Parasite Rex, by Carl Zimmer, looks at the role parasites play in the game of life. Starting with the history of parasitology, and moving through the prevalence and treatment of different parasite-related diseases, Zimmer opened my eyes to how much of the world is dependent on parasites.Along the way I learned lots of interesting stuff, such as the fact that chimpanzees self-medicate. I knew they use tools and hunt in packs, but never realised that not only do they eat unusual foods to help fight infections, but that they seem to be able to determine what it is that is causing a particular set of symptoms and eat the appropriate leaves or bark which contains the chemicals to fight off the parasites.Zimmer also discusses issues such as introducing parasites to control pest species, using the example of the parasitic wasp which keeps the population of cassava mealybugs in check. When the bugs, natives of South America, made it to Africa, they devastated the cassava crop until the relevant wasp was introduced.One of the most interesting ideas is that the presence of parasites is an entirely natural occurence throughout the spectrum of life, and can actually be a good thing, citing the example of Crohn’s disease which originally started as a disease exclusive to rich, New York Jews back in the 1930s. It turned out that rich New Yorkers had been amongst the first to be cleared of tapeworms as public health systems took effect, and that deliberately re-infecting sufferer’s of Crohn’s disease with tapeworms from animals (which therefore wouldn’t themselves cause a disease) cured them of Crohn’s in 80+% of cases.This is definitely a book which will give you a whole different perspective on the world.