Parasiidist, mis suudab mõjutada roti käitumist!

Toxoplasma gondii nimeline parasiit elab peamiselt kasside kõhus, kus ta muneb munad, mis väljuvad kassist koos väljaheitega. Munad satuvad sealt edasi rottidesse, kes mullas tuhnivad või lihtsalt midagi söövad, mis on kokkupuutunud Toxoplasma gondii munadega. Aga kuidas saab parasiit tagasi kassi kõhtu, et enda paljunemistsükkel lõpuni viia?

Uurimuste käigus on selgunud, et parasiit jõuab roti organismis ka roti ajju, kus suudab mõjutada rottide käitumist muutes nad vähem kassikartlikuks, seeläbi suurendades tõenäosust, et mõni kass parasiidi poolt nakatunud roti ära sööb. Voíla, täis ring - ainult, et osa parasiite satuvad ka inimestesse ja õhku on jäänud rippuma küsimus: kas Toxoplasma gondii suudab mõjutada ka inimeste käitumist:

Given that human and rat brains have a lot of similarities (they share the same basic anatomy and use the same neurotransmitters), a question naturally arose: if Toxoplasma can alter the behavior of a rat, could it alter a human? Obviously, this manipulation would not do the parasite any good as an adaptation, since it's pretty rare for a human to be devoured by a cat. But it could still have an effect.

Some scientists believe that Toxoplasma changes the personality of its human hosts, bringing different shifts to men and women. Parasitologist Jaroslav Flegr of Charles University in Prague administered psychological questionnaires to people infected with Toxoplasma and controls. Those infected, he found, show a small, but statistically significant, tendency to be more self-reproaching and insecure. Paradoxically, infected women, on average, tend to be more outgoing and warmhearted than controls, while infected men tend to be more jealous and suspicious.

Ühe uurimuse kohaselt võib nakatunud inimeste arv ulatuda kuni 3 miljardini ja esile on kerkinud ka küsimus sellest, millist mõju võib Toxoplasma gondii avaldada inimkultuuri arengule ja mitmekesisusele (PDF):

Differences in risk cause prevalences of toxoplasmosis to vary widely among populations. For example, in the United States, the prevalence of Toxoplasma is higher in the Northeast (29%) than in the south (23%) and Midwest (21%) and lowest in the arid West (18%). Not surprisingly, there is even more variation among nations. This ranges from 81% in France (where raw beef – steak tartare – is a traditional dish) and 79% in Brazil (where climatic conditions are favorable for oocyst survival), to 7% in Japan. It seems possible that differences in personality between my wife and I could partly result from her having grown up in humid, toxoplasmosis rich Brazil and me being raised in arid, toxoplasmosis poor California.

Heh, äkki on prantslased nii kummalised sellepärast, et neid kontrollivad parasiidid?

Üldiselt, järgmine kord kui kassi paitate või aeda mullatöid lähete tegema mõelge sellele - äkki on kassisümpaatsuse põhjuseks hoopis parasiit teie ajus!

(via Marginal Revolution, teadusartikkel via Lund University Library)