What's a good structure for biological parasitic mind control

Question

So I thought up this alien parasite that enters through the mouth (usually of a predator) where it attaches to the throat and simultaneously takes control of the brain and replaces the esophagus of the victim. It basically sends the unfortunate host into a feeding frenzy, eating as much as possible, with the alien worm-like parasite taking in all the food. Obviously the host will eventually die from starvation and the parasite then lays her eggs in the carcass, her many offspring feeding off of both the carcass and the meat stored in the mother from the feeding frenzy.

The two problems I face are obviously the infection of the parasite and the structure used to control the brain. This question focuses on the latter.

The parasite doesn't control everything, it only forces the creature into a frenzy. If the creature was sentient, it would be too overcome by said frenzy to be able to speak, however most other cognitive functions, reflexes and instinct as well as use of tools are active. The host is not a fumbling zombie, if the parasite infected a tiger it would be just as lethal, maybe even more so, than an uninfected tiger. The host is basically still in control, but under an extreme influence, their mind is given a single drive and they do everything it takes to follow it.

The question I'm asking is, what kind of structure or process would facilitate this kind of 'control' over the host?

Please, if you don't understand my question tell me what I'm missing so that I can edit it to suit.

Answer 1

One potential thing to look at is having multiple symbiotic parasites at work.

The first, the larger parasite that eats all the food, is a macroscopic beast that's parasitic by nature and inhabits the oesophagus. It also introduces a series of potential infections to the body, leading to an immune response focused on it.

The second is an unrelated but symbiotic parasite that inhabits the blood and causes symptoms such as aggression, hunger, hypersensitivity to touch and shutting down the portions of the brain responsible for impulse control.

These two parasites work well together: The first gets an increased food supply, the second gets an excellent transmission vector and a weakened immune system to have a go at. Whereas the first parasite might not be able to deliver effective mind control (due to distance from the brain, blood/brain barriers getting in the way, hormonal imbalances etc) the second parasite is in exactly the right place to drive creatures crazy, and while the second parasite might not be able to capitalise on the neurological/behavioural effects it has the first parasite can easily make use of the increase aggression and hunger.

Symbiotes. Better together.

That neatly

Answer 2

The parasite (alien or Earthly) would need to use chemical messages for this purpose. There are already a vast number of parasites which change the behavior of their hosts.

OK wait! You wrote that the parasite replaces the esophagus of the victim. This already means that no artificial chemical messaging would be required. It goes like this:

The victim eats and gulps down food => The parasite takes that food into its own body (since it is the esophagus) => The victim does not get the fulfillment it gets after eating (the stomach does not release the "I am full now" chemicals in the blood) => The victim still feels hungry and eats again => The parasite takes that food too => With time the victim gets more and more hungry as its stomach is not getting any of the food it is eating.

This is a simple chain with no requirements for any extra chemical messaging. Still, for further information on behavior changing parasites, I recommend reading these:

Introduction To Behavior Changing Parasites (Scientific American Article)

A Nat-Geo Article On Behavior Changing Parasites

BBC Earth Article About Behavior Altering Parasites

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Edit To Add

With such complex creature as a mammal, probably the only way you could urge it for something would be hormones. Hormones are released directly in the blood flow, so you don't have to take over the whole nervous system or anything like that. If you keep releasing small amounts of insulin in the creature's bloodstream, it would keep the host's blood sugar level down and make it feel very hungry. Just make sure you do not release excessive amounts which would make it too weak to walk or hunt.

If you want to make your host more vicious and aggressive, you would need to release some amounts of androgen or estrogen (male and female hormones respectively, raising reproductive urges). These hormones, besides putting a creature (specially mammals) highly focussed on procreating, also make it more aggressive (as a side effect).

Answer 3

There are a couple of good models for what you are suggesting:

• Zombie Ants

• Rabies

• Drugs

There are a lot of drugs that cause hallucinations and/or aggression. Those would be good models.

All of these work by hijacking the hosts systems in order to propagate themselves. Imagine the parasite taking over the system and then releasing PCP and adrenaline into your bloodstream while at the same time preventing food reaching your stomach. An animal is going to stand no chance and even a human would struggle to control the results and distinguish hallucination from reality.

Answer 4

Leptin is a hormone that causes one to feel 'full' after eating. Having a leptin blocker for the receptors or a hormone that reduces the ability of the body to produce this hormone can have an interesting affect.

People could eat themselves to death (in theory) trying to banish the feeling of hunger. CSI had an episode where a man with this problem occurring naturally did just that. Not sure how likely that would be in truth. But add in a few other chemicals, and it makes it more possible. Such as adding in psychotropic drugs, or even just reducing the blood sugar to the brain, would severely dampen the control centers and doing stupid things would be much easier, including being aggressive in acquiring food to fill the void.

The one problem with the parasite 'replacing' the throat would be all the food is STILL going inside the host. Filling it up. It also takes a LONG time for a host to die of starvation, a human can go weeks without eating. Dying of starvation also makes the host less nutritious for the parasite once it dies. By messing with the hormones, the parasite doesn't need to stop the food from entering the host digestive system. It just puts them into overdrive until they eat themselves to death. Then they have a 'healthy' host and all the food they acquired to feast on, in a relatively short period of time.