Overview
Definition:
Pertussis, commonly known as whooping cough, is a highly contagious bacterial respiratory illness caused by Bordetella pertussis
In infants, it can present with severe, life-threatening complications including apneic spells, which are episodes of cessation of breathing.
Epidemiology:
While vaccination has significantly reduced incidence, pertussis remains a global health concern, with infants under one year of age being the most vulnerable to severe disease and mortality
Outbreaks can occur, particularly in populations with suboptimal vaccination rates
The highest burden of disease is seen in infants less than 2 months old.
Clinical Significance:
Pertussis in infants is a critical medical emergency
Apneic spells are a hallmark of severe disease in this age group and are associated with a significantly higher risk of morbidity and mortality
Prompt diagnosis and appropriate management, including antibiotic therapy, are crucial for improving outcomes.
Clinical Presentation
Symptoms:
Early symptoms resemble a common cold: mild cough, rhinorrhea, and low-grade fever, lasting 1-2 weeks
This is followed by the characteristic catarrhal stage, with paroxysmal coughing fits consisting of 5-10 forceful coughs in rapid succession, often followed by an inspiratory "whoop" (though this may be absent in very young infants)
Vomiting, cyanosis, and fatigue may occur after coughing fits
Apneic spells, characterized by pauses in breathing lasting >10-20 seconds, are a severe manifestation and may be the only sign in neonates and young infants, sometimes presenting as pallor or cyanosis without overt coughing.
Signs:
During paroxysms, infants may become cyanotic and appear distressed
Apneic spells are identified by observing cessation of breathing, often accompanied by bradycardia and hypotonia
Physical examination may reveal poor feeding and weight loss due to the severity of coughing fits and vomiting
Tachypnea and intercostal retractions can indicate secondary pneumonia.
Diagnostic Criteria:
Diagnosis is primarily clinical, supported by laboratory confirmation
Suspected cases in infants with characteristic paroxysmal cough, post-tussive emesis, or whoop are concerning
Laboratory confirmation typically involves PCR testing of nasopharyngeal swabs for B
pertussis DNA, which is highly sensitive and specific during the first 3 weeks of illness
Serology may be used later in the illness or for epidemiological purposes but is less useful for acute diagnosis in infants.
Diagnostic Approach
History Taking:
Detailed history is paramount, focusing on the onset and progression of cough, presence of paroxysms, post-tussive vomiting, and any observed breathing pauses (apnea)
Inquire about exposure to unvaccinated individuals or recent travel
Maternal vaccination status and infant immunization history are crucial
A history of prematurity or underlying respiratory conditions may increase risk.
Physical Examination:
Careful observation of breathing patterns, including episodes of apnea and tachypnea
Assess for signs of respiratory distress such as retractions, nasal flaring, and grunting
Evaluate for cyanosis during or after coughing spells
Assess hydration status and nutritional intake, which can be compromised by frequent vomiting.
Investigations:
Nasopharyngeal swab for Bordetella pertussis PCR is the gold standard for early diagnosis
Culture is less sensitive and takes longer
Complete blood count may show marked lymphocytosis, a characteristic finding
Chest X-ray may be normal or show signs of pneumonia or atelectasis, especially if secondary bacterial infection occurs
Arterial blood gas analysis may be indicated in infants with significant respiratory distress or apneic spells to assess for hypoxia and hypercapnia.
Differential Diagnosis:
In infants, differential diagnoses for severe cough and respiratory distress include bronchiolitis (RSV), pneumonia (bacterial or viral), viral upper respiratory tract infections, choking on foreign bodies, gastroesophageal reflux with aspiration, and congenital airway anomalies
The presence of characteristic paroxysms and post-tussive vomiting helps differentiate pertussis.
Management
Initial Management:
Infants with severe pertussis, particularly those experiencing apneic spells, require hospitalization, often in an intensive care setting
Supportive care is critical
This includes close cardiorespiratory monitoring, pulse oximetry, and suctioning of secretions to clear the airway
Oxygen therapy is provided as needed.
Medical Management:
Antibiotic therapy is indicated to reduce the duration of infectiousness and may lessen the severity and duration of illness, although its effect on established paroxysms and apnea is debated
Macrolides are the preferred agents
For infants: Azithromycin is often preferred due to its favorable dosing schedule and good penetration
Typical dose: 10 mg/kg orally twice daily for the first day, then 5 mg/kg orally once daily for 4 days (total 5-day course)
Erythromycin (50 mg/kg/day divided into 3 doses for 14 days) or Clarithromycin (15 mg/kg/day divided into 2 doses for 7 days) are alternatives
Post-exposure prophylaxis with macrolides is recommended for close contacts, especially unvaccinated infants and pregnant women.
Supportive Care:
Management of apneic spells often involves careful stimulation (e.g., tactile stimulation) and, if ineffective, bag-mask ventilation and intubation with mechanical ventilation for severe, persistent apnea
Nutritional support may be required via nasogastric or orogastric tube if oral intake is compromised
Strict isolation precautions should be maintained until 5 days of appropriate antibiotic therapy are completed
Close monitoring for complications such as pneumonia and encephalopathy is essential.
Prognosis:
The prognosis for pertussis in infants depends heavily on age at onset and the presence of complications, particularly apnea
Infants with apneic spells have a significantly higher risk of mortality and long-term neurological sequelae
Early diagnosis, aggressive supportive care, and prompt antibiotic treatment improve outcomes, but severe cases can still be fatal despite optimal management
Survivors of severe pertussis may experience prolonged recovery.
Complications
Early Complications:
Apneic spells leading to hypoxia and potential brain injury
Secondary bacterial pneumonia is common
Otitis media
Vomiting leading to dehydration and malnutrition
Esophageal tears from forceful vomiting
Hemorrhagic phenomena (petechiae, ecchymoses, epistaxis, conjunctival hemorrhage) due to increased intrathoracic pressure.
Late Complications:
Neurological sequelae from hypoxic brain injury, including seizures and developmental delay
Persistent cough and reactive airway disease
Weight loss and failure to thrive.
Prevention Strategies:
The most effective strategy is vaccination
Ensuring high rates of maternal pertussis vaccination during pregnancy and infant immunization according to national schedules significantly reduces the risk of severe disease and mortality in infants
Prompt identification and treatment of infected individuals to reduce transmission
Prophylactic antibiotics for close contacts.
Key Points
Exam Focus:
Pertussis in infants is defined by paroxysmal cough, post-tussive emesis, and often *apneic spells*, not necessarily a "whoop"
Macrolides (Azithromycin preferred) are first-line therapy
Apnea in infants is a medical emergency requiring intensive supportive care and monitoring.
Clinical Pearls:
Always consider pertussis in any infant presenting with severe cough and respiratory compromise, especially if unvaccinated or incompletely vaccinated
Apneic spells in neonates may be the sole manifestation
Even after antibiotics, cough can persist for weeks
Meticulous airway suctioning and monitoring are crucial for infants with apnea.
Common Mistakes:
Underestimating the severity of pertussis in infants, leading to delayed hospitalization
Misattributing apneic spells to other causes without considering pertussis
Inadequate supportive care for infants with apnea, focusing solely on antibiotics
Delaying post-exposure prophylaxis for close contacts, including pregnant women.