Pertussis overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Luke Rusowicz-Orazem, B.S.
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Overview
Pertussis, also known as whooping cough, is a highly contagious disease caused by the bacterium Bordetella pertussis. The name is derived from a characteristic severe hacking cough, followed by a high-pitched intake of breath with a "whoop" sound. A similar, milder disease is caused by B. parapertussis.[1] Worldwide, there are 30–50 million pertussis cases and approximately 300,000 deaths per year.
Despite generally high coverage with the DTP and DTaP vaccines, pertussis is one of the leading causes of vaccine-preventable deaths world-wide. The majority of deaths occur in young infants who are either unvaccinated or incompletely vaccinated; three doses of the vaccine are necessary for complete protection against pertussis. Ninety percent of all cases occur in the developing world. However, in the winter of 2006, a New York school district suffered a large pertussis outbreak with greater than thirteen falling victim to the infection. In the fall of 2006, a pertussis outbreak struck New Trier High School, a public school in Winnetka, Illinois, with twenty-four high school students catching the disease. In response, the Cook County Department of Public Health provided the vaccine, free of charge, to eligible students.
Historical Perspective
The first description of Pertussis dates back to the 12th century. The earliest outbreaks of Pertussis were recognized by Bahaodwole Razi in 1502 in Persia and by Guillaume de Baillou in 1578 in France. Bordetella pertussis was first isolated by Jules Bordet and Octave Gengou in 1906. Bordet and Gengou developed the first vaccine and serological test for Pertussis. In the 1940s, Grace Elderling, Loney Gordon, and Pearl Kendrick cocmbined diphtheria and tetanus with the pertussis and develop the first combination DTP vaccine. In response to adverse side effects of DTP, a safer, acellular DTaP vaccine was created in Japan in 1981.
Pathophysiology
Pertussis is primarily a toxin-mediated disease. Bordetella pertussis is usually tansmitted to the human host by direct contact with aerolized mucus of infected individials. B. pertussis attaches to the cilia of the respiratory epithelial cells, proliferates and produces virulence factors that paralyze the cilia, and causes inflammation of the respiratory tract, which interferes with the clearing of pulmonary secretions. B. pertussis utilizes virulence factors - including pertussis toxin (PT), filamentous hemagglutinin (FHA), fimbriae (FIM), adenylate cyclase toxin (ACT), trachael cytotoxin (TCT), lipooligosaccharide (LOS), and dermonecrotic toxin (DNT) - to attach, proliferate, and and evade the host immune system.[2][3]
Causes
Bordetella pertussis is a Gram-negative, aerobic, non-motile, non-spore-forming coccobacillus. It is the pathogen responsible for pertussis (whooping cough). Unlike B. bronchiseptica, B. pertussis is not motile. Humans are the only known reservoir for B. pertussis. The lipopolysaccharide-containing outer membrane of B. pertussis is unique and contains a different phosphate composition from other bacterial outer membranes.
Differential Diagnosis
Pertussis must be differentiated from other causes of cough, dyspnea, and coryza, such as asthma, pneumonia, bronchiolitis, croup, common cold, cystic fibrosis, foreign body aspiration, gastroesophageal reflux disease, and sinusitis.
Epidemiology and Demographics
In the United States, the incidence of pertussis is approximately 1.5 to 3.0 per 100,000 individuals, with approximately 5,000 to 7,000 cases reported annually. The incidence of pertussis is thought to be on the rise due to the decline in vaccination rate and diminished herd immunity. Infants and young children < 5 years of age are more commonly infected with pertussis than adults. There is no gender predilection for the development of pertussis. Pertussis-related deaths are rare, but are more common in developing countries, among infants < 6 months of age, and among adult patients with significant co-morbidities.
Risk Factors
Risk factors in the development of pertussis include no or incomplete vaccination against pertussis, exposure to infected individuals, infants or children < 5 years of age, and immunocompromised status.
Natural History, Complications and Prognosis
The clinical course of the illness is divided into three stages: catarrhal, paroxysmal and convalescent. If left untreated, the majority of patients with clinical manifestations of pertussis develop and fever coryza (runny nose, occasional cough) for 1-2 weeks, followed by paroxysmal fits of whooping cough that may last 1-6 weeks before finally recovering from the disease. Compared with children, adolescents and adults usually experience a milder course of the disease, and the characteristic whooping cough may be absent. Unvaccinated or incompletely vaccinated infants younger than 12 months of age have the highest risk for developing severe infection and life-threatening complications and death.[4] Complications of pertussis include apnea, pneumonia, seizure, and death.
Diagnosis
History and Symptoms
After a two day incubation period, pertussis in infants and young children is characterized initially by mild respiratory infection symptoms such as cough, sneezing, and runny nose (catarrhal stage). After one to two weeks, the cough changes character, with paroxysms of coughing followed by an inspiratory "whooping" sound (paroxysmal stage). Coughing fits may be followed by vomiting due to the sheer violence of the fit. In severe cases, the vomiting induced by coughing fits can lead to malnutrition. The fits that do occur on their own can also be triggered by yawning, stretching, laughing, or yelling. Coughing fits gradually diminish over one to two months during the convalescent stage.
Physical Examination
Physical examination adds less to the diagnosis. Conjunctival hemorrhage may be noticed due to intense coughing.
Treatment
Medical Therapy
Treatment with macrolide antibiotic shortens the duration of infection. If macrolides are ineffective co-trimoxazole is administered.
Primary Prevention
Childhood vaccination is highly effective in preventing pertussis. Routine childhood vaccination in the United States is performed with the DTaP vaccine (acellular pertussis vaccine combined with tetanus and diphtheria toxoids).
References
- ↑ Finger H, von Koenig CHW (1996). Bordetella–Clinical Manifestations. In: Barron's Medical Microbiology (Barron S et al, eds.) (4th ed. ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1.
- ↑ Pertussis (whooping cough). CDC.gov. Accessed on June 15th, 2014
- ↑ Hewlett EL, Burns DL, Cotter PA, Harvill ET, Merkel TJ, Quinn CP; et al. (2014). "Pertussis pathogenesis--what we know and what we don't know". J Infect Dis. 209 (7): 982–5. doi:10.1093/infdis/jit639. PMC 3952676. PMID 24626533.
- ↑ Pertussis (whooping cough). CDC.gov. Accessed on June 15, 2014