This science document is a quick read chock full of interesting biologic data and the role of many small creatures in the struggle for survival on earth. The writing is scholarly but not difficult to follow and the line drawing of lifecycles was very helpful as was the appended guide to those lifecycles. I wish they had been available to me in my boring microbiology classes in 1967.
One good quote among many: “Parasites have a special problem since their survival depends not only on their own adaptations, but also those of its host. Choose a host on its way to extinction and that could be the end of the parasite.”
I never cease to be amazed by the complexity and adaptations of various life forms, and never more so than with the intricate changes they go through in the struggle to survive. I was aware of many of these genera, having seen one or two patients with liver flukes,(trematodes) amoebic liver abscesses, toxoplasmosis, hydatid cysts, and schistosomiasis and other patients with intestinal tapeworms, hookworms, pinworms, ascariasis, and giardiasis. But my favourite true story of parasite adaptation is a flatworm that when cut in two both, survive and remember how to navigate a maze they have been trained on. And as cannibals the memory of the eaten shows up in the consumer! Toxoplasma gondii only reproduce in the intestine of cats but they get there by making rats and mice lose their fear of cats and run up to the felines to befriend them. There is other documentation of parasites altering the the behaviour of their onboard hosts to ensure their survival although neither of these phenomena are mentioned here. The nasty spirochete Borellia burgdorfii makes its way from deer via black-legged ticks to humans, including me. But that is a fatal one way route to extinction for this Lyme disease bug as it must be almost impossible to get back to deer via the ticks. As an aside, it seems to me that Covid19 thrives because, unlike it’s cousin SARS, it kills only a small percentage of its human hosts. SARS was too lethal for its proliferation, at least in humans.
The Nebraskan pocket gopher seems to take the prize for hosting the most parasites, most of them neither harming nor helping the host, but the small South American rodent tuco-tucos may challenge them for that prize. And the northern migration, because of climate warming, of Trypanosoma cruzi, the cause of Chaga’s disease that has killed millions of South Americans is cause for concern. It has now reached the middle of the United States.
Scientists and especially biologists everywhere will enjoy this very informative book but is probably too technical and loaded with unpronounceable Latin species names for many others.
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Thanks, The New Yorker.
The Passionate Reader 