Whooping Cough

views updated

Whooping Cough

Symptoms and progression of whooping cough

Whooping cough, also known as pertussis, is a highly contagious disease caused by the bacteria Bordatella pertussis. It is characterized by classic paroxysms (spasms) of uncontrollable coughing, followed by a sharp intake of air that creates the characteristic “whoop” of the disease name.

B. pertussis is uniquely a human pathogen, meaning that it neither causes disease in other animals, nor survives in humans without resulting in disease. It exists worldwide as a disease-causing agent, and has caused epidemics cyclically in all locations.

B. pertussis causes its most severe symptoms by attacking specifically those cells in the respiratory tract which have cilia. Cilia are small, hair-like projections that beat constantly, and serve to constantly sweep the respiratory tract clean of such debris as mucus, bacteria, viruses, and dead cells. When B. pertussis interferes with this normal, janitorial function, mucus and cellular debris accumulate and cause constant irritation to the respiratory tract, triggering the cough reflex and increasing further mucus production.

Children under the age of two, particularly infants, are most at risk for serious infection, although the disease can occur at any age. However, once an individual has been exposed to B. pertussis, subsequent exposures result in mild illness similar to the common cold, and thus usually are not identifiable as resulting from B. pertussis.

Symptoms and progression of whooping cough

Whooping cough has four somewhat overlapping stages: incubation, catarrhal stage, paroxysmal stage, and convalescent stage.

An individual usually acquires B. pertussis by inhaling droplets infected with the bacteria, coughed into the air by an individual already suffering from whooping cough symptoms. Incubation is the period of seven to 14 days after exposure to B. pertussis, and during which the bacteria penetrate the lining tissues of the entire respiratory tract.

The catarrhal stage is often mistaken for an exceedingly heavy cold. The patient has teary eyes, sneezing, fatigue, poor appetite, and a runny nose. This stage lasts about 10-14 days.

The paroxysmal stage, lasting two to four weeks, is heralded by the development of the characteristic whooping cough. Spasms of uncontrollable coughing, the “whooping” sound of the sharp inspiration of air, and vomiting are hallmarks of this stage. The whoop is thought to occur due to inflammation and mucous which narrow the breathing tubes, causing the patient to struggle to get air in, and resulting in intense exhaustion. The paroxysms can be caused by over-activity, feeding, crying, or even overhearing someone else cough.

The mucus that is produced during the paroxysmal stage is thicker and more difficult to clear than the waterier mucus of the catarrhal stage, and the person with pertussis becomes increasingly exhausted while attempting to clear the respiratory tract by coughing. Severely ill children may have difficulty maintaining the normal level of oxygen in their systems, and may appear somewhat blue after a paroxysm of coughing due to the low oxygen content in their blood. These children may also suffer from encephalopathy, a swelling and degeneration of the brain which is thought to be caused both by lack of oxygen to the brain during paroxysms, and also by bleeding into the brain caused by increased pressure during coughing. Seizures may result from decreased oxygen to the brain. Some children have such greatly increased abdominal pressure during coughing, that hernias result (hernias are the abnormal protrusion of a loop of intestine through a weaker area of muscle). Another complicating factor during this phase is the development of pneumonia from infection with another bacterial agent, which takes hold due to the person’s weakened condition.

If the person with whooping cough survives the paroxysmal stage, recovery occurs gradually during the convalescent stage, and takes about three to four weeks. Spasms of coughing may continue to occur over a period of months, especially when a patient contracts a cold or any other respiratory infection.

Children who die of pertussis infection usually have one or more of three conditions present: 1) severe pneumonia, perhaps with accompanying encephalopathy; 2) extreme weight loss, weakness, and metabolic abnormalities due to persistent vomiting during paroxysms of coughing; 3) other pre-existing conditions, so that the person is already in a relatively weak, vulnerable state (such conditions may include low birth weight, poor nutrition, infection with the measles virus, presence of other respiratory or gastrointestinal infections or diseases).

Diagnosis

diagnosis based on symptomatology is not particularly accurate, as the catarrhal stage may appear to be a heavy cold, a case of the flu, or bronchitis. Other viruses and tuberculosis infections cause symptoms similar to those found during the paroxysmal stage. The presence of a pertussis-like cough along with an increase of certain specific white blood cells (lymphocytes) is suggestive of B. pertussis infection, although it could occur with other pertussis-like viruses. The most accurate method of diagnosis is to culture (grow on a laboratory plate) the organisms obtained from swabbing mucus out of the nasopharynx (the breathing tube continuous with the nose). B. pertussis can then be identified during microscopic examination of the culture.

Treatment

treatment with the antibiotic erythromycin is helpful only at very early stages of whooping cough: during incubation and early in the catarrhal stage. After the cilia, and the cells bearing those cilia, are damaged, the process cannot be reversed. Such a patient will experience the full progression of whooping cough symptoms, which will only abate when the old, damaged lining cells of the respiratory tract are replaced over time with new, healthy, cilia-bearing cells. However, treatment with erythromycin is still recommended to decrease the likelihood of B. pertussis spreading. In fact, all members of the household in which a patient with whooping cough lives should be treated with erythromycin to prevent spread of B. pertussis throughout the community.

Other treatment is supportive, and includes careful monitoring of fluids, rest in a quiet, dark room to decrease paroxysms, and suctioning of mucus.

Prevention

the mainstay of prevention lies in the mass immunization program which begins in most developed countries when an infant is around two months old. The pertussis vaccine, most often given as one immunization together with diphtheria and tetanus, has greatly reduced the incidence of whooping cough. Unfortunately, there has been some concern about possible serious neurologic side effects from the vaccine itself. This concern led large numbers of parents in England, Japan, and Sweden to avoid immunizing their children in the 1990s, which in turn led to major outbreaks of disease in those countries. Multiple carefully constructed research studies, however, have disproved pertussis vaccine as the cause of neurologic damage. Over 26,000 cases of whooping cough were reported in the U.S. in 2004, continuing a pattern showing an increase in incidence of the disease. This increase is attributed to increased recognition of

KEY TERMS

Cilia —Tiny, hair-like projections from a cell. In the respiratory tract, cilia beat constantly in order to move mucus and debris up and out of the respiratory tree, in order to protect the lung from infection or irritation by foreign bodies.

Encephalopathy —Any abnormality in the structure or function of the brain.

Pathogen —A disease causing agent, such as a bacteria, virus, fungus, etc.

whooping cough in older children and adults, along with physicians who are more often accurately diagnosing and reporting whooping cough in both its classic and milder forms.