Bordetella Pertussis and Bordetella Parapertussis Infections

Abstract & Commentary

Synopsis: In a highly immunized population, Bordetella pertussis and Bordetella parapertussis infections were detected by culture and PCR in 26.2% of patients with paroxysmal cough, with 32% of these caused by B. parapertussis. B. parapertussis infections were as common as B. pertussis in children before school entry. B. pertussis infections were more common in school-age children and adults.

Source: He Q, et al. Whooping cough caused by Bordetella pertussis and Bordetella parapertussis in an immunized population. JAMA 1998;280:635-637.

A prospective study of 584 patients (median age, 9 years; range, 7 days to 74 years) with paroxysmal cough, characterized as bouts of uncontrollable coughing of any duration, was conducted in Finland from October 1994 through March 1997. A total of 153 (26.2%) patients had Bordetella infection by either culture or polymerase chain reaction (PCR): 93 (60.8%) had B. pertussis, 49 (32.0%) had B. parapertussis, and 11 (7.2%) had both. There was no difference in the frequency of symptoms (e.g., whooping, vomiting, mean duration of cough) between B. pertussis and B. parapertussis infections. Of 198 patients with paroxysmal cough for less than 7 days, 35 (17.7%) had B. pertussis and 24 (12.1%) had B. parapertussis. Of 366 patients with paroxysmal cough for more than seven days, 66 (18.0%) had B. pertussis and 32 (8.7%) had B. parapertussis. The annual incidence rates of B. pertussis and B. parapertussis infections were 16.6 and 9.5 in children younger than 2 years of age, 19.6 and 20.5 in children 2-6 years, 27.2 and 15.1 in children 7-15 years (P = 0.005), and 1.5 and 0.2 in persons 16 years of age (P < 0.001).

Comment by Hal B. Jenson, MD, FAAP

This prospective study in a highly immunized population (with coverage rates of DTP vaccine of 98%) showed that Bordetella infections, and especially B. parapertussis infections, were more common than previously thought. Infections with B. parapertussis were as common as B. pertussis in preschool children. B. pertussis and B. parapertussis infections occurred with similar frequency through 6 years of age, but B. pertussis infections were more frequent in school-age and older children and adults, suggesting that immunity following pertussis (DTP) vaccination decreases over time.

B. pertussis and B. parapertussis cause similar symptoms, as also shown in this study, although the disease caused by B. parapertussis is asymptomatic or usually milder than that caused by B. parapertussis. Patients with either infection are usually not suspected of having Bordetella infection, and the appropriate tests (cultures) are not obtained. It appears from this and other studies that the whole-cell B. pertussis vaccine (DTP, or DTwP) does offer some partial protection against B. parapertussis infection. As we move to generalized use of the acellular pertussis vaccine (DTaP), it is likely that we will see an increased incidence of the milder disease caused by B. parapertussis. It is uncertain, however, if, as clinicians, we will be able to clinically distinguish the mild symptoms of B. parapertussis infection from other causes of cough. Recognizing Bordetella infections may be important in preventing spread and secondary cases by treating the index case and close contacts, although antibiotic treatment has no significant effect on the acute illness.

It is also possible that booster immunizations against pertussis, which historically have not been given to persons 7 years of age due to the high rate of adverse events of the whole-cell DTP vaccine, may be incorporated into the DT booster immunizations that are currently recommended for adults every 10 years throughout life. The four DTaP vaccines, currently licensed only for children younger than 7 years of age, are composed of different numbers of B. pertussis components (Acel-Imune, 4; Certiva, 1; Infanrix, 3; Tripedia, 2). The newest DTaP vaccine, Certiva, contains only inactivated pertussis toxin, which is not present in B. parapertussis and would be unlikely to produce cross-reacting antibodies. Although all four DTaP vaccines are efficacious in preventing pertussis in childhood and no preference is indicated by either the AAP or CDC, it is possible that the protection against B. parapertussis infections may become a consideration in the future DTaP recommendations, especially if acellular pertussis is eventually included with DT vaccinations in adults.