ABSTRACT
Zoonoses present a signicant public health risk as more than 200 zoonotic (bacterial and viral) pathogens have been recognized. Consequently, the World Health Organization is engaged to address the diseases caused by existing and emerging zoonoses. In addition, One Health Initiative has been launched to emphasize that both human and animal health are inextricably linked.1 Zoonotic bacteria have assumed additional importance since more than two-thirds of all emerging pathogens during the last three decades are zoonotic in origin. These pathogens are represented by diverse taxa and are not restricted to any particular class or group of bacteria. Zoonotic pathogens maintain either an ongoing reservoir life cycle in animals or arthropod vectors without maintaining a permanent life cycle in humans, or in some cases, they have jumped the species barrier and then maintain a permanent life cycle in humans and may not need the animal reservoir. Figure 43.1 shows the potential for emerging new zoonotic pathogens as a consequence of increased interactions between humans, pets, and companion animals. These interactions allow species to jump hosts, get adapted, and become opportunistic pathogens. The parasitic vectors and wild animals further aid in the maintenance and spread of potential zoonotic microbial agents. Zoonotic pathogens’ ability to colonize human organs and their disease-causing capability vary considerably. Because these pathogens have evolved to live in multiple hosts including both vertebrates and invertebrates to maintain their enzootic lifestyle, their genomes have evolved to help them sustain life in different host environments. Some of them have a diminished ability to synthesize essential proteins because they can be acquired from the host. However, many of them retain their ability to make specic cofactors and vitamins to sustain efcient growth. These pathogens probably exploit receptors that are common in multiple hosts to colonize and/or gain entry into human hosts. Several groups of pathogens with representatives that can cause zoonotic disease are described in their own chapters in this book. In this chapter, we briey discuss the pathogens of the following zoonotic genera: Anaplasma, Bartonella, Borrelia, Brucella, Coxiella, Francisella, and Pasteurella.
