Bordetella is tiny gram-negative coccobacilli and causes PERTUSSIS (Whooping Cough). Pertussis is extremely contagious, with attack rates as high as 100% in susceptible individuals exposed to aerosol droplets at close range. Incidence is highest in children aged 1-5 years. Neither natural disease nor vaccination provides complete or lifelong immunity.
Although it initially resembles an ordinary cold, whooping cough may eventually turn more serious, particularly in infants. In the more advanced stages, it's marked by a severe, hacking cough followed by a high-pitched intake of breath that sounds like "whoop."
Protection against typical disease begins to wane 3-5 years after vaccination. Coughing adolescents and adults are the major reservoir for B. pertussis. Adherence of B. pertussis to respiratory epithelium is required for the pathogenesis of whooping cough. The incubation period is 3-12 days.
Transmission and epidemic of whooping cough (Pertussis):
Pertussis is usually spread by infected respiratory droplets from the coughs and sneezes of people who have the infection. Infants younger than 1 year are most susceptible and have the most severe symptoms, but teenagers and adults may also contract milder cases of pertussis that are often mistaken for bronchitis. There is a danger that people with less severe, undiagnosed cases may spread the infection to infants who have not yet been immunized.
According to a multi-country study led by researchers from the University of North Carolina at Chapel Hill School of Public Health found ((Mar. 27, 2007) that parents were the source of pertussis, commonly known as whooping cough, in 55 percent of infants. In all, household members including siblings, aunts and uncles, cousins and grandparents were responsible for 75 percent of pertussis cases among infants for whom a source could be identified.
The incidence of whooping cough has been increasing, primarily among children too young to have completed the full course of vaccinations and teenagers whose immunity has faded. It's characterized by severe coughing spells that end in a "whooping" sound when the person breathes in. Before a vaccine was available, pertussis killed 5,000 to 10,000 people in the United States each year.
Now, the pertussis vaccine has reduced the annual number of deaths to less than 30. But in recent years, the number of cases has started to rise. This increase is due to an epidemic of pertussis in adolescents and adults who have lost their immunity from their childhood vaccines and need a booster vaccine. While this population has less severe consequences from the infection, they are the source of its spread to infants who are too young to be protected by their own vaccinations.
Among all pertussis hospitalizations during 1994-2003 in children under age 2 years, 92% occurred in infants under 6 months of age. This suggests that children too young to receive immunization or to have developed adequate protection from immunization are most likely to be hospitalized for pertussis.
In a 2003-2004 outbreak of whooping cough in Fond du Lac County, Wisconsin, most cases were diagnosed in adolescents, although adults had more severe disease, public health officials report in the Archives of Pediatric and Adolescent Medicine for January, 2008.
After the first cases were reported to the Fond du Lac Health Department in late July 2003, the origin of the outbreak of whooping cough, also referred to as pertussis, was traced to a high-school weight room that was used before the school year started.
"Enhanced surveillance for pertussis, contact identification, diagnostic testing, treatment, and antibiotic prophylaxis were initiated in the community," Dr. Jeffrey P. Davis, of the Wisconsin Division of Public Health in Madison, and colleagues report. Individuals who were infected were requested to stay home during the first 5 days of antibiotic treatment.
The first phase of the outbreak peaked during mid-June to mid-August, but between October and early December, the number of cases again rose sharply, with substantial transmission to adults and children in the community.
Overall, 71 percent of infected patients were between 10 and 19 years of age. Fourteen percent of the cases occurred in patients who were 2 months to 9 years of age and 15 percent occurred in adults. The two infants with pertussis required hospitalization. Adults reported a higher frequency of exacerbations and vomiting than did adolescents. Davis and colleagues note that patients were diagnosed with pertussis at all 20 public schools in the county.
Signs, symptoms and Clinical manifestations:
Pertussis is typically a prolonged illness, with an average duration of 6-8 weeks. The symptoms generally evolve through three stages: i) catarrhal, ii) paroxysmal, and iii) convalescent stages each lasting 2 weeks. The catarrhal symptoms are non-specific and include coryza, mild cough, lacrimation, malaise and low grade fever.
In the paroxysmal stage, the cough gradually becomes more severe and violent and assumes a paroxysmal character. The child started a burst of uninterrupted coughs, chin and chest held forward, tongue protruding maximally, eyes bulging and watering, until at the seeming last moment of consciousness, coughing ceases and a loud whoop follows as inspired air traverses the still partially closed airway. The episode may end with expulsion of a thick plug of inspissated tracheal secretions. Post-tussive emesis is common and is a major clue to the diagnosis. As paroxysmal stage fades into convalescence, the number, severity, and duration of episodes diminish. The physical examination is generally uninformative.
