials between 1923-1924, the vaccine proved to have some protection, and by the early 1940s, the vaccine was widely distributed and endorsed by the American Academy of Paediatrics (4). The vaccine proved to be effective in reducing deaths (1,3,4); however, childhood immunisation is a delicate topic to those who are opposed especially when it involves a child’s autonomy as well as the parents’ rights. There are many ethical issues regarding vaccines and infants as they cannot give adequate consent and have to rely on the parents. Approaching this challenge may be difficult and tedious, and often healthcare professionals may approach this topic with too much information or emotions. Building rapport and communication regarding parents who are against vaccination is key in managing the issues.

Janet, a mother, has brought her 10-month-old infant into the hospital. She mentions that the baby has been unwell for several weeks, starting with what she thought was a cold, with a runny nose and dry cough. However, in the past two weeks, a more definite cough has developed, and the baby has had to be kept home from Day-care. When checking the baby’s history, you notice that he has not received his standard childhood immunisations. When you mention this to the Mum, she states that she is very “anti-vaccination due to all the toxic products that are included in vaccines today”. Tests confirm your suspicions that the baby has whooping cough.

Pathophysiology

Whooping cough, known as Bordetella pertussis, is a fastidious gram-negative bacteria and acts as a toxin-mediated disease (1,3). With an R0 of 15-17 (5), B. pertussis is extremely contagious and is spread by droplets in the air from coughing or sneezing, or can be done via physical contact for example, through hands that have been contaminated by the bacteria (1,3). The bacteria enter the lungs and attaches onto the cilia cells and paralyse the cilia cells through the release of toxins (1). Inflammation of the respiratory tract occurs, and the pulmonary secretion clearing is hindered and interfered (1). B. pertussis’ antigen manages to evade the immune system by impairing chemotaxis of the white blood cells even though lymphocytosis is promoted (1). Recent studies have demonstrated the presence of B. pertussis in alveolar macrophages (1).

B. pertussis’ incubation most common period ranges from 7-10 days (may be from 4-21 days) and its clinical course can be described into three stages (1,3). The first stage is known as the catarrhal stage where B. pertussis is not displaying apparent symptoms but instead vague infectious symptoms that are similar to a cold (1,3). These symptoms are coryza, low-grade fever, mild cough, sneezing (1,3). However, the cough will become more severe. After 1-2 weeks of the catarrhal stage, the second stage starts, which is known as paroxysmal (1). It is noteworthy that fever is generally not prominent throughout the disease (1).

The paroxysmal stage is where patients present with symptoms of bursts (paroxysms) of coughs that are rapid and numerous and describe difficulty in expelling mucus (1,3). At the end of an attack, patients will inspire with much effort where a high-pitch ‘whoop’ can be heard (1). The patient may become cyanosed and vomit along with exhaustion, which may occur after an attack (1). Infants are affected much worse than adults and may appear to be very sick (1-3). The paroxysmal attack can be seen more frequently at night and increase in frequency on week 2-3 and then gradually decreases (1). The paroxysmal stage can be between 1-6 weeks long but can go on for 10 weeks (1).

The last stage is known as the convalescent stage where recovery is gradual (1). The cough will disappear in 2-3 weeks, however other respiratory diseases may trigger paroxysm attacks long after the recovery stage (1). Adults and vaccinated children are partially protected and can still get B. pertussis, albeit in a mild progression of the disease or may be wholly asymptomatic but can still spread the disease (1-3,5). Hence, high-risk groups such as unvaccinated or partially vaccinated infants are susceptible. Patients with B. pertussis are infectious from the catarrhal stage to the third week of the paroxysmal stage or until 5 days of effective use of the antimicrobial treatment (1-3,6).

Complications of B. pertussis is secondary bacterial pneumonia, neurological complications and pneumothorax, which are the most worrying (1-3). Pneumonia is the commonest and the highest in terms of pertussis-related deaths, and infants are at the highest risks of developing complications (1-3). Data as shown that 11.8% of infants younger than 6 months of age develop pneumonia complications compared to 5.2% in all B. pertussis cases (1).

Management

Hospitalisation for this patient is unlikely, but close supervision should be carried out to notify any complications that may occur as the patient is in a high-risk group (1). Under 6-months are immediately hospitalised, and the same can be applied if the patient deteriorates and becomes unwell (1-3).

Timing with whooping cough is essential. It has been noted that treatment to which has been started 1-2 weeks before the paroxysmal stage (the catarrhal stage) lessens symptoms (1,3). The Centers for Disease Control and Prevention (CDC) strongly suggest clinicians to start treatment before the test results for patients who are in high-risk groups or prone to complications such as infants. Half of the infants less than 1 year of age need treatment at the hospital (2). Late diagnosis and treatment with the use of antibiotics will be ineffective and will not change the diseases’ outcome (1,3).

In the case above, the patient is described to be at the beginning of his third week of paroxysmal stage and could be at the end of the infectious stage. Nonetheless, the possibility of still being contagious is considerable. The CDC suggests that patients less than 1 year of age within 6 weeks of the onset of coughing should be treated with antibiotics, where the Royal Children’s Hospital Melbourne guidelines usually do not prescribe antibiotics after 3 weeks of the coughing onset. From the confirmation of the tests, patient’s history and symptoms, antibiotic treatment should be promptly started. The patient must also be isolated from others, especially high-risk groups.

The CDC mentions that close contacts that were exposed should also be started on antibiotics (7); this is called post-exposure antimicrobial prophylaxis (PEP). This is especially true in high-risk settings such as the Day-care, where the patients are also in high-risk groups. As a reminder for context, a patient can spread B. pertussis to potentially 15-17 other patients (from its R0)(5). The same antibiotics, schedule and dose should be used (6,7).

