Pertussis – AFP 2006

• Bordetella pertussis, a highly communicable gram-negative coccobacillus, causes pertussis (whooping cough).
• B. pertussis is an exclusively human pathogen that is transmitted via airborne droplets and highly contagious.
• The incubation period is typically approximately one week but may be three weeks or longer.

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The clinical dx definition

• a cough illness lasting two weeks without clear cause and one of the following symptoms:
  • paroxysms of coughing,
  • inspiratory whoop, or
  • posttussive emesis,
  • apnea (infant <1yr)
• In the setting of an outbreak or known close contact to a confirmed case of pertussis, the presence of a cough lasting ≥2 weeks is sufficient for clinical diagnosis (even in the absence of other symptoms).

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Confirmed dx definition

1. Patient’s illness meets criteria for “clinical case” plus one of the following: positive PCR assay, epidemiologic linkage to a laboratory- confirmed (PCR assay or culture) case or
2. Acute cough illness of any duration and positive Bordetella pertussis culture

Probable dx definition

Patient’s illness meets criteria for “clinical case” plus all of the following: negative PCR assay, negative B. pertussis culture, no epidemiologic linkage to a laboratory-confirmed (PCR assay or culture) case

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Ix:

• Patients with suspected early pertussis should be tested with nasopharyngeal culture and PCR.
• For patients with more than four weeks of cough, only serology is useful but the lack of a widely available, standardized test limits its use

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Tx:

• Antihistamines, steroids, beta agonists, and immunoglobulins are not routinely recommended for pertussis treatment.
• Azithromycin (Zithromax) and clarithromycin (Biaxin) are recommended therapies for eradicating B. pertussis that are as effective as erythromycin but with better adherence to therapy.

Clarithromycin (Biaxin)

15 mg per kg divided into two doses per day for seven days (maximum dosage: 1 g per day)

B. pertussis eradication rate similar to that of a 14-day erythromycin regimen with fewer side effects and better adherence; not FDA approved for pertussis

Prevention:

• Close household contacts of patients with pertussis should be treated with antibiotics to prevent disease.
• Adolescents should receive Tdap vaccination instead of a Td booster to reduce the incidence of pertussis.
• Adults should receive a one-time Tdap booster instead of a Td booster to reduce the incidence of pertussis.

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Pertussis infection in individuals w/o immunity (no prev vaccine) is characterized by 3 phases:

The total duration of all three phases is typically about three months.

Catarrhal	1-2 week	xs Lacrimation, low-grade fever, malaise, mild conjunctival inflammation/injection, rhinorrhea, late-phase nonproductive cough Dx test more accurate during this phase	Insidious onset Gradually worsening symptoms
Paroxysmal	1-6 week	Paroxysms (bursts of vigorous coughing during a single exhalation) followed by an inspiratory “whooping” sound, post-tussive cyanosis, and emesis – pt often feel well between cough paroxysms – triggered by respiratory irritants (steam, mist, laughing, stretching yawning, exercise) & worse at night	Peaks after two weeks Weight loss, leukocytosis, and lymphocytosis are common
		In infants younger than six months (especially those younger than four weeks): apnea, bradycardia, prolonged cough, poor feeding, no paroxysms
Convalescent	2-12 week	Paroxysms gradually improve but recur with respiratory infections usually last 1-2 weeks	White blood cell count normalizes

In adolescents or adults with history of prior infection or vaccine-induced immunity, classic manifestations often do not occur. The only symptom may be prolonged cough.

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References:

• http://www.aafp.org/afp/2006/0801/p420.html
• UpToDate Jan 2015