Cats, toxoplasma & madness (again)

There have been a few more recent articles on cats and madness. (Another issue you can trust Opinion Dominion to follow for you.)

This article from the New York Times is mainly a look at research about how toxoplasma gondii spreads and works. It is a pretty weird infection:

Once Toxoplasma enters a host, it spreads quickly. Within hours it can be detected in the heart and other organs. It is even able to infect the brain, which is protected from most pathogens by a tight barrier.

Antonio Barragan ...[was] puzzled at first about how Toxoplasma managed this swift journey.

"When we looked for parasites in the blood, we found very few that were just swimming around," said Barragan, an associate professor. But the scientists observed many of the parasites inside immune cells known as dendritic cells.

Barragan was intrigued. Dendritic cells, common in the gut, often come into contact with pathogens. They respond by crawling to the lymph nodes or the spleen, where they communicate with other immune cells.

"That led us to think, what if this parasite is directing these cells to move and to disseminate through the body?" Barragan said. He and his colleagues put dendritic cells in a dish and injected them with Toxoplasma. They noticed that the parasites triggered a peculiar change: the dendritic cells became hyperactive, crawling for an entire day.

Erk.

Also, as noted on the web in many places, studies indicate that the infection in rats makes them lose their fear of cats. How this happens is very odd:

Scientists at Stanford University recently followed up on these experiments, studying rats and mice. "They actually show a mild attraction to the cat odor," said Ajai Vyas, a Stanford neurobiologist. "It's not just the loss of an old behavior. A new behavior is being induced."

Vyas and his colleagues found that Toxoplasma's effects were precisely aimed at cat odor. The rats were still afraid of dog odor but not of rabbit odor. They could also acquire new fearful responses. "Only the innate fear to the cat was different, which was very surprising," he said.

How Toxoplasma incites this change is a mystery. It is possible that the parasite alters the production of certain neurotransmitters. "But I don't know how some global change could have such a specific effect," Vyas said.

This article is a summary of research going on about schizophrenia and infections, with this comment on studies looking at the possible treatment for toxoplasma (and other infections) for those suffering schizophrenia symptoms:

...we are conducting several double-blind treatment trials that involve the use of adjunctive antibiotics and antiviral medications in persons with schizophrenia and bipolar illness. To date, these medications show some promise in patients with recent-onset disease. The results are less remarkable in persons with long-standing illness. In the future, it might even be possible to develop a vaccine to protect children against possible infections that contribute to these 2 mental illnesses.

Even with what is known today, in clinical settings, some patients who present initially with symptoms suggestive of schizophrenia or bipolar disorder could instead be in the initial stages of viral encephalitis. Some physicians would argue that patients with first-admission psychosis should have a lumbar puncture and CSF analysis, adding other studies as appropriate if indicated by an increase in CSF protein or lymphocytes.

If you feel you are going mad, maybe this should be suggested to your doctor. Just don't mention that you read it on a blog.

Cats and Madness (and the risks of rare steak)

I've mentioned before the possible mind altering effect of toxoplasma, the bug that is carried by cats. (The suggestion being that, just as infected rats have been shown to have a much reduced fear of cats, people with the bug in their brains might also take more risks in life.)

While wandering around the Web this week, I was very surprised to find that there have also been studies to see if there is a link with full blown schziophrenia. See this CDC study here. It's a bit of a worry. The summary:

"Since 1953, a total of 19 studies of T. gondii antibodies in persons with schizophrenia and other severe psychiatric disorders and in controls have been reported; 18 reported a higher percentage of antibodies in the affected persons; in 11 studies the difference was statistically significant. Two other studies found that exposure to cats in childhood was a risk factor for the development of schizophrenia."

