This hypothetical organism would:

  • Be able to control a host using neurostimulus
  • Inhabit the space near the host's brain
  • Be rather large, so it would have to disguise its body in an attempt to match a human body part. Maybe it would approximate hair as best it could?

Signs that a host has this parasite could include:

  • Chemical imbalance of the host such as orange pigmentation of the skin
  • Irrationality or lack of temperament
  • Misperception of own body as an error of the neurostimulus, ex. "I have big hands, I have the biggest hands"
  • Disregard of common sense or common morals
  • A sudden or unexpected change in political power as the parasite makes its way to a position of power

Is this plausible? Could an alien parasite really work in these ways, or be present on a human host disguised within the population?

  • 3
    $\begingroup$ If we assume this has already happened, it almost makes me feel better about the US presidential election at the moment... $\endgroup$
    – SRM
    Oct 19, 2016 at 4:44
  • $\begingroup$ How does our white blood cells interact with the foreign(alien) organisms and how is it related to politic? How can the "intelligent alien" pull strings in one of the most complex social activities that doesn't serve any purpose beside innovating taxes? $\endgroup$
    – user6760
    Oct 19, 2016 at 5:35
  • $\begingroup$ Shhh. Careful the alien's host doesn't get wind of this conversation. He may lock you up for exposing him, or worse press gang you into his political campaign! Look out for some black helicopters over the next few days! $\endgroup$ Oct 19, 2016 at 7:57
  • $\begingroup$ @user6760 Great question which I am not completely sure how to answer, maybe chemical interactions with the brain but you could go in depth in an answer $\endgroup$
    – Zxyrra
    Oct 19, 2016 at 11:24
  • 1
    $\begingroup$ Im suddenly looking at the Donalds hair in new light.... $\endgroup$ Oct 20, 2016 at 11:58

5 Answers 5


Toxoplasma Gondii

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The organism toxoplasma gondii is well known to do almost exactly what you are wondering about. This is not fiction—it is actually a scientific fact on Earth now (except the organism is not considered to be of extraterrestrial origin.) Its most notable characteristics are

So far no concrete evidence has been found that t. gondii effects human behavior, even though half of the world's population is thought to be infected, up to 95% in certain populations. However, there is speculation it could effect human behavior, perhaps even causing schizophrenia and other mental illnesses.

I feel this type of organism could very well already be doing what you are asking about: BDSM, extreme sports, suicide bombings, schizophrenia, bipolar, etc., as well as unwillingness to agree to peace in the Middle East.

Zombie organisms

There are a few organisms, some microscopic, some macroscopic, that cause real zombie behavior:

1. Ophiocordyceps unilateralis

enter image description here

When a spore of Ophiocordyceps unilateralis meets an ant, things get very weird and very bad for the ant very quickly. The spore germinates and enters the ant’s body through holes in its exoskeleton. The fungus then starts to grow inside the ant’s body, absorbing soft tissue while leaving vital organs intact, for the ant must remain alive and fully functional for a while longer to be of real use to the fungus.

When O. unilateralis reaches the autumn of its short life and is ready to sporulate and make way for a new generation, its long, branching filaments grow into the ant’s brain. The fungus produces chemicals that poison the ant’s brain and cause it to become transportation to the fungus’ birthing ground—and its own hearse. The ant, no longer in control of its own body, leaves its colony, climbs a plant, and clamps its mandibles around a leaf at the top, fastening it to its grave. There, new life springs into the world, right out of the ant’s head. Now out in the open, the fruiting bodies of the fungus mature and burst, releasing clusters of spore capsules into the air. As they descend, these capsules explode, spreading spores like confetti over the ground. The spores infect other ants, continuing the fungus’ bizarre life cycle. The whole ordeal, from one infection to the next, can take as little as two weeks.

2. Hymenoepimecis argyraphaga

enter image description here

Normally, the web of an orb weaver spider is where bugs meet their untimely death and become spider snacks. Using an arsenal of toxins and mind-altering chemicals, though, the parasitic wasp Hymenoepimecis argyraphaga turns the spider into a slave and a meal, and its web into a safe haven. The female wasp paralyzes the spider with a sting and then lays her egg on its abdomen. When the egg hatches, the larva lives on the spider and sucks hemolymph (kind of the arthropod version of blood) from its body for nourishment.

