Imagine you are at a cocktail party.
Some sort of creative kickstarter’s big reveal that includes an in-house DJ — some forty-year old guy named Craig with a receding hairline and reflective aviator glasses— set up in the corner next to some fiddle leaf fig plant. You clutch in your grip a cocktail that gives bourbon a bad name; some new spin on an Old Fashioned that’s replaced the bitters with wood smoke and orange peel with Rosemary twigs. In the corner, opposite Craig the DJ, there is a twenty-something in a three-piece suit with far too much pomade in his hair and the vague, nauseating smell of sandalwood.
There is cat hair on his collar.
“Hello,” He reaches out his hand “I’m Chad, entrepreneur”. He tells you with distilled enthusiasm and large white teeth. As you shake Chad’s hand and hold unblinking eye contact you come to the realization that staring back at you, through the echoing dot of his pupil is not Chad at all, but a gaping, dark abyss where Chad once resided.
Down inside the deep structures of his brain the parasite Toxoplasma Gondii sits on his intracellular throne with his parasitic fingers wrapped around the marionette strings used to control Chad’s corporal, entrepreneurial form
T.Gondii is really the business visionary here— the master mind— and Chad is merely the necessary meat sack for the mission. The vehicle of success and venture.
Except, this absurd Twilight Zone sequence can’t possibly be the reality of things. Can it?
The Scoop on T. Gondii in the news
A recent news story (HERE) thrusted the parasite front page and center, once again. It seems that every few months, Toxoplasma Gondii (Or T. Gondii to his friends. Also known as Toxo to those in his closest circle.) rears its head in popular science articles. This particular article told the tale of a sample of individuals who appeared to be both infected with T. Gondii and possessed the tendency to engage in business endeavors.
According to the article those that tested positive for exposure to T. Gondi were between 1.4 and 1.7 times more likely to go into business or entrepreneurship of some capacity.
The theory behind all this is that T. Gondii infections result in the human host being more likely to engage in risk taking behaviour. And since calculated risks are what being an entrepreneur is all about, it was speculated that Toxo gave these particular individuals a competitive edge.
Along with shaky business ventures, T. gondii has been theorized to have an hand in the greater frequencies of car accidents and incidences of unbridled behaviour that appear to pop up in those afflicted with the parasite This behavioural manipulation eventually pushes out into the periphery to include episodes of psychosis and even more complicated neuropsychiatirc disorders such as Schizophrenia.
It has been speculated that it may even be the culprit behind “crazy cat ladies” — the rare incidences where women hoard dozens of cats. Unusual behaviour that is neatly packaged into the guise of a mind controlling parasite that is seemingly driven by its reproductive cycle.
Something which can only be completed inside the body of a feline.
Do the three cats that I cohabitate with put me at risk for cat induced psychosis? Doubtful. They may put me at risk for enlarged lymph nodes, lethargy and the classic “flu-like” symptoms of the miscellaneous microbial infection. If I am really unlucky and/or immunocompromised, I could end up with a case of a brain abscess or some lovely collections of tissue cysts.
For all appearances, T. gondii’s mind control powers seem to be highly exaggerated in regard to human behaviour.
But, for curiosity sake, where does one begin to point accusatory fingers at this protozoa that happily hijacks the nervous system?
It all starts with a dopamine hypothesis.
T. Gondii’s entrepreneurial bent and promiscuity
Several papers have noted that T. Gondii may hijack the central nervous system by increasing dopamine production. Dopamine is our feel good neurotransmitter that is a heavy player of the pleasure pathway. It is released in sexual arousal and substance use — just to name a few stimulating and pleasurable events. Dopamine can be considered our reward for engaging in specific behaviours that elicit the release of the neurotransmitter. We feel GREAT and will seek out ways to engage in more dopamine release.
Sex, drugs and rock n roll. We will go to great lengths to achieve a little hit of dopamine.
It is possible that an increase in risk taking behaviour could result from an increase in the activity of dopaminergic neurons, specifically of the ventral tegmental area of the brain— the apparent center of our reward pathway. If our risky behaviour is rewarded by domaine release then we would likely engage in these behaviours more frequently in order to achieve that same pleasurable release.
The VTA has a hand in controlling motivation, orgasm and addiction. This area of the brain is also involved in some emotional cross-talking with the amygdala and other areas of the limbic system. When it comes to rewards and gains, we humans generally go out on a limb. We will often take a risk in fulfilling these cravings.
All for that dopamine hit.
Toxoplasma gondii has been found to encode genes for the synthesis of tyrosine hydroxylase, an enzyme involved in the catabolism (or break down) of amino acid tyrosine into L-DOPA. L-DOPA is then further broken down into dopamine, along with several other neurotransmitters. Theoretically, the presence of T. Gondii, inside a host’s brain could muck around with the level of catecholamines, such as a marked increase in dopamine. This, in turn, could lead to behavioural changes.
