Why Some Parasites Are Actually GOOD (And Which Can Kill You)

SciShow2 minutes read

Parasites can be beneficial or harmful, with some living in symbiotic relationships inside our bodies, aiding in bodily functions like digestion and protection. While some parasites can cause severe diseases and manipulate host behavior, research shows that certain infections may have beneficial effects on the immune system, potentially reducing the risk of autoimmune conditions and allergies.

Insights

  • The human microbiome consists of beneficial organisms that aid in various bodily functions, such as killing harmful bacteria, forming protective coatings, aiding in digestion, and facilitating vitamin absorption.
  • Parasitic infections, while often harmful, have been linked to potential benefits like reduced rates of allergies and autoimmune conditions, suggesting a complex relationship between parasites and the human immune system that may have significant implications for medical research and treatment development.

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Recent questions

  • What are parasites?

    Organisms living off other organisms, some beneficial, some harmful.

  • How do parasites affect humans?

    Parasites can have both positive and negative impacts on human health.

  • Can parasites manipulate host behavior?

    Some parasites can manipulate host behavior for their benefit.

  • Are there connections between parasites and mental disorders?

    Research suggests potential links between parasites and mental disorders.

  • Do parasites play a role in immune system function?

    Parasites may influence immune system function and responses.

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Summary

00:00

"Beneficial and harmful parasites in human bodies"

  • Parasites are organisms that live off other organisms, some of which can be beneficial while others harmful.
  • Mutualistic symbiotic relationships involve animals living inside another animal to help them, like the 100 trillion microbes in our bodies.
  • The human microbiome consists of these beneficial animals living inside us, aiding in various bodily functions.
  • Good parasites in our bodies kill harmful bacteria, form protective coatings, and help in digestion and vitamin absorption.
  • Doctors now diagnose bad gut bacteria and conduct fecal transplants to introduce good gut bacteria.
  • Commensal symbiosis involves animals living in us without causing harm, like eyelash mites feeding on oils without affecting us.
  • Parasites that feed on humans can be protozoans, worms, crawly bugs, or other freaky organisms.
  • Protozoans like the brain-eating amoeba can cause severe diseases, while worms can lead to debilitating conditions like elephantiasis.
  • Crawly bugs like bed bugs or body lice feed on us externally, causing discomfort but are less likely to be fatal.
  • Some parasites, like the cuckoo catfish or cuckoo birds, engage in brood parasitism, laying eggs in other animals' nests to raise their young.

12:32

Parasitic Manipulation and Mental Health Risks

  • Green banded broodsack larva infect birds, leading to snails being manipulated into becoming zombie hosts to attract birds for the larva's reproduction cycle.
  • Hair worms infiltrate insects like grasshoppers, manipulating their brains to commit suicide by drowning, allowing the worms to return to water for reproduction.
  • Toxoplasma gondii, found in cat feces, manipulates rats to be attracted to cats, potentially affecting human brain chemistry and possibly linked to increased schizophrenia cases.
  • Toxoplasmosis can infect humans through cat feces, leading to mild flu-like symptoms or severe effects like muscle weakness, seizures, and brain damage.
  • T-gondii infection in pregnant women can pass on to babies, potentially causing psychological conditions like depression, anxiety, and self-harm.
  • T-gondii affects neurotransmitters, potentially leading to imbalances linked to mental illnesses like psychosis, schizophrenia, and bipolar disorder.
  • T-gondii infection can disrupt neurotransmitter functions, leading to excitotoxicity and neurodegenerative diseases like ALS, multiple sclerosis, Parkinson's, and Alzheimer's.
  • Research on the link between toxoplasmosis and mental disorders is inconclusive, with some studies showing no significant association.
  • Heartworm disease in dogs, caused by parasitic nematodes transmitted by mosquitoes, can lead to heart failure and other complications if untreated.
  • Humans can be infected with heartworms, but our immune systems typically recognize and destroy the larvae before they can mature, making human infections rare.

25:41

Parasitic Worms and Immune System Balance

  • Some doctors have found a connection between having parasitic worms and not having immune system problems like allergies or arthritis due to the hygiene hypothesis proposed in the 1980s, suggesting that our immune systems might be out of balance from being too clean.
  • Parasitic worms, collectively known as helminths, can include tapeworms, nematodes, and flukes, which can cause severe symptoms like anemia, liver failure, or bladder cancer, but some species may have more benign effects on the body.
  • Studies have shown that rates of asthma and allergies are higher in places with fewer parasite infections, indicating that our immune systems may have evolved to function with certain parasites to some extent, potentially reducing the risk of autoimmune conditions and allergic responses.
  • Parasitic worms may trigger regulatory mechanisms in the body that reduce inflammation and overreactions to allergens, potentially offering insights for developing treatments for autoimmune diseases without the need for actual worm infections.
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