Pertussis - crying baby

Pertussis

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Winston, a 4 month old boy, presents to your emergency department after his mother noticed, during his last feed, that he appeared to stop breathing for around 15 seconds and turned blue.

He restarted breathing spontaneously. Further history reveals a two day history of feeding difficulties, cough, irritability and rhinorrhoea. He has also had a low grade temperature (37.8 0C). There has been no diarrhoea and a few vomits, but only after coughing. He has no rashes. His oral intake has been reduced to about half normal, for the last 24 hours.

Bottom Line

  • Have a low threshold for suspicion in any child with a prolonged cough, especially those incompletely immunised
  • Pertussis has a non-typical presentation in infants
  • In clinically or lab diagnosed pertussis, antibiotics do not reduce the severity or frequency of coughing paroxysms. Antibiotics do render the child noninfectious
  • Due to the high risk of morbidity and mortality in infants less than six months of age who are incompletely immunised, contact prophylaxis is recommended for families who have an infant less than six months of age

 

Further Assessment

Birth History

Winston was born at term weighing 3700g. Apgars were 91, 95 after an SVD without any risk factors for sepsis. His well neonate check and six week GP reviews were unremarkable. He is exclusively breastfed. He is up to date with his immunisations.

Family History

Of note, Winston’s 11 year old brother has had two weeks of rhinorrhoea and cough, but is clinically well.

Examination

You see a slightly tachypnoeic, thriving 4/12 male. Chest clear. Mildly dehydrated. Irritable.

Normotensive fontanelle. No rashes. No focal findings on chest. Unremarkable cardiovascular & abdominal examinations. ENT; TMs are mild erythematous bilateral without effusion, tonsils are also mildly erythematous, not overly enlarged.

What is the most concerning feature of this history?

Apnoea – apnea is a particularly concerning feature in infants.

What are your differentials and most likely diagnosis - why?

Whooping cough, caused by bordetella pertussis, a gram negative coccobacillus whose only reservoir is humans. It’s transmitted by respiratory secretions, particularly in the first few weeks after exposure.

Clinically, pertussis classically progresses in three stages.

  • Firstly, the catharrhal phase which consists of one to two weeks of nonspecific symptoms.
  • This is followed by the paroxysmal phase, in which the characteristic ‘whoop’ sound at the end of a coughing paroxysm may be heard (infants and older children are less likely to have the typical whooping cough).
  • Finally comes the convalescent phase in which the coughing paroxysms become less frequent and less severe.

Noteably, infants may manifest pertussis infection only as feeding difficulties, cough or apnoeas. Also, immunised children may manifest a more attenuated illness that doesn’t demonstrate the classic three phases of illness.

How is it diagnosed?

Laboratory diagnosis is by nasal swab or nasopharyngeal aspirate showing PCR positive for bordetella pertussis.

Additionally, when considering which children to swab, there was a distinct paucity of evidence. There were several comparisons of PCR vs culture, but no firm criteria about who should score an NPA or flocked swab in the first place.

The US CDC recommends: “Early diagnosis and treatment might limit disease spread. When pertussis is strongly suspected, attempts to identify and provide prophylaxis to close contacts should proceed without waiting for laboratory confirmation. When suspicion of pertussis is low, the investigation can be delayed until there is laboratory confirmation of the diagnosis. However, prophylaxis of infants and their household contacts should not be delayed because pertussis can be severe and life-threatening to young infants.”

Ditte & colleagues’ excellent (but quite technical) 2004 article investigated a sample size of 3096 patients, swabbed for suspected pertussis.

 

(From 3096 pts) PCR Culture
Sensitivity 97% 58%
Specificity 93% in culture positive samples.

 

PCR was superior for detection in patients aged 6m-3y, and was highly sensitive for diagnosis of pertussis.

Also of note, pertussis serology may be of use to confirm diagnosis around the time a patient enters the catharral phase, but will unlikely change management as discussed above.

Who is at most risk?

Infants under six months have the highest mortality from pertussis; the mortality rate is estimated around 1%, with 80% of these deaths occurring in infants under 2 months. Comorbid apnoea, pneumonia and seizures may complicate pertussis infection. Less commonly, a leukocytosis >50,000x10x9/L or encephalopathy potentially caused by pertussis toxin may occur and is associated with a poor prognosis.

 

Treatment

Let’s have a look at the evidence around antibiotic management of whooping cough as well as the indications for prophylaxis. This Cochrane Review (assessed as up to date in Jan 2011) is the basis for a number of current guidelines.

Altunaiji SM, Kukuruzovic RH, Curtis NC, Massie J. Antibiotics for whooping cough (pertussis). Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD004404. DOI: 10.1002/14651858.CD004404.pub3.

The review looks at 13 RCTs regarding the efficacy of antibiotics for treatment & prophylaxis of pertussis. Eleven trials looked at treatment and had the following objectives:

Do antibiotics achieve microbiological eradication of B. pertussis?

