Tuesday, May 18, 2010

Is your pussy making you crazy?

Toxoplasmosis — The Bug Rewiring our Brains.

My son’s twenty-something friend is a diagnosed schizophrenic. That’s not to say he is bad or mean or even much of a problem to be around most of the time, but then again, I don’t expect much from him … or most folks in their twenties. A handsome and sweet guy, he is not my first contact with mental illness on life’s meander. I’ve twice had friends commit suicide, and two more played very active roles in their own demises, but my most intimate experience with profound madness was yet closer. When I was but nineteen, my dear and wildly sexy girlfriend had a series of psychotic episodes that resulted in her being involuntarily institutionalized for most of a year, initially at Stanford University Medical Center Hospital, then for a week or so at Santa Clara Valley Medical Center, and finally for many months at El Camino Hospital. I didn’t see her mental implosion coming and it was a very devastating experience. We remained together and very close during those difficult times, but she broke up with me shortly after being released from the hospital. I suspect all these experiences have played a role in my on-going interest in the nature of what we call consensual reality, and how easy it is for any of us to wander too far from life’s safe, well-worn mental path, so when on several occasions in the last few years I stumbled across articles linking schizophrenia and toxoplasmosis, my interest was piqued. Before we look at the linkage, let’s look at the lifecycle of the protozoan parasite called Toxoplasma gondii.

Inside an infected host, the protozoan intracellular parasite Toxoplasma forms cysts five to 50 micrometers in diameter, which are found throughout the host animal, but appear to congregate especially in the amygdala and other brain tissues, as well as in major skeletal muscle tissue, cardio-muscular tissue and the eyes! Wikipedia tells us that Toxoplasma exists in two states, a sexual phase and an asexual phase (tachyzoite). Its sexual reproductive activities only occur when the parasite is inside its primary host, members of the cat family (Felidae), while its asexual phase can occur in any warm-blooded animal or bird. Cats typically get infected after eating a rodent or bird that has been colonized by the parasite in its tachyzoitic phase. Once inside the cat the parasite enters its sexual phase, which culminates in ‘spores,’ called oocysts, which get disseminated via the cat’s feces. These oocysts can exist outside host, for example in the soil, for as long as a year. It is by ingesting these mature oocysts that birds, rodents, and other warm-blooded animals including humans, get infected with Toxoplasma.

The most interesting aspect of this parasite’s behavior is the manner in which it overrides the bird or rodent’s fear of its natural predator, cats, to ensure its own propagation. According to Robert Sapolsky, a professor of biological sciences and neurology at Stanford’s School of Medicine, “…certain parasites control the brain of their host. They hijack our cells, our energy and our lifestyles so they can thrive. Toxo seems to know how to destroy fear and anxiety circuits … a brain region called the amygdala … and toxo knows how to hijack the sexual reward pathway. It takes over sexual arousal circuitry” (Scientific American. “Bugs in the Brain”)

In mice this makes the mouse become sexually aroused by the scent of cat urine. This is the opposite of a successful mating strategy if you’re a mouse, but it’s a very, very successful reproductive strategy for the parasite as it puts the mouse inside the cat quickly. The big question is how does toxoplasmosis affect its other hosts, specifically, but not exclusively humans? This is a particularly important question, as the Center for Disease Control and Prevention estimates that more than 20% of the US population is positive for toxoplasmosis — that’s more than 60,000,000 Americans (CDCToxoplasma gondii Infection in the United States, 1999–2000”). Globally the estimated infection rate per country seems to vary from 35% to more than 80%.

Unfortunately, as an intracellular protozoa (i.e. an organism that inserts itself inside the host’s cells) it is very, very difficult, if not impossible to rid any infected animal of the parasite, and it is also difficult to detect, locate, or isolate Toxoplasma during its latency phase. The good news is that for most humans with healthy immune systems, Toxoplasma appears to be relatively benign.

“Infections rarely cause symptoms, but the parasite remains in the body and can reactivate after lying dormant for years,” according to ScienceDaily (“Toxoplasma Infection Increases Risk of Schizophrenia, Study Suggests”), but more recent research suggests Toxoplasma may play a worrisome role in a host of illnesses, including schizophrenia.

“Toxoplasmosis changes some of the chemical messages in the brain,” says Dr Glenn McConkey of University of Leeds’ Faculty of Biological Sciences. “The parasite infects the brain by forming a cyst within its cells and produces an enzyme called tyrosine hydroxylase, which is needed to make dopamine. Dopamine’s role in mood, sociability, attention, motivation and sleep patterns are well documented … in addition, the ability of the parasite to make dopamine implies a potential link with (schizophrenia and) other neurological conditions such as Parkinson’s Disease, Tourette’s syndrome and attention deficit disorders” (ScienceDaily “Toxoplasmosis Parasite May Trigger Schizophrenia And Bipolar Disorders”).

Robert Yolken, M.D., a neurovirologist at Hopkins Children’s agrees, telling us “findings reveal the strongest association we’ve seen yet between infection with this very common parasite (toxoplasma) and the subsequent development of schizophrenia” (ScienceDailyToxoplasma Infection Increases Risk Of Schizophrenia, Study Suggests”).