The antimicrobial of choice for treatment and chemoprophylaxis for patients of 1 month and older are azithromycin, clarithromycin and erythromycin (6). Trimethoprim-sulfamethoxasole may be used as an alternative for conditions where adverse effects are not tolerated, drug interaction, ease of adherence and cost (6). For children less than 1 month, macrolides should be used with caution as infantile hypertrophic pyloric stenosis (IHPS) has been associated (6). However, severe B. pertussis and its complications outweigh IHPS; hence macrolides should still be given as prophylaxis (6). The Food and Drug Administration (FDA) has issued a warning with azithromycin to change the electrical activity of the heart and caution needs to be taken with children who have congenital heart defects (6).

B. pertussis may rapidly progress in infants thus treat confirmed and suspected cases promptly with antibiotics as well as reporting B. pertussis to the local public health department for close contact tracing and preventing further cases (1,3,6). The CDC mentions in targeting PEP use to high-risk groups only (7). As such, household contacts even if they had B. pertussis immunisation must be given PEP within 21 days of the onset of coughing (7). Studies have shown that secondary attack rates are high within family members (7). Hence the patient’s mother, family members living in the same household and every child at the Day-care should be on PEP (7). People who are immunocompromised, pregnant, pre-existing conditions such as moderate to severe asthma at the Day-care and family should be closely monitored (6,7). Do not give PEP to low-risk groups and do not provide multiple rounds of antibiotics when there is a continued transmission patterned (7).

Manage clinical complications such as an antibiotic course for pneumonia, an intravenous line for dehydration and anorexia, selected seizure medications, oxygen for apnoea and encephalopathy resulting from hypoxia and treat pneumothorax, refractory pulmonary hypertension and rectal prolapses (1,6).

To manage other people surrounding our patient who has not been exposed, a vaccination reminder for catchups (boosters) or making sure everybody is at the expected course is recommended. The vaccine is for all ages where five DTap is given for young children (2 months to 6 years), and Tdap is for preteens, pregnant women and adults who have never received the vaccination (1,3,9,10). Advice the mother to take the vaccination as pertussis can be passed from mothers to children when they are born (1,3,9). The vaccination is the most effective way of preventing B. pertussis. 

Finally, lifestyle modifications can be suggested such as getting plenty of rest, drinking lots of fluids, eat smaller meals, have a fresh environment such as not tobacco smoke or irritants that may start a paroxysmal burst, hand hygiene and wear a mask for adults who have to leave the house but has been exposed to the patient (11).

Published 30th September 2020. Last reviewed 1st December 2021.

Reference

1.     Liang J, Weinbaum C, Moro P. Pertussis. In: Hamborsky J, Kroger A, Wolfe C, eds. Epidemiology and Prevention of Vaccine-Preventable Diseases. 13th ed. Washington, D.C.: Public Health Foundation; 2015:261-278. https://www.cdc.gov/vaccines/pubs/pinkbook/downloads/pert.pdf. Accessed September 12, 2020.

2.     The Royal Children's Hospital General Medicine and Respiratory and Sleep Medicine departments. Whooping cough. The Royal Children’s Hospital Melbourne. https://www.rch.org.au/kidsinfo/fact_sheets/Whooping_cough/. Reviewed April, 2019. Accessed September 12, 2020.

3.     World Health Organization authors. Pertussis. World Health Organization. https://www.who.int/immunization/monitoring_surveillance/burden/vpd/WHO_SurveillanceVaccinePreventable_16_Pertussis_R1.pdf?ua=1. Updated September 5, 2018. Accessed September 17, 2020.

4.     Cherry, JD. The History of Pertussis (Whooping Cough); 1906–2015: Facts, Myths, and Misconceptions. Curr Epidemiol Rep. 2015;2:120-130. https://doi.org/10.1007/s40471-015-0041-9.

5.     European Centre for Disease Prevention and Control. Expert consultation on pertussis. Barcelona: European Centre for Disease Prevention and Control; 2012:1-11. Available at: https://www.ecdc.europa.eu/sites/default/files/media/en/publications/Publications/pertussis-meeting-2012.pdf. Accessed September 12, 2020.

6.     Centers for Disease Control and Prevention authors. Treatment. Centers for Disease Control and Prevention. https://www.cdc.gov/pertussis/clinical/treatment.html. Reviewed October 25, 2019. Accessed September 15, 2020.

7.     Centers for Disease Control and Prevention authors. Postexposure Antimicrobial Prophylaxis. Centers for Disease Control and Prevention. https://www.cdc.gov/pertussis/pep.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fpertussis%2Foutbreaks%2Fpep.html.   

8.     Centers for Disease Control and Prevention authors. Postexposure Antimicrobial Prophylaxis. Centers for Disease Control and Prevention. https://www.cdc.gov/pertussis/pep.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fpertussis%2Foutbreaks%2Fpep.html. Reviewed November 18, 2019. Accessed September 15, 2020.

9.     Centers for Disease Control and Prevention authors. Whooping Cough Vaccination. Centers for Disease Control and Prevention. https://www.cdc.gov/pertussis/vaccines.html#clinical-information. Reviewed January 15, 2019. Accessed September 15, 2020.

10.  Centers for Disease Control and Prevention authors. Pertussis frequently asked questions. Centers for Disease Control and Prevention. https://www.cdc.gov/pertussis/about/faqs.html. Reviewed November 18, 2019. Accessed September 17, 2020.

11.  Mayo Clinic authors. Whooping Cough. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/whooping-cough/diagnosis-treatment/drc-20378978. Reviewed October 9, 2019. Accessed September 15, 2020.