Re-Emerging Zoonotic Bacterial Diseases
Leslie Garry Adams
Abstract
We are constantly in a co-evolutionary arms race with the microbes that inhabit us, the ultimate aim being co-adaptation, i.e. the microbe develops means of survival and the host develops factors for resistance. Long ago Pasteur observed, 'the microbes will endure,' thus it not surprising that infections and their consequences continue to plague individuals and populations. This is especially true, because they not only out number us so much, but adapt more easily, reproduce more quickly, and are genetically enormously more resilient and diverse. The pathogens have evolved genetically to enable crossing of anatomic and cellular barriers, evading host resistance mechanisms, and establishing competition-free niches rich in nutrients, thus facilitating entry, survival and proliferation to disturb cellular functions and cause disease. Indeed, the majority of the world's population will not survive long enough to die of ageing processes due to microbes, yet we share with them the same necessity to survive. Most zoonotic transfers usually don't work, because for the pathogen to move from one host to another usually requires tens or hundreds of bacterial genes to orchestrate the many subtle adaptations necessary for surviving in the new host. Death of the host is rarely to the advantage of the pathogen and rather indicates lost of equilibrium between the host and the pathogen (Lederberg, 1998). Zoonotic bacterial pathogens are those microbes transmissible from animals to man and capable of adapting and causing clinical disease, and as a result survival of the complete host-pathogen living system may be compromised with severe acute and chronic disease manifestations and death frequently being the outcome of this encounter (Lindsay, 1997). These emerging diseases are usually the ones that capture our attention first