Pertussis

PEDIATRIC INFECTIOUS DISEASE NEWSLETTER
Volume 14, Number 1, January/February, 1999

Topic of the Month: Pertussis
Around the Region

Pertussis, or whooping cough, is an acute infection of the respiratory tract caused by the bacterium Bordetella pertussis. It is characterized in most patients by a paroxysmal cough followed by a characteristic inspiratory whoop. Complications of pertussis include secondary bacterial pneumonia, neurological complications such as seizures and encephalopathy and other conditions resulting from the pressure effects of coughing such as pneumothorax. Incidence and complications are highest among those less than one year of age.

In the first part of this century, pertussis was one of the most common diseases of childhood affecting approximately 150/100,000 between 1922 and 1940. In fact, between 1926-1930 there were over 36,000 deaths from pertussis, mainly in children < 1 year. Between 1980 and 1991 there was an average of 1.2 cases per 100,000(1). However, since the 1980's, the incidence of pertussis has steadily increased with surveillance numbers from 1997 23% higher than 1995. These data, reported at the 1998 ICAAC conference by Dr. Kris Bisgard and colleagues from the CDC also show that 46% of pertussis cases were reported in people over 10 years of age while 43% were in children younger than 5(2). It has been reported that up to 25% of adults who see doctors for a persistent cough have pertussis(3). While not a serious disease in adolescents and adults, these groups can transmit the disease to unprotected infants and children.

Although indirect spread may occur, transmission is primarily airborne via respiratory secretions. Once infection is initiated in the respiratory tract of susceptible persons, via attachment of organisms, immune cell function is inhibited allowing infection to continue and local tissue damage to occur. Although systemic illness is rare, leukocytosis with lymphocytosis does occur.

The clinical manifestations vary according to the age of the patient. The incubation period is between 6 and 20 days(4). The illness is divided into 3 stages; catarrhal, paroxysmal and convalescent, lasting at least 6-8 weeks ("pertussis" means 100 day cough).

The catarrhal stage occurs first with patients presenting with rhinorrhea, mild cough and conjunctival injection. The patient may be febrile. This is followed by the paroxysmal stage which may last up to 4 weeks. This stage is characterized by a repetitive series of coughs followed by a sudden massive inspiratory effort producing a characteristic whoop in children with small airways. (Adults do not usually whoop). Several episodes may occur sequentially followed by post-tussive vomiting. Between attacks the patient may seem fine. Attacks may be triggered by any stimulus, or even by suggestion(4).

In the convalescent stage, lasting 1-2 weeks, episodes decrease in frequency and severity. Cough, however, may persist for several months. Several studies have indicated B. pertussis to be the agent responsible for persistent cough in adults despite immunization status(3).

Infants may present with apnea only. Complications of pertussis can be life threatening. Pneumonia, usually secondary bacterial pneumonia, is responsible for >90% of deaths in children less than 3 years of age. Otitis media is common. Convulsions and coma related to anoxia can occur.

Differential diagnosis includes other respiratory viruses including adenovirus, parainfluenza viruses, respiratory syncytial virus as well as mycoplasma. Bordetella parapertussis also causes a similar pertussis-like illness and can only be confirmed by culture or PCR.

Diagnosis may be made clinically using the CDC or WHO clinical case definition of pertussis ("a cough illness lasting at least 2 weeks with one of the following: paroxysmal cough, inspiratory whoop or post-tussive vomiting without apparent cause as reported by a health professional) or by laboratory methods including isolation of B. pertussis from a clinical specimen or a positive PCR (polymerase chain reaction) assay. According to the CDC, a clinical case definition is appropriate for endemic or sporadic cases. Direct florescent antibody (DFA) has low sensitivity and variable specificity, therefore, should not be relied upon as laboratory documentation. Lymphocytosis frequently occurs with absolute lymphocyte counts as high as 20,000/mm3. However, there may be no lymphocytosis in very young infants, vaccinated children or with mild disease in adults.

Although drug therapy does not shorten disease, it will eliminate nasopharyngeal carriage and thus reduce the likelihood of transmission to susceptibles. Recognized exposed individuals should receive prophylactic treatment regardless of age or immunization status. Erythromycin and trimethoprim/sulfamethoxazole have both been indicated for prophylaxis, as well as the newer macrolides, clarithromycin and azithromycin. Duration varies with drug given and ranges from 7-14 days. Steroids and albuterol do not have a documented effect in reducing paroxysms of coughing.

