Pertussis caused by -Bordetella pertussis and B. parapertussis
Pertussis is an acute respiratory tract infection . pertussis =intense cough
Etiology
Bordetella pertussis is the only cause of epidemic pertussis and the usual cause of
sporadic pertussis.
B. parapertussis is an occasional cause of Pertussis
B. pertussis and B. parapertussis are pathogens of humans
B. bronchiseptica is an animal pathogen;
Protracted coughing can be caused by
Mycoplasma ,
parainfluenza or influenza viruses,
enteroviruses,
respiratory syncytial virus,
adenoviruses.
Epidemiology.
Sixty million cases of pertussis a year occur worldwide, with more than half a million
deaths.
Pertussis is endemic, with epidemic cycles every 3-4 yr
cases occur from July through October.
Pertussis is extremely contagious, with attack rates as high as 100% in susceptible
individuals exposed to aerosol droplets at close range.
B. pertussis does not survive in the environment.
Neither natural disease nor vaccination provides complete or lifelong immunity against
reinfection or disease.
Protection against typical disease begins to decrease 3-5 yr after vaccination
Can infect elderly,
Coughing adolescents and adults (usually not recognized as having pertussis) are the
major reservoir for B. pertussis and are the usual sources for "index cases" in infants and
children.
Pathogenesis
gram-negative coccobacilli
grow aerobically on starch blood agar
pertussis toxin (PT), the major virulence protein.
Other toxins are Tracheal cytotoxin, dermonecrotic factor, and adenylate cyclase
These toxins are responsible for the epithelial damage that produces respiratory
symptoms
Pertussis toxin has histamine sensitivity, insulin secretion, leukocyte dysfunction and
causes systemic manifestations of disease.
PT causes lymphocytosis
Clinical manifestations
3 stages -
catarrhal,
paroxysmal,
convalescent stages, each lasting 2 wk.
incubation period from 3-12 days,
catarrhal symptoms of congestion and rhinorrhea,
low-grade fever,
sneezing, lacrimation, and conjunctival suffusion.
coughing begins -intermittent, paroxysms that are the hallmark of pertussis.
infant begins to choke, gasp, and flail extremities, eyes watering and bulging, face
reddened.
Whoop (forceful inspiratory gasp) - chin and chest held forward, tongue protruding
maximally, eyes bulging and watering, face purple, - loud whoop follows as inspired air
traverses the still partially closed airway.
Post-tussive vomoting is common -clue to the diagnosis
Post-tussive exhaustion
Immunized children also have similar phases
Findings on physical examination
Conjunctival hemorrhages and petechiae on the upper body
Diagnosis
pure or predominant complaint of cough,
fever, malaise or myalgia, exanthem or enanthem, sore throat, hoarseness, tachypnea,
wheezes, and rales ARE ABSENT
young infants with "afebrile pneumonia,"
B. pertussis is associated with staccato cough (breath with every cough),
cough of 14 or more days' duration
paroxysms, whoop, or post-tussive vomiting
contact with pertussis,
Apnea or cyanosis (before appearance of cough) is a clue in infants younger than 3 mo.
Some times - sudden infant death.
1. Adenoviral infections = fever, sore throat, and conjunctivitis.
2. Mycoplasma = episodic coughing, history of fever, headache, and systemic
symptoms, rales on auscultation of the chest.
3. Chlamydia trachomatis = purulent conjunctivitis, tachypnea, rales or wheezes
4. respiratory syncytial virus = predominant lower respiratory tract signs
Leukocytosis (15,000-100,000 cells/mm3 ) due to absolute lymphocytosis is a
characteristic in late catarrhal and paroxysmal stages.
Absolute increase in neutrophils suggests a different diagnosis or secondary bacterial
infection.
hypoglycemia is reported occasionally.
The chest radiograph =
1. perihilar infiltrate or edema (sometimes with a butterfly appearance) and variable
atelectasis.
2. Parenchymal consolidation suggests secondary bacterial infection.
3. Pneumothorax, pneumomediastinum, and air in soft tissues
sensitive and specific method of diagnosis =direct fluorescent antibody (DFA) testing of
nasopharyngeal secretions
Culture results are positive during the catarrhal stage
Treatment
limit the number of paroxysms
nutrition, rest, and recovery without sequelae
goals of hospitalization are to
(1) assess progression of disease and likelihood of life-threatening events at peak
of disease,
(2) prevent or treat complications,
(3) educate parents in the natural history of the disease and in care that will be
given at home.