I have read before that the rate of toxoplasma infection (as shown by blood studies) varies from country to country a great. France has a very high rate (around 80% !!,) believed to be from a fondness for eating rare meat. So, one would presume if there was any connection between toxoplasma and schziophrenia, it should up in that country's rates of madness. Seems like it does (although the study is very cautious about this):

"Whether any geographic association exists between the prevalence of toxoplasmosis and the prevalence of schizophrenia is unknown. France, which has a high prevalence of Toxoplasma-infected persons, was reported to have first-admission rates for schizophrenia approximately 50% higher than those in England (41). Ireland also has a high rate of Toxoplasma-infected persons in rural areas (42), confirmed by the high rate of infection in hospital personnel in our own study. "

Is there clear evidence that toxoplasma infection can cause schziophrenia like symptoms. Yep:

"Some cases of acute toxoplasmosis in adults are associated with psychiatric symptoms such as delusions and hallucinations. A review of 114 cases of acquired toxoplasmosis noted that “psychiatric disturbances were very frequent” in 24 of the case-patients (10). Case reports describe a 22-year-old woman who exhibited paranoid and bizarre delusions (“she said she had no veins in her arms and legs”), disorganized speech, and flattened affect; a 32-year-old woman who had auditory and visual hallucinations; and a 34-year-old woman who experienced auditory hallucinations and a thought disorder (11). Schizophrenia was first diagnosed in all three patients, but later neurologic symptoms developed, which led to the correct diagnosis of Toxoplasma encephalitis. Psychiatric manifestations of T. gondii are also prominent in immunocompromised persons with AIDS in whom latent infections have become reactivated."

So should cats be seen as a risk factor for schziophrenia? Seems a pretty good case exists:

"Epidemiologically, two studies have reported that adults who have schizophrenia or bipolar disorder had a greater exposure to cats in childhood. In one study, 84 (51%) of the 165 affected versus 65 (38%) of the 165 matched controls had owned a house cat in childhood (p = 0.02) (39). In the other study, 136 (52%) of the 262 affected versus 219 (42%) of the 522 matched controls owned a cat between birth and age 13 (odds ratio 1.53; p <>

Fascinating, hey? And I am very surprised that I had never heard of this before. (The CDC paper is nearly 2 years old now.) Maybe a world wide conspiracy of cat owners is suppressing this news from the MSM.

The parasite of love

Dopamine is key to a parasite’s ability to unite rat and cat, researcher says

Regular readers may well recall that it's been know for some time that rats infected with toxoplasma gondii lose their fear of the smell of cat urine.

What appears new to the story, however, is that the smell of cats not only doesn't worry them, it:

...also makes them mentally and sexually aroused each time their tiny pink noses detect cat smells. ...

"What this damn parasite knows how to do is make cat urine smell sexy to male rats," Sapolsky said. After being exposed in laboratory tests to different cat scents, infected male rats showed a spike in testosterone levels and their testes became engorged.

Not only that, but female rats find infected male rats pretty sexy too:

....female rats also responded to the change in hormone levels by showing preference toward infected males approximately 95 percent of the time, Sapolsky said, which came as another interesting find.

"One of the rules of evolutionary biology is if you're an animal, you don't want to mate with anyone full of parasites," Sapolsky said. "Somehow that doesn't happen with T. gondii infection."

Well then, maybe we are lucky that toxoplasma gondii didn't work out how to make the evolutionary proto-human males of Africa sexually aroused by lions.

(I can see the basis for some good science fiction in this story too.)

The brain infecting parasite returns

Women infected with Toxoplasma gondii have increased risk of attempting suicide: study

This seems particularly bad news about this widespread parasite:

 The study found that women infected with T. gondii were one and a half times more likely to attempt suicide compared to those who were not infected, and the risk seemed to rise with increasing levels of the T. gondii antibodies. Previous mental illness did not appear to significantly alter these findings. The relative risk was even higher for violent suicide attempts. In contrast to the number of women who attempted suicide using any method (517) or violent methods (78), the number of fatalities through suicides in the cohort (18, with eight in Toxoplasma-positive mothers) was still too small to be conclusively analyzed statistically.

The researchers stress that there is more work to be done on the topic, but it stills seem bad news to me.

In other toxoplasma news, I'm sure I read somewhere about work being done in Australia on it.  Yes, here we go

A CAIRNS molecular biologist is working with an international research team to develop a vaccine to prevent cats from infecting humans with a potentially fatal parasite.

