Whooping Cough 2

Whooping Cough
Bordetella pertussis
Contents

Symptoms and Diagnosis of Whooping Cough

Mechanisms of transmission and the infection process

Strategies for prevention and treatment

Description of Bordetella pertussis

Bordetella pertussis is a small, gram negative coccobacillus. Grown in culture, it has complex nutritional requirements. It is non-motile and it produces a 105 kDa toxin, Pertussis toxin, similar to the cholera toxin.

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Symptoms and Diagnosis of whooping cough

Whooping Cough still exists worldwide:

Whooping cough, the disease caused by Bordetella pertussis, is a serious respiratory disease primarily afflicting young children. The bacteria colonize the trachea and the bronchial tubes of the infected person. In severe cases whooping cough can lead to pneumonia and even death. Although a vaccine against the organism is available, the disease still exists throughout the world and there have been several small epidemics of whooping cough in recent years.

Whooping Cough occurs in two stages:

The first stage symptoms resemble those of a common cold, sneezing, runny nose and coughing. During this stage, the infected person is most contagious, but is seldom diagnosed. This stage lasts for one to two weeks.

The second stage is characterized by severe coughing episodes. These episodes consist of many rapid coughs in succession, followed by a "whoop" sound and then a quick inhalation. Often the face and lips of the infected person turn blue during these coughing fits as a result of oxygen deprivation. Other symptoms include excessive mucus production and vomiting. Occasionally, edema, hemorrhages and vascular plugs develop in the brain, leading to neurological damage. It is during this second stage that most diagnosis occurs. This stage lasts for four to six weeks.

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Mechanisms of Transmission and the Infection Process

Transmission

Aerosol: Bordetella pertussis is transmitted from infected persons via air-borne droplets produced by sneezing and/or coughing.

Direct contact: Bordetella pertussis is also transmitted through direct contact with infected persons.

Infection Process

Bordetella pertussis colonizes the respiratory mucosa between the mouth and the nose, and the beginning of the lungs.

Bordetella pertussis binds preferentially to ciliated cells in the respiratory mucosa.

Bordetella pertussis produces a number of adhesins which aid in its ability to colonize. These include Filamentous hemaglutinen (Fha), Pertussis toxin (Ptx), Pili (Fim 2, Fim 3) and Pertactin.

Bordetella pertussis produces only localized infections. Nonetheless, some symptoms suggestive of a systemic infection are evident as the toxins produced by B.p. are released by the colonizing bacteria.

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Virulence attributes of Bordetella pertussis

Adherence

Bordetella pertussis is successful at colonizing the ciliated cells of the respiratory mucosa by producing several adhesins. Taken in combination, they provide varied strategies by which Bordetella pertussis is able to adhere to the host tissue. Both filamentoug hemagglutinin (Fha) and Pertussis toxin (ptx) bind to glycolipids found primarily in ciliated cells. In addition, Ptx also binds to phagocytic cells, thus promoting phagocytosis. The role of pili and pertactin, two other adhesins produced by Bordetella pertussis, is unclear.; Toxins
Toxin production by Bordetella pertussis. is crucial to its virulence. Bordetella pertussis produces four known toxins, three of which play important roles in virulence. Pertussis toxin (Ptx) is an A-B toxin similar to that produced by Vibrio cholera. In addition to aiding in adherence, Ptx causes deregulation of the host cell’s adenylate cyclase activity. This leads to increased cAMP in host cells, which in turn leads to a variety of metabolic changes which are detrimental to the cell. Bordetella pertussis also produces an invasive adenylate cyclase independently, which then produces high cAMP levels in the host cells it invades. Another toxin, tracheal cytotoxin, is responsible for killing ciliated cells.

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Strategies for prevention and treatment of whooping cough

Prevention

Prevention of whooping cough is best realized by vaccination against Bordetella pertussis. The recommended vaccination schedule is for infants to receive inoculations at 2, 4 and 6 months, and then again at 15 months. This is to be followed by a booster at 4 to 6 years. The dead cell vaccine used for many years caused unpleasant side effects in approximately 20% of inoculated infants. This lead to the development of a new vaccine made with purified proteins. Although the rate of side effects is considerably reduced in the new acellular vaccine, it has also been shown to be less effective against Bordetella pertussis. Therefore, the current recommendation is for the whole cell vaccine to be used for the initial three inoculations and for the acellular vaccine to be used for the two subsequent inoculations.

Treatment

Antibiotic treatment for whooping cough is effective if the therapy is started during the first stage of the disease. Since diagnosis seldom occurs during this time, antibiotic therapy is usually ineffective at decreasing the length of the illness. However, antibiotics are given to children to decrease infectiousness and thereby help prevent transmission of the bacteria to uninfected persons. In severe cases of the disease, hospitalization becomes necessary.

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Links to related sites

http://www.hawaii.gov/doh/resource/comm_dis/cddpertu.htm What is Pertussis?

http://www.vdh.state.va.us/epi/pertf.htm What is Pertussis?

http://www.slackinc.com/general/iche/stor1298/saw.htm Detection of Bordatella in hospital air

http://www.uhl.uiowa.edu/Publications/Hotline/1997_11/update.html Detection of Bordatella by PCR

http://www.cdc.gov/nip/vacsafe/vaccinesafety/publications/lancet.htm Impact of Anti-Vaccine Movements on Pertussis Control

http://www.cdc.gov/nip/Q&A/genqa/pert.htm Pertussis (Whooping Cough) Q and A

http://www.cdc.gov/nip/media/moneyrep.htm Consumer Q and A about Pertussis vaccine

http://www.drreddy.com/shots/whoop.html Pediatricians view of whooping cough

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Last Revised: February 22, 1999