Pertussis or Whooping Cough

CASE:
A 3-month-old infant has a six days history of a mild cough. There are thick nasal secretions, poor feeding but no fever. In the last 10 hours, she has developed spasmodic coughing with vomiting (posttussive emesis) and cyanosis(apnea). She is losing weight. There is no examination finding during the coughing spells. The chest radiograph shows peribronchial thickening. Complete blood count reveals 30,000 white blood cells with 95% lymphocytes(lymphocytosis).

What are your diagnosis and management?.

Pertusses (means an intense cough) is caused by Bordetella Pertussis( a gram-negative Cocco-bacilli) is a highly infectious disease of the respiratory tract affecting the susceptible children under 2 years of age.
Bordetella parapertussis( in 5% of the case), Bordetella bronchiseptica, and adenovirus may cause the same illness, but less severe and short duration (pertussis-like illness or pertussis syndrome).
There is no cross-immunity among the organisms and this probably accounts for the second attack of a whooping cough

Epidemiology:

Pertussis is highly contagious.
Attack rates are almost 100% in susceptible individuals.
Humans are the only host of B.Pertussis.
Transmission is by droplet during a severe cough.
The incubation period is between 3-12 days.
The infectivity is during the first four weeks of the illness. Patients are the most contagious during the pre paroxysmal stage.
It occurs in all ages but most common and most severe in under the age of 5 years and the mortality rate is highest amongst the infants below 1 year of age. There is a little seasonal variation.
Immunization reduces the incidence and mortality rate of pertussis. Active immunization follows natural pertussis. Neither natural disease nor the vaccination provides the life long immunity. Reinfection may occur a year later but it is milder. Immunity following immunization decrease in 3-5 years and undetectable after 12 years.
Intra Family spread is common among children usually acquire the disease from symptomatic family contacts. In the adult, the syndrome is atypical with a severe cough but no whoop.
Carriers of B.Pertussis are found frequently but the person previously immunized have been shown during outbreaks of disease to excrete the organism in the absence of clinical symptoms or in the presence of mild or atypical illness.

Pathology

B. Pertussis adheres to the ciliated epithelial cells of the respiratory tract and multiplies there without invading the tissue.
The bacteria produce an endotoxin, which causes tissue necrosis but a major virulence factor is exotoxin Pertussis Toxin (PT).PT is the main cause of lymphocytosis observed in the case of pertussis.
The inflammation of the respiratory mucosa from the nasopharynx to the bronchioles, causing patchy necrosis of the superficial epithelium, which is covered by the tenacious mucopurulent exudate containing masses of bacteria.
The lumen of the bronchioles may become obstructive either causing obstructive emphysema or atelectasis or bronchiectasis may occur.

The peri-hilar infiltrates produce the ''shaggy'' heart border on chest X-Ray that is characteristic of Pertussis.
Cerebral haemorrhage and fatty infiltration of the liver may occur.

Clinical Findings:

Clinical manifestations depend on the

Specific pathogen
Patients age
Host Immunization status

The younger the child, the more atypical the signs and symptoms of the disease.
Infants less than 6 months of age may have apnea, cyanotic spells, and cough but no whoop.
The stages are recognised as catarrhal, paroxysmal and convalescent stage. Each stage lasts about two weeks but the duration may vary according to the severity of the illness.

Catarrhal Stage: ( Prodromal or Pre-paroxysmal stage)(1-2 weeks)

Symptoms are indistinguishable from those of a mild upper viral respiratory infection.
There is coryza (clear or mucoid rhinorrhea) with sneezing, conjunctival redness, and lacrimation.
There is low-grade fever wheezing and mild cough.
The diagnosis is difficult at this stage and the child is most infectious.

Paroxysmal Stage:( 2-4 weeks or longer)

The episodes of coughing increase in an effort to expel the bronchial exudate.
After a series of coughing during a single expiration, there is a sudden massive inspiratory effort, which produces a whoop(air is inhaled forcefully against a narrowed glottis). The paroxysm may last half a minute or more and toward the end child's face becomes red or even blue, the eyes protrude and neck veins get engorged and the appearance of being strangled.
Posttussive exhaustion is common. Vomiting may occur following a bout of paroxysm and should raise the suspicion of pertussis.
The infant usually doesn't produce a whoop but they tend to get chocked and may become intensely cyanosed.
An infant with potentially fatal pertussis may appear completely well between episodes.
During this stage, the infant may lose weight as a result of exhausting recurrent episodes of a cough., poor appetite and may become dehydrated.
In spite of respiratory symptoms, there are no abnormal physical signs in the chest except occasional rhonchi.

Convalescent stage:(1-2 weeks)

During this stage episodes of cough becomes less frequent and less severe and paroxysm of whooping disappear.
The child's appetite improves but cough may persist in some patients for several months until full recovery occurs.
Pertussis may occur in a mild form as a persistent cough in children who are immunized against this disease.