James Cook University scientist Rob Walker is focusing his research on Toxoplasma gondii, a parasite that is dangerous to pregnant women because it can cause miscarriage or congenital defects to the unborn child, and can also kill people whose immune systems are weakened.....

Dr Walker, based at the Queensland Tropical Health Alliance at JCU Smithfield, is collaborating with scientists at the University of Zurich and at the National Institute of Health in the US on the pioneer research project.

It is a challenging field of research because scientists cannot replicate, in the lab, the fertilisation process which happens inside the gut of a cat, Dr Walker said.

Dr Walker’s research will focus on how to prevent the cyst-like embryo from forming its protective shell, which may be key to stopping the transmission process. His goal would be to create a vaccine for cats to stop the parasite from being transmitted to humans.

Good luck.

UPDATE:  it's a top week for media discussion of this intriguing brain parasite!   In Slate, it's noted that just as toxoplasma in rats makes them actually kinda like cat pee smell, it might have a bit of a similar effect on people:

In a recent study, Czech scientists gave men and women towels scented with the urine of various animals—horses, lions, hyenas, cats, dogs—which they rated for “pleasantness.” Turns out, men who tested positive for Toxo found the smell of cat urine more pleasant than men without Toxo. For Toxo researchers like me, this was a shock but not entirely surprising. Why? Toxo does approximately the same thing to rats.

 Hmm.  I seem to have missed that til now.  The Slate article is generally about perfumes and their use of animal scents, and it's all of interest.

Toxoplasma meets its match? (And why women should hug their cat)

Newly Developed Anti-malarial Medicine Treats Toxoplasmosis

This sounds quite significant, especially if you own a cat:

A new drug that will soon enter clinical trials for treatment of malaria also appears to be 10 times more effective than the key medicine in the current gold-standard treatment for toxoplasmosis, a disease caused by a related parasite that infects nearly one-third of all humans--more than two billion people worldwide.

Readers may recall that toxoplasma affects the behaviour of rats, making them more available for cat attack, and it is suspected that it may also affect the personality of humans:

Reaction time is affected, with possible implications for automobile accidents and other mishaps. Women seem to become more intelligent, outgoing, conscientious, sexually promiscuous, and kind; changes in men seem to cause opposite trends. All humans tend to be more prone to feelings of guilt (Flegr et al, Lindova et al).

Hey, wait a minute: from a man's perspective, we should encourage women to get this disease! There would be more sex, but more guilt too. Perfect for Catholics then!

But treat men only and it may be the dawning of the Age of Aquarius.

Cat attack on your eyes

New funding for research on parasitic eye disease

People who read about science over the last few years would have heard about toxoplasma gondii (which you can catch from your cat's litter box, amongst other places) and its odd behavioural effects on rats and (possibly) humans.  I don't recall reading about this before, though:

Brooke Anderson-White, PhD, a postdoctoral scholar in pathology, has received a grant from the Knights Templar Eye Foundation Inc. for research to develop vitally needed new treatments for severe eye infections caused by the Toxoplasma gondii parasite.

The parasite infects as many as a billion people worldwide, many of whom have no symptoms. However, it can cause severe problems in those with weakened immune systems or in infants infected during pregnancy, leading to the condition toxoplasmic retinochoroiditis. Infected children can develop severe vision impairment and blindness as a result of retinal scarring caused by the disease. Toxoplasmic retinochoroiditis is a major source of visual impairment in the United States.

It must be small, furry animal news week

Pet rats may harbour deadly fever

There's a warning from an Australian doctor here that some pet rat owners are catching a rare disease from their pets.

It's called "rat bite fever", but as far as I was aware, your "normal" hand raised pet rat pretty rarely bites. (I see from the comments at this site, thought, that it definitely happens.)

Still, the good doctor mentions a case of a Western Australian girl who got an infection but denied having been bitten by her rat. She did clean its cage, though, and perhaps got it that way.

Certainly, good hygiene around pet rats is important, and I would say that rat owners who let them (ugh) lick their teeth (Youtube gives many examples) are simply nuts. But I suspect the danger of a normally clean person catching something from a pet rat is probably no worse than catching toxoplasma from a cat.