Pertussis  

by Carmen Cardenas

 

Etiology and History

Pertussis is caused by Bordetella pertussis. Bordetella pertussis was first recognized by Bordet and Gengou in 1906. The genus Bordetella is known for five different species that cause respiratory disease in humans and animals. The five species are as follows, B. pertussis B parapertussis, B. bronchi septica, B. avium and B hinzu. [1] Pertussis has been on the rise since the 1980’s [3] Its increase in occurrence has caused concerns for healthcare providers, policy makers and every day folks. A diagnosis of pertussis has multiple long-term ramifications. Parents and patients have to deal with long term medical complications and the financial difficulties that a diagnosis of pertussis involves. The average hospital bill for an unvaccinated individual hospitalized with pertussis is $12,940.00 and $7,845.00 dollars per vaccinated person. [2]

Microbial Characteristics and Virulence

Bordetella pertussis is a non-motile aerobic gram negative coccobacillis bacterium capable of hemolysis. [2] [4] B. pertussis measures approximately 0.8 um by 0.6 um, is encapsulated and has no spores. [1] Petussis has several adhesions, factors and toxins that are responsible for its increased virulence. Pertussis major adhesive is filamentous hemagglutinin or FHA, which can bind to heparin, carbohydrates and integrin CR3 sites. It facilitates increased binding to epithelial, phagocytic cells and extra cellular structures in the respiratory epithelium. There are also the fimbriae which subunits include Fim2 and Fim3 as well as a minor subunit of Fim0 at the tip. Fimbrae infect laryngeal mucosa allowing FHA to colonize the respiratory tract. Two other adhesives are auto transporters pertactin and tracheal colonization factor. These adhesives bind phagocytic cells. Three toxins have been identified and explored. One toxin is Cytotracheal toxin, which is a by-product of peptidoglycan. This toxin is responsible for killing tracheal ciliated cells and prevents the re-growth of respiratory track epithelium. Another toxin of interest is Adenylate cyclase-hemolysis with its multifunction. This toxin attaches to the CR3 of macrophages, invades the cell, promotes apoptosis and creates the synthesis of antibodies. Then there is pertussin toxin. Pertussin toxin consists of five individual subunits. One subunit is responsible for binding to the host cell, thus allowing a second subunit to enter the cell and cause malfunction of the cellular functions. The above mentioned factors are not all inclusive; in fact many others are being further demystified by the genome sequence. [4]

 

[1]

Incidence

Pertussis has a higher occurrence rate in individuals less than five years of age. [4] Health officials are dismayed to report that there has been an increase in pertussis cases since the 1980’s. Increased incidence has been noted in the adult and adolescent populations. The increase in rates may be partially due to a decrease in previously obtained immunity, accurate reporting, changes in vaccine coverage or quality and adaptation of Bordetella pertussis. [2] [3] Another interesting fact about pertussis is that Hispanics are twice as likely as Caucasians to contract the disease. [2]

Transmission

Bordetella pertussis is transmitted by direct contact with the respiratory and or mucus of infected individuals. [3] The bacteria can survive outside the body for several days. [1]The bacteria reside in the throat, nose and mouth. [4] Once the air droplets enter the body they take up residence in the ciliated cells of the respiratory system. [1] It is estimated that 90% of individuals in the same home as an infected person develop pertussis. [3] Pertussis is most contagious during the catarrhal phase. [1]

Diagnosis

Methods of diagnosis for pertussis include cultures, polymerase chain reaction (PCR), nasopharyngeal aspirates (NPA), nasopharyngeal sputum (NPS) specimens and serology. The different methods used to diagnose depend on the age and immune status of patients. In infants cultures are the initial option, closely followed by polymerase chain reaction if no cultures are available. PCR is highly sensitive and faster than cultures but equally high in cost. Cultures are a good method for diagnosis if collected two or three weeks after cough initiated. Nasopharyngeal aspirates are the preferred method for healthcare providers and parents. NPA specimens can be obtained with calcium alginate swabs. NPA and NPS can be obtained with dacron swabs with polystyrene sticks never with cotton wool budded swabs.  Serology tends to be unreliable in infants. PCR and serology are acceptable if patients have not been vaccinated within the last three years. [4] PCR detects Bordetella antibodies. [1] NPS is an appropriate option for adults. NPA and NPS should be sent to lab within four hours. Reagan Lowe transport medium and phosphate buffered saline with 1% calamine acids solution can be used to transport specimens to lab. Upon arrival in lab the specimens can be placed on Reagan Lowe medium, or Bordet Gengou medium with defibrinated sheep or horse blood and incorporating selective and non selective medium.  Bordetella pertussi is capable of growing on BG medium in three to five days. Samples should be incubated times seven days at 35 -36 degrees Celsius prior to being discarded as negative. All above mentioned methods are considered a direct diagnosis. Three methods of indirect diagnosis include agglutinin detection, enzyme linked immunosorbent assay and the Elisa. Agglutinin detection is more available but less sensitive, enzyme linked immunosorbent assay detects antibodies and the Elisa identifies the antitoxin and adhesives. Antibodies can be expected to appear week three and peak between the eight and tenth week. [4] [1]