Complications:

Bronchopneumonia (in 25% of cases) due to B.pertussis itself or from secondary bacterial infection (H. influenzae, Pneumococcus, S. aureus) is the most common complication. It is responsible for more than 90% of deaths in infants. It is characterized by abrupt deterioration during the paroxysmal stage, associated with high fever and a striking leukemoid reaction with a shift to predominantly polymorphonuclear leukocytes.
Atelectasis due to mucus plug and later bronchiectasis.
Interstitial and subcutaneous emphysema.
Otitis media and sinusitis are usually due to pneumococcus.
Convulsions (in 4% of infants) and coma may occur. Convulsions are particularly common in young infants and may lead to temporary or permanent neurological defects. There may be tetanic seizures induced by alkalosis which is induced by persistent vomiting.
Encephalitis ( in 1% of infants) may follow the attack of pertussis or immunization.
Rarely, Epistaxis, retinal and subconjunctival haemorrhages and rupture of the diaphragm may occur. This is due to increased intra-thoracic pressure and venous engorgement.
Rupture of the frenulum may occur during the paroxysm.
Rental prolapse and umbilical or an inguinal hernia may occur.
Reactivation of quiescent tuberculosis may occur due to depression of the cell-mediated immunity. It is advisable to give prophylactic INH for 3 months in patients who have pertussis.
Malnutrition may follow.
Apnea and sudden death may occur during a severe paroxysm.
The forceful bout of cough may rupture the alveoli and produce pneumo-mediastinum, pneumothorax or interstitial or subcutaneous emphysema.
Recurrent vomiting can lead to metabolic alkalosis or malnutrition.

Diagnosis:

Clinical diagnosis is only obvious during the paroxysmal stage.
There is a little difficulty in making the clinical diagnosis of whooping cough in a patient who, after a period of coryzal symptoms develops paroxysmal coughing (especially of more than 14 days duration) with a terminal inspiratory whoop or posttussive vomiting. There is only a pure or predominant complaint of cough, especially if these features are absent: fever, malaise or myalgia, exanthem or ananthem, sore throat, hoarseness, tachypnea, wheezes and rales.
In infants younger than 3 months of age, apnea or cyanosis may be the clue of the disease. No or slight fever may be present. Temperature greater than 101F suggests bacterial super-infection or another cause of respiratory tract infection.
A history of incomplete vaccination or a history of contact with a pertussis patient helps.
In early stages, diagnosis can be confirmed by laboratory tests.

Blood Counts:

There is a leukocytosis. Count varies between 15,000 to 100,000 cells/mm3 with 70-80% leukocytes(absolute lymphocytosis) near the end of the catarrhal stage and during the paroxysmal stage.
In viral infections, there are large atypical lymphocytes but in pertussis, lymphocytes are normal small cells of T-cell or B-cell origin. This type of lymphocytes may not be present in younger infants and partially vaccinated children. The blood picture may resemble lymphocytic leukaemia (leukemoid reaction).
Polymorphonuclear leukocytosis suggests a secondary bacterial complication. Fluorescent antibody staining of nasopharyngeal secretions may provide a rapid and specific diagnosis if directly available.

Culture:

In early stages, diagnosis can be confirmed by swab which is cultured on Bordet-Genou media at the bedside.
A sterile cotton swab wrapped about a flexible copper wire is passed through nares, and mucus is obtained from the posterior pharynx. B.pertussis is readily killed by desiccation, so specimen should be quickly plated onto fresh medium. The cough plate is inferior to nasopharyngeal swabs but may give positive cultures during the first two weeks of illness. During the early stages, B.pertussis can be isolated from 90% of the patients.
By the third or fourth week the organism can be recovered in only 50% of the cases, and in the convalescent stage, it is unusual to obtain a positive culture.

X-ray Chest:

It shows peri-hilar infiltrates, a shaggy border of heart, atelectasis or emphysema.
It helps in excluding the complications e.g atelectasis.

Differential Diagnosis:

Bronchiolitis
Pneumonia due to chlamydia, bacteria or cytomegalovirus.
Cystic fibrosis
Tuberculosis
Asthma
Intra-thoracic lymphadenopathy compressing trachea and bronchi.
Foreign body inhalation.

Management:

Specific Measures:

Erythromycin 30-50mg/kg/day in 3 divided doses (maximum 2g/day) is given for a period of 14 days. Antibiotics may be given in order to make patient non-infectious. Treatment for less than 14 days may result in bacteriologic relapse.
Azithromycin (10mg/kg/day once a day for 5 days) or clarithromycin (15mg/kg/day divided into two doses for 7 days) are also equally effective.
The most valuable part of antibiotic therapy is the prevention and treatment of secondary bacterial infections. The drug of choice is penicillin G, although it has no effect on Bordetella Pertussis itself.
In severe cases, corticosteroids and salbutamol nebulization may be effective.

General Measures:

Young infants particularly those under 6 months of age should be hospitalized.
It is important to maintain adequate hydration and nutrition. Frequent small feedings are recommended. Nasogastric tube feeding and parenteral fluids may be necessary in severe cases.
Oxygen and gentle suction may be needed to remove profuse, viscid secretions. The child's posture should be adjusted to allow him to get rid of his secretions.
Sedation and cough mixtures play a minor part.
Avoid mist therapy.
Convulsions are treated by injectable diazepam or oral phenobarbitone.
Isolate the patient for the first 5 days of therapy.

Prevention:

There is a lack of placental immunity, so infants are highly susceptible to infection. The pertussis vaccine is given as a part of the DPT vaccine.
Erythromycin is effective in preventing the disease in exposed neonates and children.
Close contacts of less than 7 years of age who have completed four doses of DPT vaccine should receive a booster dose of DPT if three years have passed since the last booster dose of DPT. They should also be given erythromycin.
Close contacts or more than 7 years of age need no vaccination. They should receive erythromycin as prophylaxis for 10-14 days.

Prognosis:

The mortality rate is less than 1%.
In infants, less than 5 months of age mortality rate may be up to 40%. So in endemic or epidemic areas of the disease, the vaccine may be given at the age f two weeks,
Cause of death in most cases is pneumonia, other pulmonary complications, asphyxia, or encephalopathy.