Book Review: Riddled with Life by Marlene Zuk

Harcourt.  327 pp., 2007

Subtitle:  Friendly Worms, Ladybug Sex, and the parasites that make us who we are.

Review by Wm Olkowski, PhD

This is a most amazing book, for a combination of reasons.  It is well written, with synoptic summaries of many complex areas pertaining to our health and well being, e.g., evolution, immunology, sexual selection, nutrition, sexually transmitted diseases, disease dynamics, ethnology, and parasite treatment selection, among others.

Did you know that parasites all over the world change the behavior of their hosts so as to aid their own survival and transmission?  Seems logical, right? When one knows that most people in the world are or have been infected with the protozoan parasite, causal agent of Toxoplasmosis (Toxoplasma canis is a parasite of the family cat), the pause for thought about that fact could be significant.  Infections are acquired by breathing cat feces, most likely in changing cat litter.

Infection rates from toxoplasma surveys run from 20-80% of populations assayed.  If such large portions of people have been exposed to this protozoan and if parasites affect the behavior of their hosts we have a cryptic disease-causing organism right in our homes and it could be most severe as it requires an intermediate host, the cat flea.

Cats get the infection from mice and rats that get it from eating fecal matter.  The local sandboxes at playgrounds are good sources too.  T. canis can cause miscarriages, and probably damages the developing fetus.  Now there’s a pleasant thought.  What if these and other organisms are really good at hiding in our bodies causing troubles we cannot detect, nor treat?

Zuk speculates that such hidden parasites are worthy unappreciated threats and could be causes of other modern diseases.  After all, the discovery of how a bacterium, Helicobacter pylori, was the causal agent of stomach ulcers reversed the common belief that stomach ulcers were produced by stress.  Two Australian physicians got a noble prize for this discovery.  A month long course of antibiotic treatment eliminates the symptoms and the infection.   Could these sorts of infections/infestations explain so much stupid and erratic behavior hosts exhibit, including contributing to car accidents and criminal activity, like violent altercations?  Zuk suggests this may be the case, with other extrapolations from animals and even human studies showing higher car accident rates with people infected with Toxoplasmosis.

Alone, the presentation of new scientific findings about our closest “real relatives” on the tree of life is worth attention from all parasitologists, biologists, public health personnel, microbiologists and physicians, just to keep up with new findings.

But Zuk’s thesis is that since these sometimes killers can and have helped our species over the past thousands of years and generations, they may be helpful again now in understanding how we got to be who we are, and how we arrived at our genetic and phenotypical selves and what we could do about it.

Childhood Fevers – Better to Leave Them Untreated

Her discussion about fevers is exemplary for new information, and its consequences for health care and treatment selections.  For example, childhood fever is the most common reason parents bring children to hospital ERs, all for nothing, it turns out.  Also, such visits are the most common cause for visits to the ER overall.  Think of the economic cost and the pain and suffering one experiences in the ER, waiting, and waiting, for help in the midst of a crowd of really sick people.  Then, add in the costs of buying the aspirin, acetaminophen, ibuprofen, to treat such fevers, to say nothing about the side effects these drugs can have.

New information says that treating a childhood fever is useless.  This comes from a paper in the Bulletin of the World Health Organization that surveyed the use of fever reducing drugs and their efficacy in a number of countries.  This conclusion was based on large populations in double-blind placebo controlled studies.  They found that these drugs made no difference in outcome, neither in duration nor comfort level of the children.  Febrile seizures are also another example of misinformation.

Pathogenicity Is A Gradient

Our life as humans is riddled with many other organisms, particularly potential and actual pathogens like helminths, protozoa, bacteria, prions, insects, rickettsia, and viruses.   But more importantly what these species have done to our species needs further examination.  A pathogen in the strict sense is any organism that can cause disease.  Zuk presents a view of pathogens as being our partners in evolution, and through this appreciation she thinks we can learn a great deal about how to get along with them.

Maybe.  At least in a grand view not just focus on eliminating them.  As she demonstrates over and over we are still learning a great deal about most of these species.  {There aren’t any I would tolerate deliberately tolerate, however, maybe I would make an exception for good strains of probiotics, including Escherica coli, toxic strains of which invade at birth and can track along for a lifetime causing problems).

Zuk’s goal in presenting a great set of findings about poorly studied species of great medical importance.  I use that term in the sense that my grandmother stressed to me: “When you lose your health, you lose everything.” And these organisms can destroy bodies and lifetimes.

The ignorance about these organisms is widespread, their biology and control is poorly understood and difficult to diagnose by medical professionals, and mostly overlooked by everybody else.

Inventory the Parasites of the World

This is an example one of the ideas Zuk sprinkles here and there through out the book.  This one is dear to me as I started evaluating this idea back in graduate school.  I found out that this process was already on going.  Now we have the tree of life web project ( by E.O. Wilson.  The objective is to document all the life forms on the planet, making it a sort of wikiLife project.  This maybe just the time for this sort of thing because it relies on volunteers, mostly.

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