Mind and Body-Altering Parasites

I recently gave a short Ignite-style talk at Synapse Synopsis, focusing on a favorite subject of mine: Mind and Body-Altering Parasites.

I’m not entirely sure why these creatures and behaviors fascinate me so much. I do love being surprised by nature, and seeing adaptations that seem almost improbable (like leaf-mimic insects, for example), so that’s probably one aspect. I also think we can learn a lot about how our own  bodies and minds work through seeing how these creatures are able to manipulate their host organisms. Last but probably not least, there is a morbid fascination here, perhaps my version of what horror-movie-lovers feel when they get a good jump scare. I get the willies reading about these things, but I still love it! I’m not a horror movie fan though. ????

Here’s the presentation itself:

In the process of preparing for this talk I went through quite a lot of research, and since I only had 5 minutes to present, there was a lot I had to leave out. So here I’ll include more info and a bunch of fascinating examples I couldn’t fit into the talk. Enjoy!

Some Great Videos

Naturally many people have covered this subject before me. I tried to focus on organisms not featured in many other videos, but I was definitely in-part inspired by a couple of great videos, including a TED talk and a National Geographic presentation given by one of their photographers.

Human Brain and Body Altering Parasites

Toxoplasma Gondii

There is early evidence suggesting the common flu virus might actually make people more sociable!





Crypt Gall Wasps (e.g. Bassettia pallida)

These are one of my favorite examples, for a couple of reasons. They are local to me (over 800 species in the Americas alone), and they display incredible variety. And I’m just fascinated by how beautiful and unique the growths can be, even on the same plant, just by being influenced by another creature. They’re also one of the places that Hyperparisites show up!

Ladybird parasite (Dinocampus coccinellae)

  • Host: ladybird beetle
  • Modification: brain+body
  • After the wasp egg hatches, the larva chews through the ladybird’s internal tissues before bursting through the abdomen to spin a cocoon between its legs. The ladybird is now a “bodyguard”, standing guard over the cocoon. Still alive despite everything, it will thrash and twitch its limbs if a predator approaches. It’s not clear why it behaves like this, but it may be triggered by venom left by the larva.
  • Rather unexpectedly, a 2011 study found that a quarter of the zombie ladybirds survive the assault.
  • https://www.nationalgeographic.com/science/phenomena/2015/02/10/parasites-within-parasites/ (secondary parasite, virus!)

Castrator Barnacles (Sacculina Sp.)

  • Host: crab
  • Modification: body
  • If the crab is female, Sacculina forces it to care for the millions of barnacle larvae as if they were her own. But if the crab is male, it will be feminised in order to do the same thing. Not only is it rendered infertile, it grows a larger abdomen to carry the barnacle’s young, its gonads shrink, and it stops developing its fighting claws.
  • https://en.wikipedia.org/wiki/Sacculina

Kamikaze horsehair worm (Paragordius tricuspidatus)

  • Host: cricket
  • Modification: brain
  • By altering the functions of the cricket’s central nervous system, the worm coerces it into jumping into the nearest body of water. The hapless cricket then drowns itself, allowing the horsehair worm to emerge and reproduce. Studies suggest that phototaxis alterations (i.e., changes in the responses to light stimuli) could be a part of a wider strategy of hairworms for completion of their life cycles

Green-banded broodsac (Leucochloridium paradoxum)

  • Host: snail
  • Modification: brain+body
  • The green-banded broodsac first squirms its way into the stalks of the snail, so that they look like juicy, pulsing, brightly-coloured caterpillars. This is just the kind of snack nearby birds are in the mood for. Then the worm manipulates the snail’s behaviour. In 2013, Wanda Wesolowska and Tomasz Weslowski of Wroclaw University in Poland found that the infected snails behaved differently from their apparently non-infected counterparts. They positioned themselves in more exposed and better-lit places, situated higher in the vegetation. This probably makes the snails more conspicuous for foraging birds.
  • https://www.youtube.com/watch?v=LGyvlt_b3is Snail eye stalks
  • https://www.youtube.com/watch?v=Hq9PQ0Np6-4
  • https://www.wired.com/2014/09/absurd-creature-of-the-week-disco-worm/

Massospora (fungus)

