RS08 - Pertussis

What is the causative agent of whooping cough?

Bordetella pertussis.

What are the basic characteristics of Bordetella pertussis?

Gram-negative coccobacillus; non-motile; obligate aerobe; dies quickly outside of the host.

What disease does Bordetella pertussis cause?

Whooping cough (pertussis).

How is pertussis transmitted?

Person-to-person via respiratory droplets.

How contagious is pertussis?

Very contagious; >90% of non-immunized children become infected if exposed.

What is the incubation period for pertussis?

Less than 1 week to greater than 3 weeks.

What are the three clinical phases of pertussis?

Catarrhal phase, paroxysmal phase, and convalescent phase.

What occurs during the catarrhal phase of pertussis?

Cold-like symptoms lasting 1–2 weeks; patient is highly infectious.

During which phase is a patient most infectious?

Catarrhal phase.

What occurs during the paroxysmal phase of pertussis?

Violent repetitive coughing lasting 1–6 weeks; whooping inhalation; vomiting.

What causes the “whooping” sound in pertussis?

Forceful inhalation after a coughing spasm.

What occurs during the convalescent phase of pertussis?

Recovery phase lasting 7–10 days; coughing severity decreases; patient is no longer contagious; chance for secondary infection.

During which phase is a patient considered no longer infectious?

Convalescent phase.

Why does pertussis cause violent coughing that lasts a long time?

Loss of ciliated epithelial cells prevents normal mucus clearance, leaving coughing as the only mechanism of clearance.

What are the three major virulence factors produced by Bordetella pertussis?

Pertussis toxin (Ptx), filamentous hemagglutinin (Fha), and tracheal cytotoxin.

What type of toxin is pertussis toxin (Ptx)?

An A-B toxin.

How does pertussis toxin affect host cells?

Inactivates cellular G proteins, disrupts cell signaling, and increases cAMP levels.

What are the effects of increased cAMP caused by pertussis toxin?

Increased mucus production, impaired cilia, and reduced phagocytosis.

What is filamentous hemagglutinin (Fha)?

A surface adhesin.

What is the role of filamentous hemagglutinin in infection?

Attachment to ciliated host cells of the nasopharynx, trachea, bronchi, and bronchioles.

What is tracheal cytotoxin?

A toxin that causes release of nitric oxide from goblet cells.

What are the effects of tracheal cytotoxin on the respiratory tract?

Triggers inflammation and causes death of ciliated epithelial cells.

What are classic symptoms of whooping cough?

Paroxysmal coughing, whooping inhalation, and post-tussive vomiting.

Which population is at greatest risk for severe pertussis?

Babies younger than 1 year old.

What severe symptoms may infants experience with pertussis?

Apneic episodes, difficulty breathing, and cyanosis.

What are common complications of pertussis?

Pneumonia (leading cause of death), otitis media, convulsions, and secondary bacterial infections.

What ocular findings can be associated with pertussis?

Subconjunctival hemorrhage and eyelid ecchymosis (black eye) caused by coughing paroxysms.

How is pertussis treated?

Antibiotics such as erythromycin and azithromycin.

When are antibiotics ineffective in pertussis?

Once the patient is in the paroxysmal stage.

Is there a vaccine to prevent pertussis?

Yes.

What type of pertussis vaccine is used?

Acellular pertussis (inactivated) vaccine.

Can the acellular pertussis vaccine cause pertussis?

No.

What components may be included in the acellular pertussis vaccine?

Inactivated pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (Pn), and fimbriae/pili.

What is the DTaP vaccination schedule?

2 months, 4 months, 6 months, 18 months, and 4–6 years.

What vaccine is recommended to address waning immunity?

Tdap.

When is Tdap first administered?

One dose at 11–12 years old.

How often are Tdap boosters recommended?

Every 10 years.

How long does protective immunity from pertussis vaccination last?

Approximately 5–10 years.

Why is herd immunity important for pertussis?

Protects infants who are not fully immunized until 2 months of age.

Who should receive pertussis boosters to support herd immunity?

Parents, grandparents, caregivers, and anyone in contact with infants.

When does the CDC recommend Tdap vaccination during pregnancy?

During the early part of the third trimester of every pregnancy.

Why is Tdap recommended during pregnancy?

Maternal antibodies transfer to the baby, providing early protection.

How does maternal vaccination help prevent infant pertussis?

Protects the mother and prevents transmission to the infant.

What virulence factor inactivates cellular G proteins and increases cAMP?

Pertussis toxin.

What virulence factor is responsible for adhesion to respiratory epithelial cells?

Filamentous hemagglutinin.

What virulence factor causes inflammation and death of ciliated epithelial cells?

Tracheal cytotoxin.

Why are booster vaccines necessary for pertussis?

Immunity wanes after 5–10 years, increasing susceptibility and risk to infants and pregnant women.