Hiding Inside - Toxoplasma gondii(トキソプラズマ)(弓形蟲感染症)

Hiding Inside - Toxoplasma gondii(トキソプラズマ)(弓形蟲感染症)

As a kid, instead of being amused by princesses and unicorns, I was a huge fan of any movie or series that featured weird creatures, like V or Aliens, the SciFi horror movie.
Soon enough I realized that unfortunately, aliens do not exist (as far as we know), but I learned that I did not need to go to space to find equally fascinating (and deadly) creatures. These organisms have proven to be selfish, cause no good to whoever gives them shelter, and some of them show a remarkable taste for our nervous system. They are parasites.
There is a long list of parasites that can potentially camp out in our brain and/or spinal cord, causing considerable damage if untreated. Some of those are considered by the CDC (Centers for Disease Control) to be responsible for “Neglected Parasite Infections” in the US, which have known effects on the human nervous system.
Toxoplasma gondii (T. gondii) is one of those parasites. According to the CDC, 60 million people, in the US alone, may be infected with this parasite. A person with a healthy immune system may not even notice the infection, however, pregnant or immunosuppressed patients need to be especially careful as the effects of T. gondii can be very serious.

The manipulator

T. gondii, is an intracellular parasite responsible for toxoplasmosis. This parasite is capable of manipulating the host’s behavior. For instance, rats are normally repelled by cat urine as a biological mechanism of defense; however, rats infected by T. gondii seem to turn suicidal and are actually attracted by the cat urine scent. This makes the infected rats wander into a cat’s territory, putting themselves at risk of being devoured by their predator. This manipulation of the behavior of the rat, an intermediate host, is a strategy by T. gondii in order to get to its definitive host, the cat. It is there, inside the cat, where T. gondii can complete its life cycle.



But how is T. gondii capable of this sort of manipulation? Apparently, this microscopic parasite produces a protein that synthesizes the precursor of dopamine, thereby, increasing the levels of this neurotransmitter in the brain and impairing normal circuits that would keep the rat away from cats.
T. gondii has been related to personality changes in humans, as some studies show that people infected were more outgoing to the point of recklessness; they even seemed to get into more traffic accidents. However, the ways that T. gondii affect their hosts seem to be dependent on the length of the infection (the longer the parasites lives in its human host, the more acute those personality changes are) and the gender of the host (women and men displayed almost opposite personality changes when infected by the parasite).
T. gondii infection has been related to schizophrenia, a neurological disorder with multiple contributing factors: genetic, environmental, and infectious. Although much research has been done, it is still unclear whether T. gondii increases the risk of suffering from schizophrenia, or if schizophrenia patients are more prone to get infected by T. gondii. Either way, it is very likely that T. gondii is not the sole key to solve the mechanisms behind schizophrenia.
However, the theory that T. gondii can manipulate human behavior appears to be under some controversy, as some studies have questioned whether this parasite is capable of influencing human behavior like it does on rodents.
A very recent study has also shown how T. gondii can induce two hallmark signs of Alzheimer's disease in rodents: hyperphosphorylation of the protein Tau, and accumulation of the protein beta-Amyloid. This potentially predisposes the host to suffer from this disease. These findings are also controversial, as several other research groups found no correlation between the infection and a higher incidence of Alzheimer's.

Not all is about behavior

T. gondii will infect humans who eat anything contaminated with the eggs of T. gondii, or simply getting in touch with the feces of rodents or cats that are infected. It does not represent a threat to people with healthy immune systems, besides the above-mentioned possible effects on behavior. However, the consequences of T. gondii infection in immunosuppressed patients (e.g. suffers from AIDS or going under chemotherapy) or pregnant women can be catastrophic.


After entering the host’s body (known as the acute phase of the infection), if your immune system is on point, the parasite is rapidly eradicated. If the parasite reaches the central nervous system before it can be destroyed, it forms cysts in neurons.
If the host is immunosuppressed, their immune system is incapable of destroying the parasite and the rupture of the cyst will cause reactivation of the infection and subsequent tissue damage. It can cause microcephaly, a collapse of the brain due to leakage of cerebrospinal fluid, cortical atrophy (dysfunction of the outer layer of the brain), and amorphous calcification (deposits of calcium in the brain, forming “brain stones”).
Infection in a pregnant woman could end in abortion, stillbirth or prematurity. If the baby makes it, the list of conditions goes from microcephaly to respiratory, renal and hearing defects, plus many others that would affect the heart, the nervous system, the skin, the eyes, and even the blood.
In conclusion, behavioral changes or not, infection by T. gondii can be serious, so be tidy next time you change your cat litter.

References

https://www.psychologytoday.com/us/blog/brain-chemistry/201805/hiding-inside-toxoplasma-gondii

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人と動物の共通感染症に関するガイドライン
https://www.env.go.jp/nature/dobutsu/aigo/2_data/pamph/infection/guideline.pdf

トキソプラズマが人の脳を操る仕組み

http://natgeo.nikkeibp.co.jp/nng/article/news/14/7449/


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起業したい人は猫のウ●コ食べればできるかも！（良い子は真似しないように、危険です）

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[大阪]野良猫への餌やりから口論となり、同じマンションに住む男性をカッターで切りつけ。(2015/06)
[東京]野良猫に餌をあげ、隣人に注意された事に怒り果物ナイフで切りつけ。(2015/05)
[福岡]「野良猫に餌をやるな」と注意されて激怒し、57歳男性の顔面を殴る。(2014/11)
[静岡]よく公園で餌やりしていた犯人が、市主導で野良猫駆除を行っていた男性の胸倉を掴みカッターで脅す。(2011/03)
[船橋]女性から野良猫の餌やりを注意され、その帰宅を待ち伏せして包丁で刺殺。(2009/08)
[川崎]アパートの大家に餌やりを注意され逆上、大家を刺殺し義理の娘にも重症を負わせる。(2008/06)
[大阪]猫被害の苦情を言いに来たアパートの隣人を包丁で刺す。(2007/07)
[尼崎]猫の餌付けに苦情を言った人の部屋へ包丁を持って押し込み乱闘に。(2005/04)


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猫オタのロリコン勝又拓哉が2005年栃木県今市市で下校途中の７歳の女児を車で拉致して 
わいせつ行為をしたあとに胸をメッタ刺しにして殺害して雑木林に遺棄した残虐な事件 
勝又拓哉の飼っていた希少種の猫の毛が女児の遺体の付着していたことが逮捕の決め手 

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猫オタが起こした猟奇殺人事件「神戸小1女児バラバラ殺害事件」 

猫オタのロリコン君野康弘が2014.年に神戸市長田区で6歳の女児を家に連れ込んで 
殺害してわいせつ行為をした後に遺体をバラバラにしてビニール袋に入れて遺棄した残虐な事件 
君野康弘は飼ってる猫を餌に猫好き女児を家に連れ込んでいた 勝又被告、控訴審も有罪　今市事件で東京高裁 
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2005年12月、日光市（旧今市市）大沢小1年だった吉田有希ちゃん=当時（7）=が殺害された 
今市事件で、殺人罪に問われた鹿沼市西沢町、無職勝又拓哉被告（36）の控訴審判決公判が 
3日午前、東京高裁で開かれた。藤井敏明裁判長は、無期懲役を言い渡した一審宇都宮地裁の 
裁判員裁判判決を破棄したが、被告に無期懲役を言い渡した。 

https://headlines.yahoo.co.jp/hl?a=20180803-03057321-soon-l09