An Esquire article form 2007 (HERE) used incidences of female promiscuity as a particularly eyebrow raising example of the effects of T. Gondii’s chemistry hijacking.
Rest assured, if you have an insatiable sexual appetite for carnal pleasures, chances are you are not being controlled by a protozoan parasite. You can blame media and the rats for that interpretation.
And as we explore further, it all seems to come back to the rats.
Free will and Eukaryotic mind control
While the debate of T. Gondii’s ability to muck about in our brain and navigate our behaviour is still on going, it appears that it does a fairly good job of controlling rodents.
It has been observed that rodents with a Toxo infection will suddenly lose their fear based aversion to cat urine. In fact, they appear to almost be aroused by the smell and are drawn, hopelessly, to the deadly cat.
Haven’t we all experienced that misguided sexual attraction? The sting of unrequited love with the wrong person? Helplessly drawn to them despite all logic and reason.
Dopamine. It’s a hella of a drug.
In this case, the rat’s behaviour appears to have a role in nature’s ultimate desire for procreation and gene propagation. Our friend T. Gondii can only reproduce inside the intestines of a feline. It must get back into the cat to continue its genetic lineage. All this to go forth and feast upon the brains of the unwilling for it’s day-to-day activities. As an obligate intracellular parasite, T. gondii needs mammalian cellular machinery to carry out its metabolic functions.
The fastest way to get into the intestine of a cat is through a tasty rodent treat.
It appears that T. Gondii hijacks the rat’s sexual arousal pathways in order to lure the rat to the cat. By stripping the rat of it’s natural aversion to the scent of cat it can position the rat close enough to complete its cycle. This type of behaviour manipulation is what originally sparked the theories of T. Gondii induced behavioral changes in humans.
All working through pleasure-reward systems and dopamine.
One can see why it may be thought to contribute to some neuropsychiatric behaviours.
Let’s take Schizophrenia, the popular example.
Schizophrenia is a neuropsychiatric disorder characterized by increased dopamine levels and an array pf positive and negative symptoms. These include: hallucinations and delusions (positive) to the very eerie waxy catatonia (negative). There has been speculation that when our friend T. Gondii is not making women more promiscuous or involved in an innovative start up, it is wreaking havoc in the brains of those with Schizophrenia.
Where does all this come from? Well, there appears to be a correlation between seropositive individuals (those testing positive for the parasite) and a Schizophrenia diagnosis.
Here you have a parasite that can manipulate dopamine levels and you also have a disorder that is characterized by the increase of dopamine. Easy to put two and two together, right? But it’s not that simple. Not all seropositive individuals have Schizophrenia and not all people with a Schizophrenia diagnosis are seropositive. There appears to be no causation here, meaning the cause of schizophrenia is likely not Toxoplasma Gondii.
And that’s where things can become confusing for media reports and the general population digesting the information.
Just because something exists along side something else does not mean that they have any effect or influence on each other. If there is no evidence to link the two —nothing describing influence, symbiosis or a connection — then you can not assume that they have any cause and effect relationship. Just because A is found in the presence of B does not mean that A created B or vice versa.
We like things to be neat and we possess the tendency to see patterns. Tidy explanations and seemingly causal events make us feel good (dopamine, again?) because it ties up loose ends. We come to a conclusion in a straight line and feel confident about the knowledge. In one glance we can see where all the puzzle pieces fit — all displayed for us to digest in a satisfying horizon line.
When things get complicated and messy, as most things in nature do, we tend to get a little agitated and anxious by all the busy, tangles before us.
T.Gondii is a good example of our misunderstanding of correlation and causation.
Is T. Gondii making you more entrepreneurial and a high-risk client for insurance companies? Is it the reason the older gentleman down the street from me smells like cat urine and has upwards of 10 feline friends? Is it the reason for your cousin’s schizophrenia diagnosis and paranoid delusions?
While we can’t say for certain, it appears that it is unlikely. The evidence just isn’t quite there.
Does T. Gondii affect rat behaviour in a way that is evolutionarily favourable for the parasite? Well, yes, there is evidence that appears to suggest this.
The thing is, you can’t just jump from rats to humans. What’s good (or in this case, bad) for the rat is not good (or bad) for the human and vise versa. We just can’t extrapolate from a rodent model to a human model.
What’s to be learned from all this?
Cook your meat well, wash your hands after changing the litter box, correlation does not equal causation and just because it’s proven in a tiny rodent does not mean it’s going to perform the same inside the complicated biological system in the meat sack that is you.
Science is messy. It intersects and it turns in on itself. It expands beyond what we can observe in one quick glance.
We have to search for the answers. We have to keep asking questions.