33-10: Bordetella Pertussis Infection (Whooping Cough)

Pertussis is an acute infection of the respiratory tract caused by B pertussis that is transmitted by respiratory droplets. The incubation period is 7–17 days. Half of all cases occur before age 2 years. Neither immunization nor disease confers lasting immunity to pertussis. Consequently, adults are an important reservoir of the disease.

The symptoms of classic pertussis last about 6 weeks and are divided into three consecutive stages. The catarrhal stage is characterized by its insidious onset, with lacrimation, sneezing, and coryza, anorexia and malaise, and a hacking night cough that becomes diurnal. The paroxysmal stage is characterized by bursts of rapid, consecutive coughs followed by a deep, high-pitched inspiration (whoop). The convalescent stage begins 4 weeks after onset of the illness with a decrease in the frequency and severity of paroxysms of cough. The diagnosis often is not considered in adults, who may not have a typical presentation. Cough persisting more than 2 weeks is suggestive. Infection may also be asymptomatic.

The white blood cell count is usually 15,000–20,000/mcL (rarely, as high as 50,000/mcL or more), 60–80% of which are lymphocytes. The diagnosis is established by isolating the organism from nasopharyngeal culture. A special medium (eg, Bordet-Gengou agar) must be requested. Polymerase chain reaction assays for B pertussis may be available in some clinical or health department laboratories.

Acellular pertussis vaccine is recommended for all infants, combined with diphtheria and tetanus toxoids (DTaP). Infants and susceptible adults with significant exposure should receive prophylaxis with an oral macrolide. In recognition of their importance as a reservoir of disease, vaccination of adolescents and adults against pertussis is recommended (see Table 30–7 and www.cdc.gov/vaccines/schedules). Two tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine (Tdap) products (BOOSTRIX, GlaxoSmithKline and ADACEL, Sanofi Pasteur) are licensed by the FDA. Adolescents aged 11–18 years (preferably between 11 and 12 years of age) who have completed the DTP or DTaP vaccination series should receive a single dose of either Tdap product instead of Td (tetanus and diphtheria toxoids vaccine) for booster immunization against tetanus, diphtheria, and pertussis. Adults of all ages (including those older than age 64 years) should receive a single dose of Tdap. In addition, pregnant women should receive a dose of Tdap during each pregnancy regardless of prior vaccination history, ideally between 27 and 36 weeks of gestation, in order to maximize the antibody response of the woman and the passive antibody transfer to the infant. For any woman who was not previously vaccinated with Tdap and for whom the vaccine was not given during her pregnancy, Tdap should be administered immediately postpartum. The CDC has eliminated the recommendation that a 2-year period window is needed between receiving the Td and Tdap vaccines based on data showing that there is not an increased risk of adverse events.

Antibiotic treatment should be initiated in all suspected cases. Treatment options include erythromycin, 500 mg four times a day orally for 7 days; azithromycin, 500 mg orally on day 1 and 250 mg for 4 more days; or clarithromycin, 500 mg orally twice daily for 7 days. Trimethoprim-sulfamethoxazole, 160–800 mg orally twice a day for 7 days, also is effective. Treatment shortens the duration of carriage and may diminish the severity of coughing paroxysms. These same regimens are indicated for prophylaxis of contacts to an active case of pertussis who are exposed within 3 weeks of the onset of cough in the index case.