how come ‘zombie’ parasites are able to infect species like snails but not humans?
In: Biology
These parasites have evolved very specific genes to be able to carry out their pretty complicated infection. Most zombie parasites tend to stick to one specific organism that they infect (or multiple closely related species), as it keeps their evolution more simple and keeps their genome smaller. The fact that we haven’t observed any ‘zombie’ parasites that infect humans and most higher animals probably means that infecting us isn’t a viable strategy for them to be successful parasites, so they stick to insects and fish. The closest thing to a zombie parasite for humans is rabies, or lyssavirus. It is however not a parasite but a virus.
Because a snail is a much simpler life form than a human. We have so many complex systems that constantly interact to give us life.
Humans DO get parasites, but you’ll see that they usually only affect one part of our life. A stomach bug, for example. It’s really good at attacking that ONE area of our complex biological system, but it can’t fully control us. Our brain is the area that a virus would successfully target for something like “zombification”, and there ARE plenty of Neuroparasites out there (Neuro-parasitology is a fascinating area of study, if you’re interested)
I’d certainly imagine that some virus or bacterium could evolve in a way to harm us further than just one of our systems, but it hasn’t happened yet. Kuru is another great research area for this, but that isn’t a parasite, just folded proteins, which somehow affect us even stronger than a parasite could.
Read up about the British kid who ate a slug for a bet, became paralysed and died because of the parasite living inside the slug.
Very sad.
Mammals tend to have extremely robust immune systems and high intelligence that makes that type of infectious disease unlikely to evolve and successfully spread Last of Us style. However it does exist in the form of Rabies for example.
Meanwhile most invertebrates have more simplistic immune systems and lower intelligence and largely more on quantity over quality. Infectious diseases can more easily take hold and influence them.
There is some evidence that a parasite called Toxoplasma gondii that infects humans from cats also causes changes in behavior in humans infected. In animals, it reduces the fear of the scent of predators and of going out into open spaces, making them subject to higher predation. In humans:
“The authors reported a correlation between *Toxoplasma* and two personalities: lower scores of low superego strength (disregards rules, expedient) and higher scores of Protension (suspecting, jealous, dogmatic). This finding was particularly seen in males [[22](https://www.intechopen.com/chapters/84000#B22)]. The authors further expanded their study by looking at 224 men and 170 women. In men, they noted similar personality shifts as the prior study, though in addition guilt proneness (apprehensive, self-reproaching, insecure) and group dependency (sociably group dependent, “joiner”) were also positively influenced in *Toxoplasma*-infected men. In women, shifts in personality traits include an increase in affectothymia (warm-hearted, outgoing, easygoing), alaxia (trusting, accepting conditions, tolerant), untroubled adequacy (self-assured, placid, secure, complacent), and self-sufficiency (self-sufficient, resourceful, prefers own decisions).
[https://www.intechopen.com/chapters/84000#](https://www.intechopen.com/chapters/84000#)
Do the hosts know they’re infected? I’m sure if the fungus has made it this far it would be able to make the host ignore it while it does what it needs to do to spread its spores.
What I’m trying to say is we are all probably infected but don’t know it.
Have you not seen the Republican party? They can infect humans…
Because fungi cannot survive in our body. Our body temperature is too high and at best fungus can only be on our skin. For those zombie parasite fungi it needs to be on the brain/get to the brain of the organism. However there are bacterium/parasites which CHANGE the human behaviour by affecting our hormones,pituitary or our emotions to some extent. Anger due to steroids for example.
That being said, last of us video game plot basically involves this zombie fungi being adapted to human body temp.
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