Pertussis: Nursing

Pertussis, also known as whooping cough, is an acute respiratory infection caused by the bacteria Bordetella pertussis. The disease is characterized by paroxysmal cough, meaning fits of sudden and periodic cough, as well as abundant respiratory secretions. It can affect people of all ages, but it can be particularly severe, and even life threatening in children younger than 6 months.

Now, the respiratory tract consists of the upper and lower airways, as well as the lungs. The tiniest branches of the lower airways, called the bronchioles, end with the alveolar sacs, which are lined by a thin membrane that allows gas exchange to occur.

Now, the respiratory system is equipped with defense mechanisms against potential pathogens. For example, the upper and lower airways are lined with ciliated epithelial cells that sweep pathogens that make their way inside, to be expelled back out through the nose or mouth. At the same time, the lungs have plenty of immune cells, like macrophages, that react when a pathogen makes its way in by producing cytokines that attract more immune cells. These immune cells destroy and dispose of the invading pathogen.

Okay, now, pertussis is an infection caused by a gram-negative bacillus, called Bordetella pertussis. Risk factors for acquiring infection include pregnancy, close contact with an infected individual and lack of immunization or underimmunization.

Pathology-wise, pertussis is transmitted by airborne contagious droplets. After inhalation, the bacteria adheres to the epithelial cells of the upper respiratory tract and the nasopharynx. Once attached, it produces toxins that damage the local tissues, causing inflammation and edema of the respiratory tract. This results in abundant secretions of the respiratory tract. In addition, some of the toxins can also paralyze the cilia, thus preventing the bacteria and the mucus secretion from being cleared. All this mucus irritates the trachea, causing fits of violent coughing.

Furthermore, some toxins will also increase the blood vessels sensitivity to histamine, a cytokine released by immune cells during an infection. This makes the blood vessels leakier, allowing fluid to move out into the surrounding tissues, causing edema in the airway. So the swelling can obstruct air flow, causing shortness of breath, and it also causes the characteristic “whooping” sound when they try to take a deep breath.

Some complications of pertussis include secondary infections, like pneumonia and otitis media, as well as hypoxia and apnea when the physiology of gas exchange is affected. In rare cases, these complications, particularly hypoxia and secondary infections, can cause CNS complications of their own, like encephalopathy and seizures.

Now, the clinical manifestations of pertussis occur following an incubation period of around 7 to 10 days. Then, the disease progresses in three stages. The first stage, called the catarrhal phase, lasts 1 to 2 weeks, and manifests as a mild upper respiratory tract infection with mild or no fever, rhinorrhea, malaise and a mild nonproductive cough. The second stage, called the paroxysmal stage, is characterized by paroxysms of cough, which are severe, forceful and repeated coughs that occur during a single expiration. These bouts are often followed by a prolonged inspiration that produces a characteristic “whoop” sound.

The third and the last stage, called the convalescent phase, is characterized by a residual cough that lasts 2 to 3 weeks.

Diagnosis of pertussis starts with the client’s history and physical assessment. A complete blood count can show leukocytosis and lymphocytosis. The causative bacteria can be identified in nasopharyngeal cultures or with a PCR from nasopharyngeal secretions. Alternatively, the antibodies against Bordetella pertussis can be identified using serology testing.

Treatment of pertussis is focused on treating the bacterial infection with antibiotics and providing respiratory support. The antibiotic of choice is usually a macrolide like erythromycin or azithromycin, or trimethoprim/sulfamethoxazole for those who can’t take macrolides.