Heart rate, respiratory rate, and pulse oximetry are monitored
feeding, vomiting, and weight
provide oxygen, stimulation, or suctioning
life-threatening events require intubation, paralysis, and ventilation.
Feeding -Large-volume feedings are avoided.
Apnea and seizures may occur during paroxysm
Antimicrobial Agents
Erythromycin, 40-50 mg/kg/24 hr PO in four divided doses (maximum 2 g/24 hr) for 14
days
clarithromycin (10 mg/kg/24 hr) divided into two doses for 7 days;
azithromycin (10 mg/kg/24 hr) once a day for 5 days
Ampicillin, rifampin, and trimethoprim-sulfamethoxazole
erythromycins are superior to amoxicillin and are the only agents with proven efficacy.
Salbutamol may reduce symptoms
Corticosteroids. = Usefulness not proved
Pertussis Immune Globulin.
intravenous immunoglobulin is not recommended for treatment of pertussis.
Isolation.
Patients are placed in isolation for at least 5 days after initiation of erythromycin therapy.
Care of Household and Other Close Contacts.
Erythromycin, 40-50 mg/kg/24 hr PO in four divided doses (maximum 2 g/24 hr) for 14
days should be given promptly to all household contacts and other close contacts, such as
those in daycare, regardless of age, history of immunization, or symptoms.
contacts younger than 7 yr who are underimmunized should be given a pertussis-
containing vaccine
Complications
younger than 6 mo have excess mortality and morbidity.
pneumonia
seizures
encephalopathy
apnea,
secondary infections (such as otitis media and pneumonia),
physical sequelae of forceful coughing.
Apnea, cyanosis, and secondary bacterial pneumonia are events leading to intubation and
ventilation.
Bacterial pneumonia or adult respiratory distress syndrome is the usual cause of death at
any age;
pulmonary hemorrhage
Fever, tachypnea or respiratory distress between paroxysms, and absolute neutrophilia are
clues to pneumonia. Expected pathogens include Staphylococcus aureus, S. pneumoniae ,
and bacteria of mouth flora.
Bronchiectasis after pertussis.
Increased intrathoracic and intra-abdominal pressure during coughing = conjunctival and
scleral hemorrhages, petechiae on the upper body, epistaxis, hemorrhage in the central
nervous system (CNS) and retina, pneumothorax and subcutaneous emphysema, and
umbilical and inguinal hernias.
Laceration of the lingual frenulum
Rectal prolapse, due to pertussis in malnourished children
dehydration and malnutrition due to vomiting
Tetany due to post-tussive vomiting and alkalosis.
CNS abnormalities - result of hypoxemia or hemorrhage
Apnea or bradycardia causes hypoxia
Seizures - hypoxemia, hyponatremia from excessive secretion of antidiuretic hormone ,
hypoglycemia, a direct effect of PT, and secondary infection due to virus ,parenchymal
hemorrhage and ischemic necrosis.
Prevention
Universal immunization of children with pertussis vaccine, beginning in infancy,
Whole-Cell Vaccine
Diphtheria and tetanus toxoids combined with whole-cell pertussis (DTP) vaccine -
prepared from suspension of inactivated B. pertussis bacterial cells-70-90% effective in
preventing pertussis disease.
adverse effects
local (e.g., erythema, swelling and pain at the injection site),
fever,
systemic events (e.g., fretfulness, drowsiness, and anorexia).
serious systemic events (e.g., seizures and hypotonic hyporesponsive episodes)
occur in 1/1,750 doses
Acute encephalopathy 1-10 cases in 1 million doses administered
Acellular Vaccine
diphtheria and tetanus toxoids combined with acellular pertussis (DTaP) vaccines
fewer adverse reactions.
Pertussis Toxin is detoxified either chemically or using molecular genetic techniques.
Mild local and systemic adverse effects - high fever, persistent crying of 3 hr or longer
duration, hypotonic hyporesponsive episodes, and seizures occurred less in those who
received DTaP compared with DTP vaccine
Acellular pertussis vaccines are used only upto 6 yr of age.
Source:DR.NS.MANI.MD Associate Professor in Pediatrics
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