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Dr. Rieux resolved to compile this chronicle…

to state quite simply what we learn

in a time of pestilence: that there are more things

to admire in men than to despise.

—Albert Camus: The Plague

Many bacterial, rickettsial, and viral diseases are classified as zoonoses because they are acquired by humans either directly or indirectly from animals. This chapter considers bacteria causing four zoonotic infections that are not covered in other chapters. All four species, Brucella abortus, Yersinia pestis, Francisella tularensis, and Pasteurella multocida, are Gram-negative bacilli that are primarily animal pathogens. The diseases they cause, brucellosis, plague, tularemia, and pasteurellosis, are now rare in humans and develop only after unique animal contact. The full range of zoonoses considered in this and other chapters is shown in Table 36–1.

TABLE 36–1Some Important Bacterial Zoonotic Infections



Brucella species are small, coccobacillary, Gram-negative rods that morphologically resemble Haemophilus and Bordetella. They are nonmotile, non–acid-fast, and non–spore-forming. The cells have a typical Gram-negative structure, and the outer membrane contains proteins. The genus Brucella contains nine closely related variants that differ primarily in their preferred terrestrial or marine hosts. Taxonomists vacillate as to whether they should be called species or something else. The three most commonly infecting humans, B abortus (cattle), B melitensis (sheep, goats), and B suis (swine), will all be referred to here as Brucella abortus or simply Brucella...

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