Signs and Symptoms

The signs and symptoms of pertussis present in four stages, the incubation period, the catarrhal phase, paroxysmal and convalescent phase. [4]

  • The incubation phase last about 9-10 days and is devoid of signs and symptoms. [4]

  • The Catarrhal phase exhibits cold symptoms like a dry non-productive cough, low-grade fever, rhinorrhea. It is highly infectious and lasts between 1-2 weeks. [1] [4]

  • The Paroxysmal stage usually last a minimum of 21 days and a max of 60 days. Patients exhibit an extensive cough with mucous production, emesis and cyanosis. The cough is extended without inhalation concluding with an inspiratory whoop. Paroxysms finalize with the removal of mucus and then are followed by emesis. Other signs and symptoms at this stage include weight loss, leucocytosis, hypoglycemia, lymphocytosis and infrequently encephalopathy. Antibiotics are not effective during this stage.[4] [1]

  •  The convalescent stage lasts about one to three weeks. Patients at this stage have a gradual decrease in cough and return to customary self. [4] [1]

Complications of pertussis are often exhibited by infants and young children. Complications include but are not limited to hypoxia, apnea, seizures, pneumonia, encephalopathy, malnutrition, atelectasis, weight loss, hernias, inanition from repeated emesis and long-term brain damage. [2] [4] [1]

  

Bronchiolar plugging in neonate with pertussis pneumonia. (5)

[1]

Control ,Treatment and Prevention

Treatment for pertussis tends to be strictly supportive. Trimethoprim, sulfamethoxazole and erythromycin are the antibiotics of choice for pertussis. [3] Erythromycin is not given to treat the etiology of the disease but to decrease the infectious period to about five to ten days. [1] Erythromycin is given prophylaxis to household contacts exposed to an infected individual regardless of vaccine history. Close contacts are given prophylaxis antibiotics and observed for fourteen days for symptoms of the disease. [3] Infection with B.pertussis provides certain immunity but humoral antibodies decrease over time. However immunity from having acquired the disease does not necessarily provide protection against the other Bordetella species. [1] The 1950’s and 1960’s saw the introduction of whole-cell killed bacteria vaccines in the fight against pertussis. The above mentioned vaccines have been recently substituted with acellular vaccines. [3] Vaccines are one method of prevention. Five doses of DiptheriaTetanusacellularpertussis (DTAP) are recommended between 2 months and 6 years of age. Dtap is administered at 2, 4 and 6 months of age. A fourth Dtap dose should be administered between 15 and 18 months of age, followed by a fifth Dtap between 4 and 6 years of age. Adults should be vaccinated every 7 to 10 years with Tdap. A single Tdap booster may be given five years after Td. Pregnant women should receive a Tdap postpartum at the hospital or with their primary care provider. [2]

Local Cases

The highest numbers of cases in Texas were reported in Waco, Killen, San Antonio, Bryan, Austin, Dallas/Fort worth, Houston, Amarillo, El Paso and the Rio Grande Valley. [2]

2006 Cases by County [2]

 

Bastrop

 

8

 

Bexar

 

61

 

Burnet

 

8

 

Caldwell

 

4

 

Comal

 

8

 

Dallas

 

80

 

Travis

 

139

 

Williamson

 

109

 
 

Deaths tend to occur in those too young to vaccinate or individuals with a negative history of previous vaccination. [3] In Texas, eight of the nine fatalities reported in 2005 occurred in infants. [2]

Mortality Rates in Texas [2]                                                                       

 

Year

 

Cases

 

Deaths

 

2005

 

2224

 

9

 

2003

 

670

 

5

 

2000

 

327

 

2

 

 

Global Cases

Pertussis is an endemic illness. Epidemics happen every 3-5 years. There are between 5000 to 7000 cases of pertussis reported yearly in the US.  In 2003 there were 13 fatalities reported in the US as a result of pertussis. [3] There were 294 estimated fatalities world wide in 2002. Thirty nine million cases and 297,000 deaths were reported worldwide in 2000. January 8, 2003 saw reports of 115 cases and 17 deaths of pertussis in Northeastern Afghanistan. The 2007 global figures stated 152,535 cases. [4]

References

[1] Medical Microbiology 4th ed. Ed.Samuel Baron, MD. “Bordetella.”  http://www.gsbs.utmb.edu/microbook/ch031.htm   3/7/09

[2] Texas Department of Health. “Pertussis” Last updated August 29, 2005.www.cdc.gov/ncidod/eid/vol7no3_supp/mooi.htm     3/6/09.

[3] Frits R. Mooi, Ingelt M. Van Loo, and Audrey King. Centers for Disease Control and Prevention. “Adaptation of Bordetella Pertussis to vaccination. A case for its Re-emergence” Vol 7. No. 3. Last updated July 2001. www.cdc.gov/ncidod/eid/vol7no3_supp/mooi/htm.  3/6/09.

[4] World Health Organization. “Laboratory Manuel for Diagnosis of Whooping cough caused by Bordetella Pertussis.” Last updated April 14, 2004. http://whqlibdoc.who.int/hq/2004/WHO_IVB_04.14_eng.pdf     3/6/09

(5) Immunizatino Action Coalition. “Pertussis Photos”  http://www.vaccineinformation.org/pertuss/photos.asp  3/18/09