  • Host: cicadas
  • Modification: brain+body
  • A week after these encounters, the hard panels of the cicadas’ abdomens slough off, revealing a strange white “plug.” That’s the fungus, which has grown throughout the insect, consumed its organs, and converted the rear third of its body into a mass of spores. The de-derriered insects go about their business as if nothing unusual has happened. And as they fly around, the spores rain down from their exposed backsides, landing on other cicadas and saturating the soil. “We call them flying saltshakers of death,” says Matt Kasson, who studies fungi at West Virginia University.
  • He found that the banger-wings were loaded with psilocybin—the potent hallucinogen found in magic mushrooms. Apparently, cathinone (amphetamine) is also produced by Massaspora as it infects periodical cicadas.
  • Infected cicadas behave strangely. Despite their horrific injuries, males become hyperactive and hypersexual. They frenetically try to mate with anything they can find, including with other males. They’ll even mimic the wing-flicking signals of females to lure males toward them. None of this does them any good—their genitals have either been devoured by the fungus or have fallen off with the rest of their butts. Instead, this behavior only benefits the fungus, allowing its spores to find new hosts.
  • https://www.theatlantic.com/science/archive/2018/07/massospora-parasite-drugs-its-hosts/566324/


  • Host: various (incl. humans)
  • Modification: brain
  • Rabies is one of the most frightening parasites, because it seems to blur the line between humans and (other) animals. The virus is spread through saliva, usually from a scratch or bite. It makes animals – usually dogs and bats, and occasionally humans – more aggressive, compelling them to spread the virus through biting and scratching.

Cockroach wasps

Brine shrimp tapeworms

Euhaplorchis californiensis Killifish parasite

Ant Tapeworms

Trypanosoma (sleeping sickness)

  • Host: humans
  • Modification: brain
  • The Trypanosoma alter the structure and function of their hosts’ brain cells (the parasites seem have a particular penchant for the hypothalamus, which helps regulate our mood and sleep/wake cycles) and the hosts start to feel and behave strangely. First they suffer headaches and have trouble sleeping, or sleep and wake at odd hours, due to the parasite’s alteration of the rhythm in which the sleep hormone melatonin gets released. Before long, though, human hosts start to exhibit a dizzying variety of other psychological symptoms, from changing appetites to depression to odd speech patterns to uncontrollable itching and tremors. Over the next few years, the host’s odd behavior gradually starts to lapse into laziness, unresponsiveness, and finally a prolonged sleep that leads to coma and death, hence the name “sleeping sickness.”
  • http://blogs.discovermagazine.com/crux/2015/10/29/parasite-human-brain-control/

Hymenoepimecis argyraphaga (web wasp)

Myrmeconema neotropicum (nematode causing red abdomen on ants)

Phronima Amphipod

Ribeiroian Trematode Flatworm


  • Host: caterpillar
  • Modification: brain+body
  • Virus infects caterpillar, makes it seek high/well-lit area, then liquefies it so it drops down and infects others. Eww. The extensive lysis of cells frequently causes the host insect to literally disintegrate, thus the reason for the historic name “wilting disease.”
  • https://en.wikipedia.org/wiki/Baculoviridae#Baculovirus_life_cycle


  • Host: ants
  • Modification: body+behavior
  • The first instar larvae migrate to the head, where they feed on the ant’s hemolymph, muscle and nerve tissue. Eventually, the larvae completely devour the ant’s brain, causing it to wander aimlessly for about two weeks.[10] After about two[11] to four[10] weeks, they cause the ant’s head to fall off by releasing an enzyme that dissolves the membrane attaching the ant’s head to its body. The fly pupates in the detached head capsule, requiring a further two weeks before emerging.
  • https://en.wikipedia.org/wiki/Phoridae#Lifecycle


Cymothoa exigua (tongue-eating louse)

  • Host: fish
  • Modification: body
  • The parasite severs the blood vessels in the fish’s tongue, causing the tongue to fall off. It then attaches itself to the stub of what was once its tongue and becomes the fish’s new tongue.
  • https://en.wikipedia.org/wiki/Cymothoa_exigua

Lists and Things



Other Interesting Info

Parasite modification of host behavior can also end up modifying behavior of other animals in social groups by proxy.


A more in-depth scientific look at parasitism as an evolutionary strategy in the animal kingdom, with lots of examples, etc.


Last but not least, the most horrifying parasite video I came across in my research.

Author: Oshyan

Food lover and cocktail maker, technology enthusiast, problem solver, entrepreneur, optimizer, photographer and wilderness wanderer.

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