DR NICKY BOULTER: It's ingenious, you know? Nothing else can live in so many different organisms and survive.
JAROSLAV FLEGR: No drug for this exists.
DR BOULTER: It's the ultimate survivalist, the locust of parasites.
FLEUR RISTIC: The hardest bit was saying goodbye to her.
BELLA GANKO: I could lose the vision of both my eyes and that's scary.
STEVE RISTIC: This thing exists, it's out there, we're surrounded by it.
DR BOULTER: 2.5 billion people worldwide. 8 million Australians. Quite an amazing little beast.
ALEX CULLEN: The "little beast" has a long name - Toxoplasma gondii. Toxo for short, it's spread by cats, passed on to us. The consequences on the unborn, the young and the weak can be devastating.
RHONDA: I no longer had a happy, healthy, beautiful baby. I had a very sick baby.
ALEX: So nothing can kill it?
DR BOULTER: No.
ALEX: Toxo is the perfect predator.
DR BOULTER: Predominately, it goes to your muscle and your brain and eyes quite often as well, so anywhere basically that it can sit and evade the immune system.
ALEX: Dr Nicky Boulter has a cat called Sox and has spent her career studying toxo. It's unique among deadly parasites because it has the ability to infect every warm-blooded animal on Earth.
DR BOULTER: It makes it the ultimate parasite, if you like, to be able to infect any warm-blooded living creature.
ALEX: But here's the extraordinary thing - it can only breed inside one animal. It lays eggs inside the gut of a cat. When they are excreted in droppings, they can survive in soil or sand for up to 1.5 years.
DR BOULTER: Then when somebody comes along, either a human or any other animal, touches that soil or the sand, then you'll have eggs on your hand. You'll scratch your nose or clean your fingernails and you'll then become infected.
ALEX: Infection takes between 3 and 10 seconds. Toxo spreads through the bloodstream, taking refuge in eyes, muscles and brain tissue — building cysts to thwart the body's defences.
DR BOULTER: They encase themselves in this cyst wall, which is impervious to any immune attack. To have something sitting in little cysts in your brain, it's kind of freaky, it's like something out of 'X-Files'. You expect them to burst out and "Eee!" any moment now.
ALEX: In healthy adults, symptoms often present as flu or a lack of energy. But toxo becomes really dangerous in pregnant women where it's passed by mother to unborn child.
FLEUR: I knew about toxoplasmosis, you know, very briefly about not changing cat litter.
ALEX: Fleur and Steve Ristic from Perth have a beautiful daughter, Indigo.
FLEUR: Do you want me to lift you up?
ALEX: They were expecting their second child when three months ago, Fleur discovered she and her unborn baby had been infected. Can you even think when or how you would've?
FLEUR: I go back on everything. I go back to playing with Indigo in the sand.
STEVE: And, you know, it was a daily occurrence. We were always in parks with sandpits and she's always fossicking around. I mean, was largely oblivious. I had no idea that Toxoplasmosis existed and the sort of precautions we ought to be taking to avoid it and certainly that there was any possibility for us to be testing for it because it's just not routinely done in Australia.
ALEX: In France and other parts of the world, pregnant women are routinely tested for toxo and so are sandpits where children play. Fleur was not tested so at first thought her second pregnancy was fine.
FLEUR: About 18 weeks, started feeling her move and kick and a few weeks later, Steve said, you could feel her kicking from my - really starting to connect.
ALEX: Her 20-week ultrasound was fine but some time in the next two weeks, Fleur and her unborn baby caught toxo. Because Fleur didn't know, because there are no routine tests, she wasn't given the drugs that could have protected her daughter. Her little girl was delivered stillborn. Fleur was able to hold her and give her a name - Harmony.
FLEUR: To be honest, the hardest bit was saying goodbye to her for the last time. That was... knowing she wasn't with me anymore once we left the hospital. We left without our baby. Of course it was always in the back of my mind, there's what-ifs. What if I'd had a blood test at that 20-week ultrasound and that's probably around the time when I caught it.
ALEX: Who made this?
BELLA: I did.
ALEX: No, you didn't! (LAUGHS) Bella Ganko is living proof of the importance of timely diagnosis. 17 years ago, her mum, Rhonda, caught toxo. She most likely got it at a Christmas party in the 27th week of her pregnancy.
RHONDA: It was basically a cocktail party, so hors d'oeuvres were served.