  • Multiple studies showed a number of agents successfully eradicating b. pertussis, including erythromycin, oxytetracycline.
  • Azithromycin & clarithromycin as macrolides equivalent to erythromycin have been shown effective at eradicating b. Pertussis.
  • A number of head to head studies showed no superior agent. However, a 1997 study showed roxithromycin was two to four-fold less effective at b. pertussis eradication vs erythromycin.

Do antibiotics improve the clinical illness of whooping cough?

  • No difference in mortality.
  • With regard to clinical cure/ remission; erythromycin ethyl succinate (EES) vs erythromycin estolate. Patients judged they were equivocal re: frequency of cough, and that erythromycin estolate was slightly superior to EES, regarding clinical cure / remission.
  • Erythromycin & azithromycin had no relapses after proven negative culture post-treatment.

What is the appropriate dose and duration of therapy?

  • There was no benefit for a prolonged course of antibiotics vs a standard course.

What are the side effects profile of antibiotics used to treat whooping cough?

  • Regarding side effects, azithromycin 3/7 was superior to erythromycin ethyl succinate 14/7 and clarithromycin 7/7 was superior to erythromycin estolate 14/7
  • Compliance was best for azithromycin vs erythromycin estolate and clarithromycin vs EES

Additionally, Honien et al (1999) describe seven cases of infantile hypertrophic pyloric stenosis in a cohort of 200 neonates treated with erythromycin; a significantly increased risk or IHPS in this population.

 

Prophylaxis

Two trials (401 patients in total) reviewed prophylaxis:

Do antibiotics prevent the clinical illness of whooping cough?

  • “slightly less” but not statistically significant frequency of whooping cough, paroxysms in household contacts of the prophylaxis arm.
  • “slightly lower” but not statistically significantly lowered attack rate in prophylaxis groups.

The side effects profile of antibiotics used for prophylaxis of whooping cough?

  • Placebo was better than erythromycin estolate for compliance & side effect profile.

Of note, erythromycin estolate is not available in Australia.

The reviewers commented on the marked heterogeneity of studies with regard to the outcome measures & definitions. They note that treatment renders patients noninfectious but does not alter the clinical course. Consequently, they make the following recommendations.

The best regimens for microbiological clearance, with fewer side effects, are:

  • three days of azithromycin (10 mg/kg as a single dose);
  • five days of azithromycin (10 mg/kg on the first day of treatment and 5 mg/kg once daily on the second day to fifth days of treatment); or
  • seven days of clarithromycin (7.5 mg/kg/dose twice daily).

Seven days of trimethoprim/sulphamethoxazole (20 mg trimethoprim with 100 mg sulphamethoxazole per dose, twice daily, for children under six months of age; double this dose for older children) appears to be effective in eradicating B. pertussis from the nasopharynx and may serve as an alternative antibiotic treatment for patients who can not tolerate a macrolide.

Additionally, in Australia, a pertussis booster vaccine is recommended for close household contacts of newborns; this advice is part of a neonatal discharge check within hospital.

 

Antibiotics for prophylaxis against whooping cough – summary

There is insufficient evidence to determine the benefit of prophylactic treatment of pertussis contacts. Prophylaxis with antibiotics was significantly associated with side effects and did not significantly improve clinical symptoms, whoop, paroxysmal cough, number of cases who develop culture-positive B. pertussis or paroxysmal cough for more than two weeks in contacts older than six months of age. Due to the high risk of morbidity and mortality in infants less than six months of age who are incompletely immunised, contact prophylaxis is recommended for families who have an infant less than six months of age. The recommended antibiotics and dosages for contact prophylaxis are the same as those recommended in the treatment of whooping cough.

 

Additionally, the American CDC guidelines written in 2006 were reviewed more recently and not rewritten. They were published prior to the 2007 Cochrane Review.

 

 

References

Altunaiji SM, Kukuruzovic RH, Curtis NC, Massie J. Antibiotics for whooping cough (pertussis). Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD004404. DOI: 10.1002/14651858.CD004404.pub3.

Chan MH et al. The California Pertussis Epidemic 2010: A Review of 986 Pediatric Case Reports From San Diego County J Ped Infect Dis (2012) 1 (1): 47-54 doi:10.1093/jpids/pis007 Accessed 24/06/2013.

Ditte MD, Dohn B, Madsen J, Jensen JS, Comparison of culture and PCR for detection of Bordetella pertussis and Bordetella parapertussis under routine laboratory conditions. J Med Microbiol August 2004 vol. 53 no. 8 749-754.

Faulkner A, Skoff T, Martin S, Cassiday P, Lucia Tondella M, Liang J, Ejigiri OG, Surveillance Manual, 5th Edition, 2011 Pertussis: Chapter 10-1. 8 July 2011. Accessed 09/07/2013.

Snyder, J & Fisher, Pertussis in Childhood. Pediatrics in Review Vol. 33 No. 9 September 1, 2012 pp. 412 -421 (doi: 10.1542/pir.33-9-412).

 

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About 

A Paediatric Trainee based in Queensland, Australia, Henry is passionate about Adolescent Medicine & General Paediatrics, with a strong interest in Medical Education & Clinical Teaching. An admitted nerd & ironman with a penchant for Rubik's Cubes & 'Dad jokes'.

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