Whooping Cough

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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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