Parasite Rex by Carl Zimmer…. aka Why I won’t sleep for a week!

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I’ve always loved being creeped out, and I gravitate to things/animals that most people find revolting – I’ve had pet spiders in the past and I currently have two snakes (Julius Squeezer and Aphrobitey).

So, naturally a book dedicated to parasites was something I wanted to pick up.

It was surprisingly narrative, and he told several stories of his life, some of which pulled on your heart strings. The book opens with a story when he was visiting a hospital full of kids suffering from “sleeping sickness” which can be fatal, and causes extreme duress.

Sleeping sickness is caused by the Tsetse fly which drinks your blood and can leave you infested Trypanosomes. Once the infection reaches your brain the situation becomes desperate – one of the few medicines that will work is 20% arsenic, and its so potent it eats through standard IV tubes, and specialized teflon tubes have to be ordered. The treatment is painful and some patients have to be strapped to their beds.

The book goes into a menagerie of horrors. Theres something called Onchocerca Volvulus aka River Blindess that not only causes you to go blind, but once the worms get into your skin (so mosquitos can get infected and in turn infect others) – people have been known to scratch themselves to death! Fuck.

Up to 60% of certain tribes living along the river over the age of 40 have gone blind.

Here’s a sentence I didnt like reading, “Most human beings have one or more parasites living on them or in them. 1.4 billion people have roundworm. 1 billion have whipworm. 1/3 Europeans are infected with Toxoplasma Gondii which main host is a cat.” Fuck, I have a cat. *glares at Pokey*

Back before we understood what parasites were, scientists and doctors didnt even recognize them as animals, they actually thought that parasites spontaneously arose in the human body as a symptom of an illness, not the cause of the illness itself. The logic being that was that internal organs aren’t exposed to animals or external causes of illness, so how could these things possibly get inside the heart, liver or lungs? They must be byproducts of the body!

A particularily brutal experiment was carried out in Germany (not hitler), where a scientist involuntarily infected convicted inmates with parasites, feeding them meat known to be infected without telling them. After their execution they were dissected and found to have parasites, thus proving that you can contract parasites through digestion, and they werent a byproduct of illness made from the body. Eureka!

Trichinella is a type of worm that you initially ingest through food (mostly). Once the worm infects a cell it divides into a multicelled worm and bursts through the gut wall and into the capilliary system. From there it imbeds itself into the muscle tissue of the host, and turns the surrounding tissue into a softer jelly like substance effectively turning the muscle tissue into a parasite placenta. Revolting. You could theoretically have hundreds of these cysts in your muscle tissue before you start feeling the symptoms. They can even get into your brain.

Trichinella is most commonly found in pork products and this is the strongest case against bacon Ive heard.


Parasites eluded study for a long time not just because the majority are extremely small – but also because of their highly complex life cycles, often requiring 2 or more hosts of different species to complete its cycle. Its not uncommon for a parasite to travel through half a dozen hosts through its life cycle, and often during this life cycle its physical appearance changes. It’s taken decades of research to match adult stage parasites with their larval counterparts.

Along with the different kinds of human parasites this book touches on a ton of different types of animal and plant parasites. I dont know if I wanted to know there are 5 thousand species of tapeworms, but I do now. I also now know that they don’t have any mouths or guts. They absorb their food exclusivly through their skin, which is why they are so flat – maximizing surface area…. they can also grow over 80 ft long. To put that in perspective, thats several school busses long.

While many parasites actually do a good job at not killing the host, and just causing minor inconviences… or castration and mind control…. the battle between catepillars and wasps is brutal and lethal. The pictures included made me squirm. It doesnt help that the author is decent at creating visuals, “she jabs a long hollow dagger through one of the holes, and through it squirts hundreds of eggs”. I think hes doing this on purpose.

This is a very well written book, full of details and experiences the author has gone through. Hes traveled the world from the Amazon, to Africa and both sides of the USA studying parasites and their life cycles.

No background in science is required, this is easily accessible to the general public with very little jargon.


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