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Understanding Pertussis

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If you are anything like me, understanding immunizations and the disease processes they help prevent can be very confusing. In my coming articles I would like to review these diseases individually.

With a growing number of parents choosing not to immunize their children, it has become increasingly important for practitioners to have a firm understanding of these disease processes. It is vital for clinicians to recognize and provide education to patients and family regarding the risks associated with not vaccinating.

So, today let’s focus on Pertussis, which is also widely known as “whooping cough”.

Microbiology and Epidemiology: Pertussis is noted to cause significant respiratory complications and illness. The Center for Disease Control and Prevention (CDC) has noted that

B. pertussis is the most poorly controlled bacterial vaccine-preventable disease in the U.S.”

The causative agent is Bordetella pertussis. It is a gram-negative coccobacillus pathogen. While there are other species within this pathogen “family” that could also cause pertussis, this is labeled as being the most common culprit.  It is highly contagious and is noted by UpToDate as being potentially fatal, especially in children and infants.

Transmission and Incubation: As noted above, pertussis is highly contagious and is transmitted primarily through aerosolized respiratory droplets. From the time that a person is initially exposed to the pathogen, incubation is generally seven to ten days, but could be as long as three weeks or more.

The pathogen attaches itself to the cilia which line the upper respiratory tract and the nasopharynx. Once adhered, the organism causes damage to surrounding respiratory tissue, which may be what contributes to the development of the whooping-like cough.

Clinical Presentation: The clinical presentation for pertussis and its severity can be quite variable, depending on factors such as age and the strength of immunity to the organism. Symptoms are more commonly noted in children and infants than in adolescents and adults. The table below discusses the three stages for classical pertussis.

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Diagnosis: The CDC provides a detailed description of the clinical criteria for diagnosis of pertussis. They require that cases either be confirmed via positive laboratory findings or by exposure to a laboratory confirmed case of pertussis AND a cough must be present for a minimum of 2 weeks with at least one of the following clinical symptoms:

  • Paroxysms of coughing,
  • Inspiratory whoop,
  • Post-tussive vomiting or
  • Apnea with or without cyanosis (if less than a year old)

So, with this information, the question now is, what lab do I obtain with a patient suspected to have pertussis?? 

Well, initially obtaining a culture of nasopharyngeal secretions from the posterior nasopharynx is recommended by the CDC. The test itself is highly specific and proper technique in obtaining specimen is very important to increase sensitivity. If the specimen is obtained within the first two weeks of symptoms, sensitivity is at its highest.

The second test that the CDC recommends is the Polymerase Chain Reaction (PCR) which is also done on nasopharyngeal secretions and is obtained in the same manner as the culture. The benefit of doing this test is that it has higher sensitivity and results are available sooner (one to two days). Like the culture, results are more sensitive if obtained within the first two weeks of symptom onset.

Other tests to consider would be a CBC to evaluate for elevated WBCs, direct fluorescent antibody testing, or even serology testing if symptom onset is between two to eight weeks. While these tests are options, the direct fluorescent antibody test and serology testing are not recommended to be done routinely when trying to confirm diagnosis.

Differentials:  If a patient has a cough, that doesn’t automatically mean they have pertussis. There are other diagnoses to keep in mind as you are asking questions and working up the patient.

A few of the many possibilities include upper respiratory infection (URI), community-acquired pneumonia (CAP), or even respiratory syncytial virus (RSV). The question is, how do you attempt to differentiate between these diagnoses and that of whooping cough??

Ok, for starters, with a URI you are not going to have the whooping type cough that is associated with pertussis.

If pneumonia is a consideration… look for other symptoms such as a fever, productive cough or crackles on auscultation. Also, a CXR may show signs of an infiltrate, suggestive of pneumonia. In contrast, pertussis will generally have normal CXR findings.

Lastly, RSV… look for other symptoms such as wheezing, dyspnea and accessory muscle use, sinus/ear involvement, or history of prematurity in infants.

By grouping together your positive findings, this can help guide you on your next intervention…such as whether the patient needs lab work, imaging, etc.

Treatment:  Ok…. So let’s assume we have a confirmed diagnosis of pertussis, what should we put our patient on….??? Well, the first thing that you need to consider is their age… this will help guide your medication choice.

The below table summarizes treatment options according to Epocrates. While antibiotic use will help eradicate the infection (most effectively if started within 3 weeks of symptom onset), it may do little to help decrease coughing symptoms. Symptoms may be so severe for some patients that they require hospitalization.

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Patient/Parent education: The CDC website provides a great deal of information regarding home management of pertussis. Let’s take a look at some of their recommendations….

  • First off, while it would seem obvious to recommend taking cough medicine to help ease coughing related to pertussis, it is not recommended, especially in children under the age of 4.
  • Remind patients to complete all antibiotics as prescribed
  • Create an irritant free environment from items such as cigarette smoke or dust
  • Use of a humidifier may help break up mucus secretions
  • Practice good handwashing
  • Drink plenty of fluids to avoid dehydration and eat frequent small meals to help reduce vomiting

OK….so this article covered a lot of information, I hope this helps clarify things a bit and makes pertussis a little easier to digest.

Tracy Lindstrom RN, BSN, DNP-S

References:

CDC (2014). Pertussis/Whooping cough (Bordetella pertussis) 2014 case definition. Obtained from http://wwwn.cdc.gov/nndss/conditions/pertussis/case-definition/2014/

CDC. (2015). Pertussis (Whooping cough). Diagnosis and treatment. Obtained from http://www.cdc.gov.proxy.wichita.edu/pertussis/about/diagnosis-treatment.html

Cornia, P., Lipsky, B. (2015). Bordetella pertussis infection: Epidemiology, microbiology, and pathogenesis. UpToDate. Obtained from http://www.uptodate.com.proxy.wichita.edu/contents/bordetella-pertussis-infection-epidemiology-microbiology-and-pathogenesis?source=search_result&search=pertussis&selectedTitle=5~150#H269764

Cotter PA, Miller JF. Bordetella. In: Principles of bacterial pathogenesis, Groisman EA. (Ed), Academic Press, Ltd, London 2001. p.619.

Kline, J., Lewis, W., Smith, E., Tracy, L., Moerschel, S. (2013). Pertussis: A reemerging infection. American Family Physician. 88(8). 507-514

Lutfiyya, N., Sharkey-Asner, C., Faye-Lund, A., Leung, A. (2015). Pertussis. Epocrates App

Matto, S., Cherry, J., Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies. Clinical Microbiology Review. 18(2). 326-382.

Menzies, S., Kadwad, V., Pawloski, L, et al. (2009). Pertussis assay working group. Development and analytical validation of an immunoassay for quantifying serum anti-pertussis toxin antibodies resulting from Bordetella pertussis infection. Clinical Vaccine Immunology 16(12). 1781-1788

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Tracy Lindstrom
Tracy Lindstrom has been a registered nurse for 10 years with experience working in ICU, Home Health, and Case Management. She is currently working on completing her Doctorate in Nursing Practice at Wichita State University (Go Shox!!), with plans to work in family practice after graduation, focusing on underserved populations. She enjoys spending time with her husband, three beautiful daughters and 2 dogs.