Immunization plays an important role in prevention of disease. Pertussis vaccine was originally recommended in 1947. After that, a 150-fold reduction in attack rate was noted(4). Currently 2 types of pertussis vaccine are available: whole cell (DTP) and acellular (DTaP). Because of the lower frequency of adverse events, DTaP is now the recommended vaccine. Current acellular pertussis vaccine components include pertussis toxin and FHA. A few vaccines also include pertactin (prn) and fimbriae (FIM). Precise antibodies that result in protection are still not clearly defined, hence the different types and amounts of components. Adult formulations of acellular pertussis vaccine have been found to be safe and immunogenic in adults and adolescents, but are still in clinical trials(5) (6).

The CDC has made a year 2000 goal of <1000 cases of pertussis. In order to come close to achieving this goal, it is important to consider pertussis as the etiologic agent responsible for prolonged cough in adolescents and adults as well as in children. The disease in adults is often atypical and since pertussis is believed to be primarily a disease of childhood, it is not often considered. While not a serious disease in these older groups, documentation is important since they can transmit the disease to children and infants not yet protected by the vaccine. By increasing awareness of adult disease, it is speculated we could prevent childhood disease.
We have seen 7 cases of pertussis in hospitalized patients in the past 2 years. One infant, born to a mother with a 2 week history of cough presented with apnea and died. Another 4 month old baby was admitted for failure to thrive and during the history, the mother revealed post-tussive vomiting in the infant. She also reported an older child (18 years) with a 3 week history of cough. Pertussis was found to be the etiologic agent in both cases.

References

1. Centers for Disease Control and Prevention. Pertussis vaccination: acellular pertussis vaccine for the fourth and fifth doses of the DTP series. MMWR Morb Mortal Wkly Rep 1995; 44:525-529.

2. Bisgard K et al. In "Program and abstracts of the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy": American Society of Microbiology, 1998

3. Wright, Seth W. Pertussis infection in adults. Southern Medical Journal 91(8):702-8, 1998 August.

4. Feigin, Ralph and Cherry, James. Textbook of Pediatric Infectious Diseases. Fourth Edition. WB Saunders Philadelphia 1998.

5. Halperin, SA, Smith, B, Barretto L et al. A 5 Component Adult Formulation Acellular Pertussis Vaccine in Safe and Immunogenic in Adolescents and Adults. In "Program and abstracts of the 36th Annual Meeting of the Infectious Diseases Society of America", Denver, 1998:89.

6. Van Damme P, Joosens E, Vellinga A. A diphtheria-tetanus-acellular pertussis vaccine for adults (abstract #703). In "Program and abstracts of the 36th Annual Meeting of the Infectious Disease Society of America", Denver, 1998:208.
Volume 14, Number 1 - January-February Newsletter

RSV continued to predominate in Syracuse in January with 18 hospitalized children having positive RSV washes. The first documented influenza patient was a 22 month old on 1/17/99 being screened for our influenza study. Five other children (10 months - 15 years) were also diagnosed with influenza A (H3N2 Sydney-like) in January. Interestingly, three of these patients whom we were consulted on, were neutropenic with ANC < 1000. We continued to see a few cases of adenovirus each month. Surprisingly, one 3 year old child had enteroviral meningitis in January. A 10 year old girl admitted with transverse myelitis was culture positive for Mycoplasma pneumoniae.

In February, 40 children admitted through the emergency room were positive for RSV. Influenza A was diagnosed in 5 children (35 days - 4 years) admitted with fever and/or rule out sepsis. Influenza B appeared on the scene 2/8/99 in 2 patients; one, a 10 year old boy with immunodeficiency and the other a 20 month old with gastroenteritis. Two infants (22 days and 79) admitted with rule out sepsis had rhinovirus. Two siblings seen in our ID clinic had adenovirus.

So far, in March there have been no cases of Influenza A; however, a 70 day old was admitted to the Pediatric Intensive Care Unit with Influenza B and RSV. Rhinovirus was isolated from 3 patients admitted with rule out sepsis (27 days, 73 days and 8 months).

We would like to thank the Virology Clinical Laboratory personnel at University Hospital for their continued assistance in providing the information for this newsletter.

We would like to acknowledge the Pediatric Society of Onondaga County for their contribution in support of this newsletter