Pertussis / Whooping Cough 

• infection by Bordetella pertussis – Gram negative coccobacillus
• droplet spread
• incubation period 7 days
• immunity not lifelong
  • up to 25% adult prolonged cough (1-4 weeks) due to pertussis
• characteristic two to fiveyear cyclic pattern of epidemics
  1. in 2009 153 cases per 100,000 population
     1. 0-4 year age group 22%
     2. < 6 months 3%
     3. 59 year age group 15%
     4. 3 infant deaths
• most common vaccine preventable illness
  1. catchup vaccinations for children and adults introduced in 2004
  2. ‘cocooning’ strategy (vaccinating close contacts of infants to reduce the likelihood of exposure introduced in 2003
  3. DTPa vaccine preschool booster immunity rates have remained steady and high
     1. 92% for 3 doses at 12 months of age
     2. 95% at 24 months
     3. 90% for 4 doses at 5 years of age
  4. concern that vaccine induced immunity may be waning and becoming a factor in infection rates
• mortality 0.51% in children < 6 months of age

Assessment

Catarrhal Phase (1-2 weeks, sometimes as short as a few days in infants <3 months)

• General Characteristics:
  • Often indistinguishable from a common cold but highly contagious.
  • Minimal or no fever.
  • Clear nasal discharge that does not become purulent.
  • Mild symptoms like malaise, mild conjunctivitis, pharyngitis, rhinorrhea, sneezing, lacrimation, and mild dry cough.
  • Low-grade fever or afebrile.
• Symptoms:
  • Persistent cough (lasting longer than 2 weeks).
  • Paroxysms of coughing.
  • Inspiratory whoop.
  • Post-tussive vomiting.

Paroxysmal Cough Stage (2-4 weeks with a peak at 2 weeks, may persist up to 10 weeks)

• Infants under age 6 months:
  • Apnea.
  • Cyanosis.
  • Bradycardia.
  • Persistent cough (not in spasms, and whooping is uncommon).
  • Decreased oral intake.
  • Choking or gagging.
  • Gasping.
  • Face reddened.
• Older infants, children, and adults:
  • Gradually progressive cough in spasms to severe coughing fits.
  • Starts as a dry, intermittent cough before progressing to a paroxysmal cough.
  • Coughing spasms result from difficulty clearing thick mucus in the trachea and bronchi.
  • Patients feel as if they cannot breathe during coughing fits.
  • Typically, breathing is unencumbered between coughing fits.
  • Post-tussive emesis may occur.
  • Inspiratory whoop (most common in young children, uncommon under age 6 months, and in teens and adults).
  • High-pitched whooping sound triggered by gasping after a severe coughing spell, occurring when a deep breath is taken against a closed glottis.
• Associated secondary conditions (from severe coughing spells):
  • Subconjunctival hemorrhage.
  • Back pain.
  • Post-tussive emesis.
  • Mallory-Weiss tear.
  • Cyanosis.
  • Cough syncope.
  • Cough fracture (rib fracture).
  • Petechiae (face and trunk).
  • Pneumothorax.
  • Pneumomediastinum.
  • Abdominal or inguinal hernia.
  • Urinary incontinence.
  • Rectal prolapse.

Recovery Phase

• Recovery typically occurs over 2-3 weeks.
• Coughing spasms gradually resolve over 1-3 months.
• Hence, pertussis is often referred to as the “100-day cough” due to its prolonged nature.

Complications

• Infants
  • Hospitalization
  • secondary Pneumococcal otitis media 
  • Apnea (50% of infants)
  • Superimposed Bacterial Pneumonia
    • 20% of infants, with high mortality rate
    • 25% of those < 4 years of age
  • seizures
    • 2% (majority < 2 years of age)
    • related to hypoxia during coughing spasms
  • subconjunctival haemorrhages or facial petechiae 
  • Dehydration
  • intracranial bleeding
  • Encephalopathy
  • bronchiectasis now uncommon
  • Death (rate has been rising for infants)
• Teens and adults
  • Rib Fracture
  • Hernia
  • Prolonged cough (up to 6 weeks)
  • Weight loss (33%)
  • Urinary Incontinence (28%)
  • Syncope (6%)
  • Secondary Bacterial Pneumonia (2-4%)
  • Otitis Media (most common infectious complication)

