Whooping Cough is the disease generally recognized as being produced by the bacterium Bordetella pertussis. Bordetella is a genus consisting of Gram-negative rod-shaped aerobic cocci that also includes B. bronchiseptica and B. parapertussis. Both occasionally are isolated from whooping cough patients, but are not the primary cause. The structure of the organism is similar to that of H. influenzae, but differs in that it is a strict aerobe and does not require specific blood components for growth. Plus, it will grow in various types of growth media.
B. pertussis is transmitted in airborne droplets expelled from an infected person’s respiratory tract. After the bacterium is inhaled, it selectively attaches itself to epithelial cells in the respiratory tract, where it produces a toxin that invades the lining of the throat, windpipe, and bronchial tubes. The resulting tissue damage causes a very thick and irritating mucus to be produced, causing spasms of coughing with the characteristic “whoop.”
After an incubation period of about ten days, signs of an infection begin to appear – runny nose, sneezing, and coughing. This first stage (prodrome) lasts about a week or two before the episodes of uncontrollable coughing. Each episode (paraxysm) may consist of five to twentyrapid coughs, with the patient unable to breathe in between. At the end of these episodes, there is a forced inspiration of air, causing the “whooping” sound. Prolonged coughing episodes can lead to anoxia (decreased oxygen in the blood), expelling of mucus, and vomiting. The second stage can last for one to six weeks, or longer, with the third stage of convalescence lasting several more weeks.
Various toxins produced by B. pertussis are thought to induce the accumulation of mucus, destruction of the tracheal cilia, and the extensive coughing. Since the central nervous system is involved, it contributes both to the morbidity as well as the mortality associated with the disease. There is also the risk of secondary infections, involving the weakened respiratory tract, particularly in young children. Out of the forty million cases, it may produce 400,000 deaths. There is no antibiotic that is completely successful, but erythromycin or trimethoprim-sulfamethoxazole seem to be the most effective.
Contrary to popular belief, deaths from whooping cough declined a full decade before the invention of the vaccine in the 1940s. Today, a killed pertussis vaccine is given in combination with tetanus and diphtheria toxoids as the DPT vaccination. The vaccine can produce serious side effects, including high fever, convulsions, brain dmage, and death. In 1988, the US government began a compensation plan for children injured from the vaccine ($80 million worth). Since then, the National Institute of Health has been in the process of developing a safer vaccine. An alternative to the DPT vaccine is an acellular vaccine known as ADPT.