Unfortunately, schizophrenia appears not to be curable, per se, at this time. Use of anti-Toxoplasma drugs in conjunction with anti-psychotic drugs have shown some success in ameliorating the disease’s impacts, but schizophrenics, typically suffering from extreme paranoia, are notoriously drug adverse. The disease appears to be lifelong and tremendously expensive with estimates in the US of 300,000 plus victims and costs in the range of $40 billion (Stanley Medical Research Institute. “Toxoplasmosis-Schizophrenia Research”). More promising is a cat vaccine for Toxoplasma (The Medical News “Evidence is mounting to link toxoplasmosis with schizophrenia”).

Also of interest are the proposed cultural impacts of the long association of humans with cats and Toxoplasma. Women with toxoplasmosis show more sexually promiscuous behavior (Wikipedia “Toxoplasmosis”) and men appear to engage more frequently in high risk behavior that can result in violent death (The Edge “A conversation with Robert Sapolsky”).

“Infected men have lower IQs, achieve a lower level of education and have shorter attention spans. They are also more likely to break rules and take risks, be more independent, more anti-social, suspicious, jealous and morose, and are deemed less attractive to women,” Dr. Nicky Boulter, an infectious disease researcher at Sydney University of Technology told Australasian Science magazine . “On the other hand, infected women tend to be more outgoing, friendly, more promiscuous, and are considered more attractive to men compared with non-infected controls.”

I would suggest that these behaviors have high selection value for our species. Females who have sex with multiple partners build additional support alliances for both themselves and their progeny (see Essentials of Physical Anthropology. “Chapter 7”). Men who take high risks typically also tend to have high success rates in reproducing and in acquiring ‘wealth and nourishment’ — better providing for their mates, progeny and community. In the event of the male’s likely death, his offspring are more likely to survive due to his mate’s extra-alliances and the questionable paternity of his offspring. Additionally, culture-wide behaviors may be attributable to Toxoplasma’s ability to alter individual behaviors. In 2006, Kevin Lafferty, a biologist at the University of California, Santa Barbara, made such a claim in his paper, “Can the common brain parasite, Toxoplasma gondii, influence culture?” published by the Proceedings of the Royal Society of London.

“The geographic variation in the latent prevalence of Toxoplasma gondii may explain a substantial proportion of human population differences we see in cultural aspects that relate to ego, money, material possessions, work and rules” we’re told in “Cat Parasite May Affect Cultural Traits In Human Populations” published by ScienceDaily.

“Lafferty’s analysis found that countries with high Toxoplasma prevalence had a higher aggregate neuroticism score, and western nations with high prevalence also scored higher in the ‘neurotic’ cultural dimensions of ‘masculine’ sex roles and uncertainty avoidance” claims Afarensis: Anthropology, Evolution and Science “The Effect of Toxoplasma gondii on Human Culture”.

Could it be that America’s longstanding love affair with military adventurism is a direct result of our pussy loving ways? A doctoral dissertation on that topic could be in my future.


So the question that comes immediately to my mind is “Why cats?” Why not just exterminate them, or at least banish them from human habitations? Sure, they’re fluffy and they purr and folks tend to like stroking them; but I’m allergic to their dander, loath the smell of their excrement (probably my rodent roots), dislike their the fish breath, and frankly I am not fond of their tendency to stick their butts in my face. Gross. But I’m not the key decision-maker in this man-cat relationship. The females of the house get ultimate authority over pets, and there’s the answer: mice. In one of those wonderful synergistic epiphanies I recently recalled also reading science articles linking mice, specifically Mus domesticus, to human breast cancer! Breast cancer is the second leading cause of death of women in the US and the world. According to the American Cancer Society, about 1.3 million women will be diagnosed with breast cancer annually worldwide and about 465,000 will die from the disease. Personally, in the 1970s, I knew five different women who contracted breast cancer in their late-20s to mid-30s, including one very bright woman who succumbed to the disease. Since then I’ve come to know even more women who have suffered from breast cancer. Could the stereotypical fear women allegedly have against rodents be unconsciously based on a real threat?

The idea that some forms of breast cancer could be virally induced is not new. In the 1930s a biologist named John Bittner suggested exactly such a link. The retrovirus known as Mouse Mammal Tumor Virus (MMTV) now has been identified as the culprit, and it is transmissible to humans (Jones, Dan. “Blame the Mouse” New Scientist). What a better way to keep the mouse population down than cats? So thus we have the complete cat-and-rat rationale for modern civilization. The cats keep the girls easy, the boys hyper-active, and breast cancer at bay. That’s what I call intelligent design.

4 Comments:

Anonymous william Earley said...

I remember reading an article about Toxoplasmosis. How the protozoan parasite can attack ones brain. I had a friend that was diagnosed with schizophrenia. We always thought we were talking with two separate people coming from one person. I hear the parasite could be in mice and rat feces. Very interesting writing Mr. Dodsworth! Do post on!
WJE

1:03 PM  
Anonymous Chuck Messenger said...

Incredibly well written and researched, I'm glad you pointed me at it. Maybe you could be a writer when you grow up?

7:35 AM  
Blogger Heidi Milazzo said...

Mouah! I've been looking for a solid reference for this information that I had heard through an unreliable source. I am not sure I would want the cure if I had it.

6:27 PM  
Anonymous Anonymous said...

Mouah! Thank you for the reference. I had heard about this through an unreliable source and am thrilled that it has some scientific clout. I'm also not sure I'd want the anti viral if I had it.

6:29 PM  

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