Investigations

• lymphocytosis prominent
  1. strongly suggestive in an afebrile infant < 3 months of age
• culture of nasopharyngeal aspirate
  1. within 2 weeks onset of cough
  2. difficult to isolate once cough is established
  3. 20% sensitive, 100% specific within first 3 weeks of cough in children
  4. lower sensitivity in older patients
• polymerase chain reaction (PCR)
  1. the investigation of choice
  2. 3 times more sensitive than culture
  3. sensitivity decreases with longer duration of symptoms of most use within 3 weeks of onset of disease
• lower sensitivity in older patients

Management

• O2, suction
• admission required in approximately 25%
  1. required in 2/3 of patients < 6 months of age
• NGT feeding may be necessary
• Antibiotics
  1. Macrolides:: azithromycin/clarithromycin/erythromycin for 14 days may modify the course if given in the catarrhal phase
  2. Azithromycin
     1. adults 500 mg orally then 250 mg daily for 4 days
     2. 6 months 10 mg/kg up to 500 mg then 5 mg/kg up to 250 mg for 4 days
     3. < 6 months 10 mg/kg orally, daily for 5 days
  3. Clarithromycin
     1. adults 500 mg orally twice daily for 7 days
     2. 1 month of age 7.5 mg/kg up to 500 mg
• alternative antibiotic cotrimoxazole if macrolides contraindicated

Prophylaxis

• recommended for
  1. all household contacts of an index case when the household includes
     1. children less than two years who have received less than three doses of vaccine (including newborn infants)
  2. any woman in the last month of pregnancy
  3. all adults and children in a childcare arrangement with an index case
     1. if the group contains children less than two years who have received less than three doses of vaccine
  4. healthcare workers in maternity and neonatal units
  5. infants in maternity and neonatal units where a healthcare worker was the infected case
• should be given as soon as possible
• may be commenced up to 3 weeks after onset of symptoms in the index case
• prophylaxis antibiotics are the same as for treatment

Recommended antibiotic for post-exposure prophylaxis for pertussis – Australian Prescriber – VOLUME 35 : NUMBER 3 : jUNE 2012
Drug	Dose <1 month old	Dose 2–6 months old	Dose >6 months old	Adult dose
Azithromycin	10 mg/kg as a single dose for 5 days	10 mg/kg as a single dose for 5 days	10 mg/kg (max 500 mg) as a single dose for a day, then 5 mg/kg (max 250 mg) as a single dose for 2–5 days	500 mg day 250 mg days 2–5
Clarithromycin	Not recommended	7.5 mg/kg twice daily for 7 days	7.5 mg/kg twice daily (max 500 mg/dose) for 7 days	500 mg twice daily for 7 days
Erythromycin	Use if azithromycin unavailable Age 7–28 days: 10 mg/kg every 8 hours for 7 days	10 mg/kg every 6 hours for 7 days	10 mg/kg (max 250 mg/dose) every 6 hours (max 1 g/day) for 7 days	erythromycin: 250 mg every 6 hours for 7 days erythromycin ethylsuccinate: 400 mg every 6 hours for 7 days
Trimethoprim-sulfamethoxazole	Not recommended	4/20 mg/kg twice daily for 7 days	4/20 mg/kg (max 160/800 mg) twice daily for 7 days	160/800 mg twice daily for 7 days

Isolation

• patients are seldom infectious after cough has been present for > 3 weeks suspected index case should avoid contact with other individuals until at least 5 days of antibiotics have been receive

Vaccination

• Close contacts that are not up to date with their pertussis immunisation should be given DTPa or dTpa as soon after exposure as possible
• Consider dTpa for adults who have not had pertussis-containing vaccine in the last 10 years

School exclusion

• Unimmunised (<3 doses) household and close childcare contacts less than 7 years of age must be excluded from school or child care for 14 days from the last exposure to infection         OR 
• suspected index case should avoid contact with other individuals  until they have taken 5 days of effective antibiotics

When to admit/consult local paediatric team

• Infants less than 6 months of age
• Any child with complications (apnoea, cyanosis, pneumonia, encephalopathy)