WHOOPING COUGH Definition Whooping cough is an acute respiratory illness that primarily affects infants and young children. The etiologic agent is usually Bordetella pertussis; occasionally B. parapertussis, and rarely B. bronchiseptica produce a similar syndrome. The descriptive name derives from a distressing, prolonged inspiratory effort that follows paroxysmal coughing. Although both more-morbidity and mortality have markedly declined, whooping cough is still responsible for a significant number of deaths in infants.
The disease was first recorded in the middle of the sixteenth century by Moulton and by DeBaillou. Whether whooping cough was indigenous to Europe or had been transported there in the preceding century is uncertain. Sydenham applied the name “pertussis” to any illness accompanied by violent coughing, but the term became restricted to the epidemic dis-ease that was a well recognized clinical entity by, the middle of the eighteenth century. In 1900 Bordet and Gengou observed coccobacilli in the sputum of a child with whooping cough, but it was not until 1906 that they were able to culture the organism. Many years passed before the Bordet Gengou bacillus was universally accepted as the etiologic agent of whooping cough.
Leslie and Gardner (1931) recognized that B. pertussis underwent marked biologic and morphologic changes on prolonged cultivation, thereby accounting for the difficulties in establishing the etiologic role of the agent and the inconstant protective effect of immunizing preparations. Although the mortality rate whooping cough in the United States began to decline in the early part of this century, the incidence in young children did not significantly decrease until after the use of prophylactic vaccines became widespread 25 years ago. Aetiology. When first isolated, Bordetella pertussis is a minute, nonmotile, poorly staining, gram-negative coccobacillus, 0.5 au. to 1.0 g in length. Capsules can be demonstrated by special procedures, and bipolar metachromatic granules are present.
The complex medium containing blood originally employed by Bordet and Gengou is still often used for cultivation. Primary isolates, phase I organisms, v3i11 not; JIM en conventional laboratory media, but will do so after prolonged passage. At the same time, colonial morphology changes marked pleomorphism of individual cells is evident, and there is an alteration in anti-genic composition. The change from phase I to phase IV has been likened to the smooth to the rough transition of other microbes. The only phase I organisms is virulent, and the only phase I organisms provide effective immunizing material.
Members of the Bordetella genus were formerly regarded as species of Hemophilus. However, the Bordetella group does not have strict requirements for X and V growth factors, and they are antigenically distinct. Although the addition of blood to Bordet Gengou medium is required for the growth of phase I organisms, the blood acts to neutralize bactericidal substances, probably fatty acids, rather than to provide nutrients. Media containing charcoal, starch, or ion exchange re-sins will support the growth of phase I bacteria.B. pertussis produces a heat-stable toxin (endotoxin) and a heat-labile toxin. A role of toxins in the development of disease has not been demonstrated. A hemagglutinin has also been isolated.
The capsular material does not swell in the presence of antiserum. A species agglutinogen has been recognized as well as agglutinating factors that differ between strains. Serotyping is, therefore, a useful epidemiologic tool. The role of the interaction between the organism and phagocytes has not been defined, although the presence of antisera appears to increase uptake of B. pertussis by leukocytes.
Remarkable biologic effects are induced in laboratory animals by the injection of killed phase I organisms. These include the development of heightened sensitivity to histamine and serotonin; in-creased susceptibility to anaphylaxis and to experimental allergic encephalomyelitis; increased antibody production in response to heterologous antigens; and hyperleukocytosis and hypernym phagocytosis. ‘
The factors responsible for these reactions have not been characterized, and the relationship of any of these effects to the primary clinical expression of whooping cough is obscure. It should be emphasized that none of the cel-lular components or products of B. pertussis has been shown to be of central importance in the pathogenesis of whooping cough.