“Despite all our efforts, the parasites still have the upper hand. The question is: Do we have to sit there and take it like all the other hapless host species on our planet? Or can we use our ingenuity and creativity to find ways of taking advantage of their molecular survival tactics?”—Dickson Despommier
In the following excerpt from the preface to People, Parasites, and Plowshares: Learning From Our Body’s Most Terrifying Invaders, Dickson D. Despommier argues that despite all the misery they bring, we have much to learn from parasites:
Hollywood has picked up on the parasite theme from time to time. Alien is one of my all-time favorite examples of this. Everyone who has seen it remembers the showstopper: it comes early on in the film, when the “embryo” of the beast, in a torrent of blood and guts, bursts right out of the chest of John Hurt, then slithers off and raises havoc with the crew of that hapless spaceship. No matter how many times I’ve seen it, that “birthing” scene always freaks me out. But that was science fiction, and with some obvious inconsistencies in the parasitic life cycle, I might add. Trust me, the lives of real parasites are far more riveting.
Ever since we became a species, some 200,000 years ago, parasites have been responsible for untold amounts of human suffering and countless deaths. For instance, some experts believe that Homo sapiens almost became extinct as the result of epidemics caused by malaria that coincided with a time when our numbers were perhaps as low as 400,000 individuals. The worst part is that this killer is still with us. In just over the past one hundred years, as many people have died from malaria worldwide as now live in the United States. While the number of people dying from this one parasite is high, consider the fact that malaria in all its forms (there are four) infects some two billion individuals each year. This reduces the mortality rate to around 1 percent, making this group of infectious agents some of the most successful parasites on the planet. There are other evolutionary winners out there, too. For example, the number of humans currently infected with intestinal helminths (worms) is also in the billions. Tragically, what this really means is that there are a lot of people harboring more than one parasite….
Despite all our efforts, the parasites still have the upper hand. The question is: Do we have to sit there and take it like all the other hapless host species on our planet? Or can we use our ingenuity and creativity to find ways of taking advantage of their molecular survival tactics? That is one of the main themes of this book. I am aware of many pieces of half-finished research on parasites that, if developed further, could benefit our species in some totally unexpected ways: breakthrough treatments of those suffering from type 1 diabetes, for example, or the successful transplantation of organs obtained from nonhuman animal sources, such as pigs. I also highlight the amazing ways in which these body snatchers succeed in carrying out their complex lives at our expense.
Much of the information I have drawn on reflects the new biology of the twenty-first century. Ever since the advent of the first crude microscopes, popularized by Antonie van Leeuwenhoek in Holland and Robert Hooke in England, we have become obsessed with knowing in every detail how parasites and all the other life forms on our planet carry out their lives. Over the past one hundred years of research in the life sciences, the complexities of biological networks and systems have become accepted paradigms for defining the ways life sustains and thrives in an ever-changing, often hostile environment. The closer we are able look at any living organism, the more we are drawn to understanding its complexities. We want to know it all. Today, science has provided researchers with a plethora of tools that they have then used to probe the inner workings of the cell, often without disturbing it. Florescent-labeled compounds that target just one aspect of its intracellular environment, coupled with sophisticated, high-power, computer-assisted microscopes give unprecedented resolution of cellular structures and their functions. The ease of sequencing entire genomes in just days has opened the door to a new world of investigation at the molecular level and will continue to offer exciting opportunities for a global understanding of the process of parasitism. Genetically manipulating organisms—inserting, altering, or even removing specific genes—in which the expression of individual molecules can be studied at will has helped to redefine what is and what is not essential for things such as infectivity, host range, metabolism, suppression of the immune responses, and site selection once they enter an animal. Many of the stories chronicled in this book could not have been written even five years ago, but owing to the rapid advance of cutting-edge technologies, parasitologists around the world are publishing heaps of new information that has altered forever our view of the host-parasite relationship. Hopefully, they will receive adequate levels of financial support to continue their work. All that having been said, at the molecular level, we are just beginning to appreciate how much we still need to know before we can say we really understand any given biological entity, be it host or parasite.
I hope that by the time readers come to the end of my book, they will have a new respect for an often misunderstood form of life and will also realize that if we ever succeed in eliminating parasites from our environment, we will still need to study their lives in the laboratory in order to be able to apply their strategies for survival to our own world.