Caution, cat lovers? Toxoplasmosis & suicide

[Ronja]

I think I have read about this somewhere else (maybe Google+), but I did not have time to look into the claims before now.

To summarize: Being infected with Toxoplasma gondii (T.gondii), a parasite of domesticated cats, may be connected to suicide attempts in humans. Until 2009 only pregnant women were actively warned to avoid cat poop, because a T. gondii infection in a fetus typically causes pretty severe brain damage and even blindness. However, already in the mid-nineties, there was some interest for whether T. gondii could affect the behavior of humans, and some links to socially undesirable behavior were found [1,2]. During the last three years, some studies have indicated that showing antibodies for T.gondii is associated with a history of suicide attempts and, in those attempting suicide, a greater number of attempts. The original find was published by Arling et al. in 2009, in Journal of Nervous and Mental Disease [3].

Background: Toxoplasma gondii (T.gondii) is a parasite that infects about one-third of the world's human population. Typically 20-80 % of any human population is infected [2]. If the human host has a normal immune system and response, T. gondii stays in relative passivity in the brain and muscles of the host, often encased in small cysts. It has been known since at least 1994 [4] that T. gondii changes the behavior or mice and rats to "suicidal", i.e. the infected rodent gives up its normal neophobic behavior (fear/avoidance new things) and thus also stops avoiding cats, with easily predictable results [5]. This rodent behavior gives T. gondii access to its main host, the domesticated cat. In developed countries, humans can get infected when handling cat poop, e.g. when emptying litter boxes, from unwashed or badly washed vegetables, undercooked meat or contaminated kitchen utensils or drinking water.

First report: According to the Arling et al. (a team lead by T. Teodor) article "Although preliminary and bearing replication, this is the first report, to our knowledge, of an association between attempting suicide and T. gondii." so the possible toxoplasmosis - human suicide link was first announced in 2009.

Some later reports: In 2010 a study was published that found "In a sample of 20 European nations, the prevalence of the brain parasite Toxoplasma gondii [in the population] was positively associated with national suicide rates for men and women. [6] Also in 2010, a study of a Turkish sample of less than 400 people found that "The sero-positivity level for anti-Toxoplasma IgG antibodies among suicide attempts (41%) was significantly higher than the control group (28%)." [7] The Teodor group published a second and third study in 2011. One was on women specifically, and it found that the suicide-inducing effect of toxoplasmosis appears to be especially strong in the elderly, i.e. the length of the time that the person has been infected could play a role. [8] The other was on German patients with schizophrenia (sample size 950), and found that the correlation between T. gondii antibodies and suicidal behavior was strong in younger patients but insignificant in older ones. [9]

The NHS analysis of another study (from Denmark) summarizes in a calming tone [10]:

Conclusion

Cat owners need not fear today’s news, but pregnant women and people with impaired immunity do need to continue to exercise sensible precautions...

Sources:

[1] http://journals.cambridge.org/action/di ... id=4198580
[2] http://schizophreniabulletin.oxfordjour ... 3/757.full
[3] http://journals.lww.com/jonmd/Abstract/ ... _of.6.aspx
[4] http://journals.cambridge.org/action/di ... id=4262084
[5] http://rspb.royalsocietypublishing.org/ ... 1591.short
[6] http://www.amsciepub.com/doi/abs/10.246 ... .107.5.424
[7] http://www.sciencedirect.com/science/ar ... 3810000769
[8] http://journals.lww.com/jonmd/Abstract/ ... tes.3.aspx
[9] http://www.sciencedirect.com/science/ar ... 6411004373
[10] http://www.nhs.uk/news/2012/07July/Page ... -risk.aspx

[Audley Strange]

I've been harping on about this for quite a few years (about 2005 I think) since I seen some studies on the self destructive behaviour of rats who were infected by it, who gained an affinity towards cats, who in turn ate them and shit out a whole new batch. I also think it might go a long way to explaining "crazy cat ladies" since it does seem to cause a neurological uproar akin to schizophrenia. (it might also explain lolcats)

Funny to see people like Dawkins talking about it and now this.

I see it as a harbinger of the zombie Catastrophe

[hadespussercats]

I've been harping on about this for quite a few years (about 2005 I think) since I seen some studies on the self destructive behaviour of rats who were infected by it, who gained an affinity towards cats, who in turn ate them and shit out a whole new batch. I also think it might go a long way to explaining "crazy cat ladies" since it does seem to cause a neurological uproar akin to schizophrenia. (it might also explain lolcats)

Funny to see people like Dawkins talking about it and now this.

I see it as a harbinger of the zombie Catastrophe

I've heard about this before.

But I thought it was much harder to get toxoplasmosis than most people think-- that cats only can spread it when they first start hunting, generally (So, if you were surrounded by a colony of cats, you'd be at high risk, but for yer average one to two cat household, especially cats that don't hunt much, the risk is pretty low.)

