Whooping cough

Question 1

What are the differentials for child with persistent cough and poor feeding?

Answer 1

Bronchiolitis (RSV most commonly) 
Whooping cough 
Tonsillitis 
Allergic or infectious sinusitis 
Pneumonia 
Inhaled foreign body

Question 2

What is whooping cough? Why is there lymphocytosis?

Answer 2

It is an infection by anaerobic Bordetella Pertussis.

It can be characterised by one or more:

• Paroxysmal coughing
• Inspiratory whoop without another cause
• Post-pertussive vomits
• Persistent coughing lasting more than 2 weeks

Pertussis toxin reduces lymphocyte entry into lymph nodes.

Question 3

What are the stages of the illness?

Answer 3

Incubation period

1. Catarrhal: 1-2 weeks
2. Paroxysmal: 1-6 weeks
3. Convalescence: up to 1 month

Question 4

What is the causative agent and its characteristics?

Answer 4

Whooping cough is caused by Bordetella Pertussis, an aerobic coccobacillus.

It has fimbria which blocks cell signalling to lymphocytes, and it can enter and survive within phagocytic leucocytes and non-phagocytic cells.
Diagnosis is difficult in catarrhal stage.

Question 5

What is the pathogenesis of whooping cough?

Answer 5

The bacteria is transferred by air-borne respiratory droplets. The organism produces biologically active virulence factors that promote cellular attachment, causing local tissue damage and interfere with host defences.

After inhalation, it adheres to the respiratory epithelium of the URT via protein adhesins.

After adhering, it induces local tissue damage by tracheal cytotoxin, leading to loss of respiratory cells leading to cough.

Organisms can be found intracellularly within alveolar macrophages as well as ciliated respiratory epithelial cells, which explains the prolonged duration of the cough.

Question 6

What is the clinical course of whooping cough?

Answer 6

The incubation period: 7-10 days
Catarrhal period: 1-2 weeks
Paroxysmal period: 2-8 weeks (coughing becomes high-pitched whoop)
Convalescent period: 1-2 weeks

Question 7

What is the first, second and third line treatment for whooping cough?

Answer 7

First-line: azithromycin
Second-line: trimethoprim + sulphomethoxazole.
Third-line: clarithromycin

Question 8

What supportive therapy would you provide the patient?

Answer 8

• Hospitalisation if they are at respiratory distress
• Fluids and nutrition
• RR, HR, O2 sat, WBC of infants should be monitored
• Macrolide ABx

Question 9

Where is pertussis on the Australian immunisation schedule??

Answer 9

As part of DTPa at 2,4,6 months, 18 months, 4yrs, 10-15yrs, and during pregnancy.

Question 10

How would you culture Bordetella pertussis?

Answer 10

• Use special polyester or calcium alginate swab
• Promptly transport/inoculate agar
• One example of valid agar: Regan-Lowe agar (charcoal blood (neutralises fatty acids which are toxic to b pertussis) + cephalexin (inhibits normal flora) + horse blood (nutrients)