Six wedges to curing disease

Abstract

Abstract.One of the great challenges in ecology and evolutionary biology is to explain disease, whether caused by infectious agents such as parasites and pathogens, or by the deterioration or transformation of cellular behavior and function, a prime example of the latter being cancer. Decades of observation and research suggest that successfully treating disease requires insights into how the environment mediates the interactions between disease causing agents (DCAs) and diseased individuals. A major finding is that single factor, targeted therapies are not only likely to fail in controlling or eradicating many DCAs, but are also likely to select for resistance, reducing options for subsequent treatment attempts, and in cases of infectious DCAs, rendering therapeutic agents (e.g., antibiotics) obsolete.I argue that meeting the growing challenge of treating disease in agriculture and animal husbandry, in protected and domesticated species, wildlife, and in the human population will require a fundamental understanding of ecological interactions at sites of infection or disease. I discuss different ways in which components of such disease ecosystems mediate DCA and therapeutic dynamics and resistance evolution, and derive a very simple mathematical criterion for therapeutic success. I then touch on how fundamental insights as revealed by the processes of evolutionary rescue and competitive release can help understand why therapies succeed or fail. Finally, I present six "wedges" that can each contribute alone, or as part of multi-pronged approaches to successfully treating disease. The Magic BulletDespite remarkable progress in prevention and treatment, the impacts of diseases in agriculture and animal husbandry, and on protected and domesticated species, wildlife, and human health are likely to intensify into the 21 st century. Humans in particular are increasingly in contact with each other and with wildlife, treated with drug regimens that select for resistance, and adopt life-styles or are exposed to environments that render them more susceptible to infectious diseases and more likely to get cellular diseases such as cancers.For many clinicians the Holy Grail is to discover the Ehrlichian "Magic Bullet"-a drug that will target the disease-causing agents (DCAs) and cure disease. Intuitively, the most effective way to reduce DCAs is to "hit hard and fast". That is, more drug means more kill within the tolerance limits of the patient. Rapid administration of the drug means forestalling further DCA growth and associated symptoms, but also reducing the probability of the appearance of resistant mutant strains. Despite decades of research on pest and disease control (much of it with an ecological basis) this approach and the many alternatives described below remain highly controversial (e.g., [1]).The Magic Bullet may be shortsighted for another reason. What will cure most patients may not be optimal for the general population in which resistant variants may emerge and spread 1 . This problem is in many ways similar...