A genus of gram-negative bacteria which are coccobacilli and obligate aerobes, and fail to ferment carbohydrates. These bacteria are respiratory pathogens. Bordetella pertussis, B. parapertussis, and B. bronchiseptica share greater than 90% of their deoxyribonucleic acid (DNA) sequences and would not warrant separate species designations except that the distinctions are useful for clinical purposes. Bordetella pertussis is an obligate human pathogen and is the causative agent of whooping cough (pertussis). Bordetella parapertussis causes a milder form of disease in humans and also causes respiratory infections in sheep. Bordetella bronchiseptica has the broadest host range, causing disease in many mammalian species, but kennel cough in dogs and atrophic rhinitis, in which infected piglets develop deformed nasal passages, have the biggest economic impact. Bordetella avium is more distantly related to the other species. A pathogen of birds, it is of major economic importance to the poultry industry.