ALEX: Among the hors d'oeuvres — a slice of kangaroo carpaccio - uncooked meat is prime real estate for the parasite. The kangaroo would have been infected by toxo in cat droppings.
RHONDA: That one bite of food potentially will affect my child for the rest of her life. She did smile initially but she stopped smiling. And at some point I went and looked in my baby development book and somewhere in there discovered that blind babies do smile initially but then stop because they don't see.
ALEX: Rhonda took her to her doctor for an examination.
RHONDA: He handed the baby back to meand said, "Yes, you are right, Rhonda, she can't see and I think she has a condition called Toxoplasmosis and have you ever heard of that before?"
ALEX: Toxo is a leading cause of blindness worldwide but Bella's parents and doctor took quick action. 12 months of intensive treatment with antibiotics halted the attack.
DR: Just going to have a look at the back of your eyes now, Bella.
ALEX: Bella's sight returned to her right eye, the left is permanently scarred. The parasites are still in her eye and could break out again.
BELLA: I don't know what's going to happen in the future. I could lose both the vision of both my eyes and that's scary. Not knowing is scary.
ALEX: What's also frightening is what's now emerging about how toxo might be affecting our minds and influencing our behaviour. It was the discovery that infected rats curiously become attracted to cats that sparked scientific interest.
DR BOULTER: They actually become attracted to the smell of cats and it's believed that it's the parasite affecting the behaviour of the rat in this manner to try and take it back to the cat,
be eaten and therefore finish its life cycle, complete its life cycle.
ALEX: The change in behaviour in rats led scientists to ask could toxo also change us? Here in the heart of Prague is one of Europe's oldest universities. Charles University - more than 650 years old - and it's here for the past 20 years, one man's life has been consumed by Toxoplasmosis. Biology professor Jaroslav Flegr is an eccentric character... So Professor, Albert Einstein studied here?
PROFESSOR: Yes. Just here in this building.
ALEX: ..but he's recognised as a world authority on toxo. His studies over 22 years on more than 13,000 people reveal unusual behaviour among those with toxo. Toxoplasmosis can make women promiscuous?
PROFESSOR: Yes. (CHUCKLES)
ALEX: Men with Toxoplasmosis are more than two times more likely to have a car accident?
ALEX: Men with Toxoplasmosis more likely to have a lower IQ?
PROFESSOR: More likely.
ALEX: Women with Toxoplasmosis spend more money...on clothes?
ALEX: (LAUGHS) You're very quick there! Men with Toxoplasmosis are more likely to be suspicious and jealous?
ALEX: Professor Flegr theorises that while toxo often lies dormant, when it breaks out, it can interfere with those parts of the brain that control how we behave. You're convinced a lot of psychiatric diseases are caused by parasites.
PROFESSOR: Yes, yes, I think so.
ALEX: While not all academics agree, one of his findings is getting plenty of support — the link between cats, toxo and schizophrenia. Evidence dates back to the 1890s when a rise in the popularity of cat shows coincided with a surge in schizophrenia cases. Professor Flegr is convinced.
PROFESSOR: Very large fraction of schizophrenia is triggered, is caused, by Toxoplasma infection.
DR BOULTER: People born in cities where there's generally a greater number of cats have a higher instance of schizophrenia. People that have had cats during their childhood, there's a link that people have higher levels of schizophrenia there. Also places where there are very few cats, such as the highlands of Papua New Guinea, there's virtually no toxoplasmosis and virtually no schizophrenia.
ALEX: There's no doubt that cats are behind the spread of toxo but no-one's suggesting for a minute that cats should carry the blame.
DR BOULTER: There's always the paranoia about cats and cleaning out the litter tray but I think very few people actually know about the fact that you can catch it from meat, so eating uncooked meat,
gardening and not wearing gloves or not washing your hands thoroughly. I think the knowledge on that is very poor.
STEVE RISTIC: It's a simple test, it's a simple blood test so it is extraordinary to believe that it's not at least made available or given the option to people to say, "Look this thing does exist
and you can be tested for it."
FLEUR: I want to try and get it out there so it doesn't happen to other people.
ALEX: You don't want other people to go through what...
FLEUR: No. it's been hell on earth.
ALEX: Do you want everyone to know? Do you want the message to get out there to stop this happening again?
ALEX: How important's that, do you think?
BELLA: So important. I mean, if they just knew what caused it and how to prevent it, it could stop other people getting the same thing as me. Just a little information that could help save so many people.