Episode available within Canada only.

We like to believe we’re in control. But if what we’re discovering about parasites is anything to go by, who is really in control is a lot more complicated, and a lot more interesting, than we ever imagined.

So let “The Nature of Things with David Suzuki” help you get over the ick factor, and explore the world of parasites.

Scientists have collected hundreds of examples of parasites that brainwash their hosts.  And now researchers are starting to untangle these parasites’ evolutionary tricks of the trade.  

In the coastal estuaries of California, Professor Kevin Lafferty of the United States Geological Survey introduces us to a flatworm that lives in three hosts - a snail, a fish and a bird. This parasite’s influence is so profound that it tips the balance of the local ecosystem. Lafferty found that parasitized fish are 10 to 30 times more likely to be eaten by birds.

Photo Credit: David Huges

In the rainforest of Brazil, we hunt for the elusive zombie ant with Penn State entomologist David Hughes. These insects get brainwashed by a seemingly simple fungus and ordered to turn against their queen and colony.

And just wait until Professor Joanne Webster of London’s Imperial College reveals “feline fatal attraction”. That’s when toxoplasma gondii, a single-celled parasite, convinces a rat that it’s actually sexually attracted to the smell of cat urine. This makes the rodent easy pickings for its most dangerous predator. And all so the parasite gets to move into the cat, where it can reproduce and complete its lifecycle.

But guess what -- human adults can be infected by toxoplasma too.  And when the parasite is inside us it doesn’t know it’s not on board a rodent and it tries the same mind manipulating tricks.  Jaroslav Flegr of Prague’s Charles University has linked toxoplasma infections in humans with increased traffic accident rates and even personality changes. Kevin Lafferty also studies toxoplasma, and he thinks explains some of the differences between different human cultures.

Dalhousie University’s Dr. Shelley Adamo likes to call parasites nature’s neurobiologists.   And in a world where we could always use better treatments for mental disorders like depression, Dr. Adamao says perhaps mind controlling parasites can provide some answers for us. 

Credits (Click to expand)


Annette Bradford

associate producer
Robert Ballantyne
Olena Sullivan


directed, produced and written by     
Mike Downie

David Wells

Jacques Milette

Michael Sweeney
Ed Middleton

additional cinematography
Nigel Kinnings
Lukáš Materna
Karel Man

location sound
Gabe Chu
Andy Paddon-Smith
Pedro Rodrigues
Mary Wong
Tomas Ksir
Jon Goodman

local producers / fixers
Denise Fuzer
Ivan Zbiral

sound design
Alan Geldart

graphic design
Terry O'Neill
Vinit Menon
Titus Hora
Mark Sylvain

visual research
Gina Cali

Eric Barnett

music consultant
Patrick Russell
online editing
Edwin Wilkinson

re-recording mix
Ron Searles

associate director
Renée Moreau
resource coordinators
Analisa Amoroso
Megan Beeckmans

unit manager
June Hall
senior manager
Documentary Unit
Wilma Alexander

production manager
David Wilson
senior producers
FM Morrison
Caroline Underwood

executive producer
The Nature of Things
Sue Dando
executive director
Documentary Programming
Mark Starowicz
special thanks
Adamo Lab, Dalhousie University
Charles University
Dr. Harry Evans
Hughes Lab, Penn State University
Imperial College, School of Medicine
Alejandra Jaramillo
Maya Kaushik
Raquel Loreto
Marine Science Institute, UCSB
Dr. Rick Maziels
Penn State Film Office
Lauren Quevillon
Brian Sewell
Jenny Shaw
Kelly Weinersmith

additional images   

Discovery Access
Science Photo Library
Tony Fracasso
CBC Archives
David Barlow Photography
Pioneer Productions
Aquavision TV Productions
Shutterstock Footage
Alex Wild/Visuals Unlimited, Inc.
"Toto le Némato" de Yves Elie - © VB Films 2007 Images J.L Fauquier
Stanley E. Malcolm, Ph.D.
Dave Pressland/FLPA / Science Source
Kelly Weinersmith
David Hughes
US Fish & Wildlife Service, National Digital Library
World War Z (Paramount Pictures) 
Night of the Living Dead (George A. Romero)

produced with the participation of

CMF Image

The Nature of Things
with David Suzuki

produced by
Canadian Broadcasting Corporation


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