Of course I don't have the sources handy where I read this. Will look, maybe, later...

[hadespussercats]

Ah-- here's some info:

Because cats only shed the organism for a few days in their entire life, the chance of human exposure is small. Owning a cat does not mean you will be infected with the disease. It is unlikely that you would be exposed to the parasite by touching an infected cat, because cats usually do not carry the parasite on their fur. It is also unlikely that you can become infected through cat bites or scratches. In addition, cats kept indoors that do not hunt prey or are not fed raw meat are not likely to be infected with T. gondii.

In the United States, people are much more likely to become infected through eating raw meat and unwashed fruits and vegetables than from handling cat feces.

http://www.vet.cornell.edu/fhc/brochures/toxo.html

and

Kittens and cats can shed millions of oocysts in their feces for as long as 3 weeks after infection. Mature cats are less likely to shed Toxoplasma if they have been previously infected.

http://www.cdc.gov/parasites/toxoplasmosis/epi.html

[GenesForLife]

I think you heard it from me on the coach, Ronja, while I was also nattering on about nematomorph hairworms.

[Ronja]

Ah, that may very well be! An interesting bus ride it was.

[GenesForLife]

Ah, that may very well be! An interesting bus ride it was.

Aye

[Warren Dew]

Clearly this explains the people who try to break into tiger pens at zoos.

[hadespussercats]

Clearly this explains the people who try to break into tiger pens at zoos.

That... was something else.

He "wanted to be one with the tigers."

I'm glad they didn't destroy the tigers. The zookeepers said, "they didn't do anything wrong."
That's how I see it, too.

Tigers are not our mystical friends. They are tigers. And tigers attack big beasts in their territory.

[hadespussercats]

Oh-- In case you don't know what I'm talking about: http://news.yahoo.com/mauled-man-charge ... 33630.html

[Blind groper]

My concern about cats is more their toll on wild life.
http://www.fieldandstream.com/blogs/fie ... l-wildlife

I live in an area where there are many native birds at risk, and it really pisses me off to see how many of my neighbours insist on keeping cats and dogs. Not nice!

[Ronja]

My concern about cats is more their toll on wild life.
http://www.fieldandstream.com/blogs/fie ... l-wildlife

I live in an area where there are many native birds at risk, and it really pisses me off to see how many of my neighbours insist on not keeping their cats and dogs on leashes or in pens/kennels. Not nice!

.

[hadespussercats]

My concern about cats is more their toll on wild life.
http://www.fieldandstream.com/blogs/fie ... l-wildlife

I live in an area where there are many native birds at risk, and it really pisses me off to see how many of my neighbours insist on not keeping their cats and dogs on leashes or in pens/kennels. Not nice!

.

Thanks, Ronja!

Yeah, my kitty doesn't go outside ever. She may lust at the birdies through the window, but she has to do her hunting indoors.

[DaveD]

My cats go outside, but rarely catch birds. The only ones I've seen them with have been fledglings. I had a chat with someone from the RSPB, to ask if they had any ideas about minimising the damage, and he told me there wasn't any point, that the fledglings were probably abandoned, and that however cruel it seemed to let the cats carry on what they were doing, it was a quicker death for the birds than starvation.
That's in the UK though. Different countries with different wildlife might be.....different.

[Ronja]

My concern about cats is more their toll on wild life.
http://www.fieldandstream.com/blogs/fie ... l-wildlife

I live in an area where there are many native birds at risk, and it really pisses me off to see how many of my neighbours insist on not keeping their cats and dogs on leashes or in pens/kennels. Not nice!

.

Thanks, Ronja!

Yeah, my kitty doesn't go outside ever. She may lust at the birdies through the window, but she has to do her hunting indoors.

My SIL's family lives in a single-family house on a pretty big property and has had quite many cats for several years. About ten years ago they built a chicken-net cage in their back yard for the cats, accessible through a flap in a window. I think the cage was about 2 m x 3 m x 1.5 m and one corner was basically a biggish hut (from a cat's POV), so the cats could be outside but protected from rain and wind, when they wanted to. The net was sunk about half a meter into the ground so they could not dig themselves out. Inside the cage were quite a few pieces of wood and thick rope for climbing and scratching and also some other toys. AFAIK the cage is there still, though they have fewer cats now. Most kittens were sold, and one by one the mother cats have died away - I think there are only three pretty old ones left now.

I understand that not everyone can provide that luxuriously for their pets, but one really should not take an animal if one cannot keep it sufficiently safe, also for its environment. Predators will be predators, and the environments where that is OK are limited.

Hmm... It now occurs to me that a T. gondii infected mouse could probably have wandered into the cage. Probably not a rat, but a small mouse maybe. I'll try to remember to ask SIL or her husband if the cats ever caught anything from inside the cage, when I talk to them next time (that might be around next solstice, though).