A few weeks later, the larva is ready to move on to the next stage of its life cycle, and injects the spider with a chemical (as yet unidentified) that alters its behavior. The next time the zombie spider builds a web, it repeats the first few steps over and over again instead of going through all the regular steps, resulting in a web that’s just a few heavily-reinforced anchor threads and a small center section. Then the spider crawls to the center of the web and sits there complacently. The larva molts, kills the only companion it has ever known, sucks any remaining useful bits out from its corpse, and discards it. Then it builds its cocoon on a web custom-built for the job. A few weeks later, the adult wasp emerges and flies away, and the cycle starts over.

3. Jewel Wasp

enter image description here

Like H. Argyaphaga, the Emerald Cockroach (or Jewel) Wasp is free-living as an adult, but starts life inside a host. As their name suggests, these wasps use cockroaches as living nurseries for their little bundles of joy. When a female wasp is ready to lay her eggs, she swoops in, lands on a roach’s back and plunges her stinger into its midsection. The roach’s legs buckle and it tumbles to the ground, unable to flee or fight back for a short while. This buys the wasp time to play brain surgeon. She slides her stinger through the roach’s head and into its brain, slowly probing until she hits just the right spot. The venom she releases this time doesn’t paralyze the roach; it can move its legs again, but not of its own accord. When the momma wasp grasps its antennae and starts moving, it follows her like an obedient puppy. She leads the roach to her burrow, where she lays her egg on its abdomen and then leaves. All the roach can do is sit and wait. Soon the egg hatches and the larva emerges. It chews into the roach’s abdomen and wriggles inside, where it lives for a week, devouring the roach’s organs the whole while. It forms a pupa and emerges as a full-grown adult a few weeks later, bursting forth from the roach and leaving it buried in the burrow.

4. Glyptapanteles Wasps

enter image description here

The females of the genus Glyptapanteles lay scores of eggs inside caterpillars, and the larva squirm out a short time later to spin their cocoons. It seems like the caterpillar gets off a little easier than those poor roaches and spiders, but its work isn’t done yet. A few of the larva actually stay behind inside the caterpillar and give up their chance to pupate and mature, for the good of their siblings. They take control of their host’s body, and force it to stand guard over the cocoons. The caterpillar waits motionless, unless a potential predator comes too close to the pupae, in which case it thrashes violently at the visitor to drive it away. By the time the adult wasps emerge, the caterpillar, which hasn’t eaten during its guard duty, dies from starvation.

5. The parasitic hairworm

enter image description here

The parasitic hairworm grows up on land—specifically, inside a grasshopper or a cricket—but is aquatic as an adult. To make the transition to water, it forces its host to take it for a swim. The worm pumps the insect full of proteins (which may mimic ones that the host produces on its own) that sabotage its central nervous system and compels it to leap into the nearest body of water. The host drowns and the adult worm, three to four times longer than the corpse it once called home, wriggles out and swims away in search of a mate. The babies they make will infest the water until they're guzzled down by a host they can call their own.


Since these real-life parasitic organisms have the ability to control both the host's consciousness and physiology, even in complex ways, I think it is very plausible another organism could do so to the extent you describe.

  • 1
    $\begingroup$ Not necessarily taking over the world, just ejecting groups of host organism from the country due to cultural beliefs or building a wall, for example $\endgroup$
    – Zxyrra
    Oct 19, 2016 at 4:31
  • $\begingroup$ See Greg Egan’s The Moral Virologist. $\endgroup$
    – JDługosz
    Oct 19, 2016 at 7:58
  • 1
    $\begingroup$ As this answers covers everything i have to say, i'll just leave a quick suggestion: add rabies to the list, it's a viral infection that alters behaviour as well. If a virus can make you more aggressive, and give you cramps and seizures when seeing water (which is super impressive), i am quite sure it could make you strive for power... should be even more possible for a parasite. $\endgroup$ Oct 19, 2016 at 9:10
  • $\begingroup$ Friends don't link friends to mobile wikipedia sites. Just edit the 'm.' out of the URL! $\endgroup$
    – kingledion
    Oct 19, 2016 at 12:07
  • $\begingroup$ Oops sorry, my bad, There, think I fixed em. $\endgroup$ Oct 19, 2016 at 17:31

Well, this is so hypothetical, you can't really say no. There are tons and tons of difficulties with achieving this, and some of them are very technical to an extent unnecessary for the general question.

