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Comment by kardos | Hacker News Reader

> It was eating his lunch, so to speak

How does that work. A tapeworm is pretty small relative to your brother (eg by mass), one would think it's caloric needs are similarly small and it would just use a small fraction of his food. Can a tapeworm really consume a significant fraction of an adult's food?

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At the Meguro Parasitological Museum [1], they have an 8 meter long tapeworm [2] extracted from a human. Yes, that is an extreme example and still less mass than a person, but they can get large.

[1] https://www.kiseichu.org/e-top

[2] Visible in the tall blue case here: https://static.wixstatic.com/media/079dcd_843c7597ef244423aa...

Bigger picture of it: https://www.tofugu.com/travel/parasite-museum-tokyo/

The display has a piece of rope, so that you can get a not-too-intimate sense of its length.

there are different types of tapeworms that infect different hosts. cattle tapeworms can grow to 12 feet and much more. It doesn't take much googling to find claims of 100 feet.

google "tapeworm symptom loss of weight" and you will get the recommendation "time to see a doctor"

So the explanation would be that growing is just very metabolically expensive and that is where the deficit goes to?

I'm no expert on invertebrate metabolism, but it does not need to be more expensive than host metabolism, it's simply a redivision of the pizza-pie with more slices going to the growing worm, and fewer slices for the host.

consider the possibility of there being n worms in the host (person), where n is greater than 1, maybe even significantly greater than 1.

so if one worm takes m slices of the pie, and there are n worms in the person, there will be m x n less slices available for the person, which, depending on the values of m and n, could be quite high, and therefore much more detrimental to the person

I thought of a refinement to my previous: tapeworms attach themselves to the host intestinal wall only to secure themselves; however, they feed directly from the food in the digestive tract; they do not "suck nutrients" from the host's bloodstream.

It's not a tapeworm but here's an example of a parasite that does:

https://en.wikipedia.org/wiki/Ancylostoma_duodenale

It's the stuff of nightmares.

That's part of it, but intestinal parasites also interfere with normal digestive processes. Their presence and secretions (waste products and the compounds they use to prevent being digested) can cause a lot of problems. It's common for people with intestinal parasites to have reduced appetite, intestinal inflammation, and digestion issues.

The weight loss isn't just a result of the parasite competing for nutrients, though that doesn't help.

Apart of eating your food directly, anything that can make you bleed internally can cause anemia.

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