Messinaxs.awardspace.info Review:Azithromycin and sinusitis - Azithromycin and sinusitis Azithromycin and sinusitis
Country: Europe, DE, Germany
City: Kiel, Schleswig-Holstein
I love this calendar! It is an inspiration to see members of the animal kingdom coexisting peacefully and, in fact, truly enjoying their amazing friendships with other species. Makes me feel humans could do the same if we tried harder. Each new month has its own inspirational story and photo. There is a companion book with the same title detailing additional unlikely animal friendships which I love to keep on hand and give as gifts to someone, say, in the hospital or a shut-in who loves animals.
Carl Zimmer, author of Parasite Rex, writes with all the authority of a practicing parasitologist, despite the fact that he is actually a science journalist. In addition, and invaluably, his account is heavily informed by his deep understanding of the processes and mechanisms of natural selection. Evaluating Parasite Rex purely as a knowledge-delivery device, it is simply not subject to criticism.
But the book is so much more than that. Zimmer is a very Stephen King of pop science, by which I do not mean to damn him with faint praise; Parasite Rex kept this reader on the edge of his seat, in an agony of suspense and terror, for the weekend it took to devour it from cover to cover. Zimmer knows what he is doing.
The first sections of the book relate a series of parasite life histories, examples of the complex, delicately-balanced, highly-specialized strategies modern parasitic organisms have evolved. The organizing principle behind these stories is clear, and it isn't based on the taxonomies, strategies, or environments of either parasites or hosts -- Zimmer has selected these particular accounts, and the order in which he relates them, in order to bring the reader efficiently to a crescendo of visceral horror.
Most people tend to experience a strong reaction of disgust and aversion when presented with information about parasites; apparently we cannot help but empathize with an infested host, and to sympathize accordingly. Zimmer lays the examples on so thick, each more horrifying than the last, that reading his book becomes a sort of intellectual equivalent of hunkering down in a war zone.
My own particular favorite is the parasite Sacculina carcini, which makes its home inside a crab. It begins by sterilizing its host if it is female, and if the host is male, both sterilizing it and forcing it to produce hormones that render it behaviorally female. It then begins to infiltrate and replace the crab's body, including much of its brain. The crab continues seeking food, which it feeds directly to its parasite. When Sacculina reproduces, it places its offspring in a pouch where the crab's offspring would go (if the host is male, the parasite forms a pouch in the appropriate location). The crab acts to protect the parasite's offspring just as it would its own -- and even carefully disperses them when it is time to do so, just as it would carriers of its own genetic heritage. This is the stuff of science fiction, a parasite that takes over everything and leaves only its host's outer shell intact.
Nevertheless, it is perhaps still more horrifying to learn that many parasites of vertebrate hosts have evolved to produce (or cause their hosts to produce) neurotransmitters that tend to create behavior patterns that serve the parasite's interests far more than the host's. For example, if a parasite lives in a fish in one stage of its life cycle, but wants to be in a bird for the next, it makes its piscine host less afraid of shadows on the water, and more interested in feeding near the surface. Indeed, psychologists have found distinct behavior patterns -- different in males and females -- associated with being a human host to cysts of the parasite Toxoplasma. Toxoplasma wants its host to be eaten by a predator, so it makes males tend to be loners who resent authority, and makes females tend to be outgoing and overly-trusting. By the way, if, like me, you grew up with cats, you almost certainly host Toxoplasma yourself.
Having shattered his audience with such ghastly memes as these, Zimmer next begins to put some of the pieces back together. He mitigates the naked horror of the first chapters with an exploration of the role parasites and parasitism have played in the evolution of multi-cellular organisms. To a degree he overstates his case; if it is true that parasites are a third and in many ways causal factor in the well-known phenomenon whereby wolves cull the weak out of the caribou herd, it is not accurate to claim that the parasites are "the" drivers of evolution. It is, however, accurate to say that parasites co-evolved with both caribou and wolf, and that the role parasites generally have played in all natural selection has been consistently and systematically over-looked and under-considered in the evolution literature.
There is much of interest in the evolution section which I will not discuss here; rather I will confine myself to the final punchline: since medical science has begun successfully eradicating many kinds of parasites from the post-industrial human experience, new disorders have begun to emerge to replace the "missing" organisms.
Many parasites have the ability to reduce their hosts' immune responses. If the presence of such parasites was, on average, an evolutionary constant, then we can expect humans to have evolved immune systems that operate optimally only when the chemicals these parasites produce are present. Remove the parasites and the human immune system becomes too strong for its own good, and begins treating harmless material as pathogenic (consider the epidemic of allergies in post-industrial countries versus the nonexistence of allergies in the third world) or begins attacking its own body (i.e., newly-developed bowel ailments such as Crohn's disease or irritable bowel syndrome).
The reader is obliged in the end to adjust to life with the relatively abstract and alloyed horror induced by the knowledge that we in principle should not seek to eliminate parasites from the human experience. We might engineer them, subvert them to serve our interests just as they have done to us for millennia, but we ought not to eliminate them. Every gardener knows that it is clearing an area of its naturally-balanced flora that creates an opportunity for hyper-infestation of weed species; let's hope medical science doesn't continue forcing us to learn the same lesson with our own bodies.