Pertussis

Background

• “Whooping cough”. The “whoop” is caused on inspiration between coughs.
• Most common in kids < 1yo, because they haven’t completed the whole vaccine series, AND adults, who have waning immunity.
• One of the only vaccine preventable diseases that has increased in prevalence recently
• Up to 20% of adults with cough >2 weeks have serologic evidence of pertussis
• Bordetella pertussis, a gram-negative coccobacillus

Pathophysiology

• Transmitted by aerosolized droplets, extremely contagious
• Infects ciliated respiratory cells (rarely goes hematogenous), creates toxins damaging respiratory epithelium.

Clinical Features

A young boy coughing due to pertussis.

• Incubation period several days-3 weeks
• 3 stages:
  • Catarrhal phase: lasts 1-2 wks. Clinically indistinguishable from other URIs; dry cough starts near the end. Greatest infectivity phase.
  • Paroxysmal phase: lasts 2-4 weeks => fever improves, cough worsens. Staccato cough + whoop (present in 1/3 kids), post-tussive emesis (often in adolescents, adults). Infants can present as apnea. Patients often appear well between coughing episodes.
    • Petechiae, epistaxis, pneumothorax, and/or subconjunctival hemorrhage may occur due to high intrathoracic pressures during coughing.
  • Convalescent phase: lasts weeks-months; residual cough

Sequelae

• Pneumonia superinfections
• Rib fracture
• Pneumothorax
• Aspiration of gastric contents
• CNS complications
• Mucous plugs, obstructed airway
• Secondary bacterial infection
• Increased intrathoracic pressures
  • Rectal prolapse
  • Ruptured diaphragm
  • Hernia

Differential Diagnosis

Pediatric fever

• Upper respiratory infection (URI)
• UTI
• Sepsis
• Meningitis
• Febrile seizure
• Pneumonia
• Acute otitis media
• Whooping cough
• Unclear source
• Kawasaki disease
• Neonatal HSV

Evaluation

• WBC elevated in infants (20-100) with large amount of lymphs (85%), adults and infants < 6 mo may be WNL
• CXR with peribronchial thickening, atelectasis, and/or consolidation
• Nasopharyngeal swab can identify it in 3-7 days; often neg in adults.
• Cough for >2 weeks, post tussive emesis, feeling well otherwise, treat them empirically. Especially if infant or pregnant people at home.

Management

Acute Disease

• Supportive
  • Suction in infants, hydration. Neonates with apnea should be admitted to the ICU.

Antibiotics

• Antibiotics do not help with severity or duration but may decrease infectivity.
• A reasonable guideline is to treat persons aged >1 year within 3 weeks of cough onset and infants aged <1 year and pregnant women (especially near term) within 6 weeks of cough onset.
• TMP--SMZ should not be administered to pregnant women, nursing mothers, or infants aged <2 months.
• The following regemins are for active disease or postexposure prophylaxis. If a patient is has confirmed disease and is likely to be in contact with infants or pregnant women then the patient should be treated as up to 6-8 weeks after the onset of their illness.

< 1 month old

Same antibiotics for active disease and postexposure prophylaxis

• Azithromycin 10mg/kg (max 500mg/day) daily x 5 days

>1 month old

• Azithromycin 10mg/kg (max 500mg/day) daily x 5 days
  • if > 6 months old then day 2-5 of treatment should be reduced to 5mg/kg (250mg/day max)
• TMP/SMX 4mg/kg PO BID daily for 14 days (if > 2 months old)

Adults

andy of the following antibiotics are acceptable although azithromycin is most commonly prescribed

• Azithromycin 500mg PO once daily for day #1 then 250mg PO once daily for days #2-5
• Clarithromycin 500mg BID x7 days
• Erythromycin 500mg QID x7 days

Isolation

• Droplet

Post-Exposure Prophylaxis

• Prophylaxis for all household exposures of known Pertussis
• High risk people exposed to pertussis: infants, women in 3rd trimester of pregnancy, immunocompromised, severe asthma, people with close contact to infants <1year, people who work in neonatal ICUs / maternity wards.
• Patients are considered infectious for 3 wks after start of paroxysmal phase, or after 5 days of antibiotics

Prevention

• Vaccinate women during each pregnancy preferably between 27-36 wks, regardless of previous Tdap admin
• Immunity wanes 8 y after immunization. Often elderly will get the disease and transmit it to young unimmunized infants.

Tetanus Vaccine Selection Guide

Age	If No Pertussis Contraindications	If Pertussis Contraindicated	Comments
2mo - 7yrs	DTaP	DT	DT available from pharmacy
7yrs - 10yrs	Td	Td
10yrs	Tdap(Adacel)^	Td	^Off label use, but appears safe and immunogenic
11yrs - 16yrs	Tdap(Adacel)	Td
16yrs - 65	Tdap(Adacel)^^	Td	^^Use Td if patient is known to have received prior Tdap
65yrs +	Td	Td	Consider TIG for tetanus prone wound plus Td(tetanus immune globulin)

Caveats

• Adolescents who have already gotten a booster dose of Td are encouraged to get a dose of Tdap as well. Waiting 5 years after their last Td is encouraged but not required. A period of at least 2 years between Td and Tdap is recommended in these cases.
• Pregnancy is not a contraindication to Tdap.
• Stable neurologic disorders and family history of vaccine reactions are not contraindications to receiving these vaccines.
• No vaccine has ever been shown to play any role in the development of autism or autism spectrum disorders.

See Also

• Tdap
• Vaccination schedule

References

Authors

Ross Donaldson