So many Ways

All the details you suggest could well be one of the ways such an alien could work. It would need to get around the issue of its DNA (if it even uses DNA and not PNA or such) allowing it to work with earth creatures, and humans specifically, to an extent so natural that they are not immediately noticed as behaving uncannily and weird. It has to override parts of the brain's function without ruining the brain's function and control in various areas, you can't suppress the subject's ability to control their blood flow and organs.

Conscious Host?

Some of the things you suggest make it sound like the host is conscious and in control to an extent (or allowed to be) and isn't aware of the parasite. That perhaps your creature cannot control the human brain fully and cannot pose as a human on its own, so it has to manipulate and trick the host. This sounds very interesting, and I think it adds plausibility to the idea. This implies the alien is able to do some pretty good brainwashing/hypnosis via its parasitic connection, and that does raise questions as to how it works so well with the host's brain without them freaking out so much something goes wrong (like they get a heart attack). You can get around that by such means as sneaking up to and paralyzing a host into a coma before attachment, or a tiny parasitic egg learning how to control the host for a long time before asserting proper control.


Again, there is little way to say if it is possible, you can only make it plausible and consider what is technically possible, the more technical you get the more technical the information you need. At maximum technicality, you would literally design an alien creature capable of this, and so there is never need to get close to that far.

I think this is a good concept. I hope this was helpful.


Is this from https://www.rottentomatoes.com/tv/braindead/s01/ ? :)

Or from that bad bad book : https://www.goodreads.com/book/show/13641105-parasite?ac=1&from_search=true ?

The series is fun, in reality to control a person's mind it means to know how it functions and basically we even don't know to much on the brain to use it, so the alien organism must be very knowledgeable, more than human race, to be able to control our brain and through it the body.

Next, to control the culture/politics ... it means the organism is not only some parasite that somehow, let say it grew with our race as a symbiont and adapted to our .. brain?!, but has a large conscious brain that can understand our language and all...

  • $\begingroup$ It not from those sources, no, but thank you for the feedback $\endgroup$
    – Zxyrra
    Oct 20, 2016 at 19:37

If youre interested in more ideas of how to create your story/world with a parasite, look at the anime 'parasyte'


Its about a boy who got infected by a parasite, but that parasite couldnt infect his whole body, unlike other parasites. I think it handles the scenario moderately well.


It isn't easy to design a parasite that could directly mind control a host organism to compel it toward specific actions - brains are extremely complicated and differ from one individual to the next, and parasites are typically not the most intelligent of organisms. There are a lot of parasites that manipulate the behavior of simpler animals, but they usually do this by hijacking a natural instinct that the host has already. This is harder to do with organisms that learn most of their behavior through experience (such as humans).

However, a lot of human emotional responses are controlled by simple chemical triggers, and any parasite that could produce said chemicals could easily modify the mood and behavior of its host. A parasite could make its host more or less prone to anger, compassion, self-restraint, fear, and risk-taking. Pick any drug and a parasite can replicate its effects.

The problem is that humans are very good at detecting abnormal behaviors and socially rejecting people who display abnormal behaviors, perhaps because it is a likely indicator of parasites. So developing a parasite that can make its host better at attaining social dominance could be very tricky. It would have to be subtle enough to fall beneath the radar of most people, while at the same time have enough of an impact to actually make a difference.

One possibility is that the parasite could inhibit serotonin, the chemical that is responsible for feelings of contentment. People who have a serotonin deficiency can be prone to risk-taking, aggression, and sociopathy. They are never satisfied.

Oxytocin is another chemical that could be affected by a parasite. This chemical is associated with trust, compassion, love, generosity, morality, and a great number of behaviors human society calls "good". By inhibiting it, a parasite could basically turn a person into their "evil" counterpart.

So basically, a parasite that inhibits serotonin and oxytocin could turn a person into an uncaring, unsatisfiable, amoral, risk-loving sociopath. If it infected someone who was already smart enough to manipulate people - or someone who had already attained social acceptance and fame before they were infected - it could very turn them into a very dangerous individual indeed.


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