Diagnosis and Complications:
Pertussis should be suspected when cough is predominant in the absence of- fever, malaise or myalgia, exanthem or enanthem, sore throat, wheezes, and rales (wet, crackly lung noises heard on inspiration). Leukocytosis (15,000-100,000 cells/cmm) due to absolute lymphocytosis is a characteristic in late catarrhal and paroxysmal stage. Absolute increase in neutrophils suggests a different diagnosis or secondary bacterial infection. Isolation of B. pertussis in culture remains the standard, more sensitive and specific method of diagnosis than direct fluorescent antibody (DFA) testing of nasopharyngeal secretions.
Protracted coughing can be caused by mycoplasma, parainfluenza or influenza viruses, enteroviruses, respiratory syncytioal virus, or adenoviruses. Cystic fibrosis and recurrent tracheobrnchial aspiration may be associated. The common complication are-
i) Apnea,
ii) Secondary infections (such as otitis media and pneumonia),
iii) Conjunctival hemorrhage,
iv) Rectal prolapse,
v) Ulcer of the lingual frenulum,
vi) Malnutrition,
The rare complications include encephalopathy, convulsions, pulmonary hemorrhage, Bronchiectasis, pneumothorax, SIADH. Infants under 6 months of age have excessive mortality and morbidity.
Treatment:
1) Antimicrobial agents: An antimicrobial is used for potential clinical benefit and to limit the spread of infection. Erythromycin, 40-50mg/kg/24 hr, orally in four divided doses (maximum 2 g/d 24 hr) for 14 days is standard treatment.
2) Supportive: All children below one year of age should be admitted in hospital. Heart rate, respiratory rate are monitored and provide oxygen. Feeding should be small and frequent.
During recovery, let your child rest in bed and use a cool-mist vaporizer. This will help loosen respiratory secretions and soothe irritated lungs and breathing passages. (If you use a vaporizer, be sure to follow directions for keeping it clean and mold-free, usually with small amounts of bleach.) In addition, try to keep your home free of irritants that can trigger coughing spells, such as aerosol sprays, tobacco smoke, and smoke from cooking, fireplaces, and wood-burning stoves.
3) Control measures:
a) Isolation: The patient is placed in respiratory isolation for at least 5 days after initiation of erythromycin therapy.
b) Contact prophylaxis: Erythromycin for 14 days should be given to all contacts regardless of age, history of immunization, or symptomatology. Not routinely recommended for exposed health care workers.
c) Immunization: Close contacts younger than 7 years who are under immunized should be given a pertussis-containing vaccine, with further doses to complete recommended series. Children younger than 7 years, who received a 3rd dose, 6 months or more before exposure, or a 4th dose 3years or more before exposure, should receive a booster dose.
Prevention:
Universal immunization of children with pertussis vaccine. The vaccine currently used is a killed whole cell vaccine composed of a suspension of inactivated B. pertussis, combined with diphtheria and tetanus toxoid and aluminum-containing adjuvant. Purified component acellular pertussis (aP) vaccines, are immunogenic and associated with fewer adverse events when compared with DTP.
Whooping cough can be prevented with the pertussis vaccine, which is part of the DTaP (diphtheria, tetanus, acellular pertussis) immunization. DTaP immunizations are routinely given in five doses before a child's sixth birthday. Without vaccine protection, people can easily contract and transmit this infectious disease. Routine immunization with pertussis vaccines has greatly reduced illness and deaths associated with the disease.
Though the widespread use of vaccines has helped reduce disease drastically, recent surveys reveal that the disease is increasingly being diagnosed in a large number of vaccinated adults, posing a serious health risk to unvaccinated children and infants.
The CDC says that between 1996 and 2004 the majority of pertussis patients were either too young to have the required vaccine series or too old to have been immunized.
“Ongoing research demonstrates that adolescents and adults can transmit pertussis to infants. "Pertussis immunization of adolescents and adults, especially those in contact with young infants would not only protect themselves form pertussis, but would also protect young infants from pertussis and could save lives,” experts advised.
According to a study funded by The Centers for Disease Control and Prevention suggested (Sep. 7, 2007) that In addition to the HPV or the human papillomavirus vaccine, two other vaccines have been added to the immunization schedule for adolescents: Tdap to protect against tetanus, diphtheria and pertussis (whooping cough) and meningococcal vaccine for viral meningitis, in addition to a new recommendation for a varicella (chicken pox) booster. Each of these vaccines are given in a single shot each and don’t require subsequent visits.
According to the study by public health officials report in the Archives of Pediatric and Adolescent Medicine stated; "In most cases, vaccination histories were up to date to the standards at that time, 84 percent having received at least five doses. However, it wasn't until 2005 that pertussis booster vaccines were licensed for use in teenagers and adults". "This labor- and resource-intensive outbreak highlights potential benefits of pertussis booster vaccination among adolescent and adult populations," the authors concluded.
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