My partner researches one parasite named in this study (a type of whipworm) and they actually get their eggs for in vitro work from another researcher abroad who infected himself with the parasite because he finds it helps with his autoimmune disease. He harvests the eggs and distributes them to other teams.

There is a significantly more mainstream but similar-in-the-broad-strokes theory, the Hygiene Hypothesis, which says that the immune system relies on encountering things like this for calibration, but doesn't require them as a continual presence for optimal functioning.

Intuitively it wouldn’t be surprising that there’s some symbiosis going on somewhere and that there would be beneficial parasites. In reality I have no idea.

Doesn't seem too off from gut micro biome theories.

I would argue that parasites only became ubiquitous when we abandoned our hunter gatherers way of life and settled into agricultural communities of larger scale (something relatively recent when compared to human evolution).

So, I doubt that immune system theory, since for most of mankind’s existence, they were not part of our life.

The average body temperature then was also higher.

> I can create hypothetical cases for either location to be higher or lower than the other.

- Transmission is easier in the city due to closer contact and more shared resources.

- Urban parasites are likely to be more debilitating to the victim because they may come from an unfamiliar environment. (Compare how hookworm in the American south was a nuisance to blacks, but debilitating to whites.)

We know that diseases were a much heavier burden in cities than they were in rural regions. Parasites are mostly just bigger diseases; you'd need to come up with a really interesting idea to explain why they were a smaller issue in cities than outside of them.

Hookworm is an interesting example to consider here; you catch them by stepping on soil with your bare feet. Stereotypically they are a problem of the rural south. But I found this paper on "neglected tropical diseases" in the United States, which had this to say:

> Toxocariasis is a soil-transmitted helminth infection [it isn't hookworm, but hookworm is also a soil-transmitted helminth infection] that can result in visceral larva migrans, visual impairment from ocular larval migrans, or a condition that resembles asthma, known as covert toxocariasis. Urban playgrounds in the US have recently been shown to be a particularly rich source of Toxocara eggs, and inner-city children are at high risk of acquiring the infection.

https://journals.plos.org/plosntds/article?id=10.1371/journa...

Another example to consider might be covid, where my read of the consensus is that (1) initial nature -> human infection is more likely in rural areas (where there's more nature), but (2) once it can live in humans, it's a bigger problem in urban areas (where there are more humans).

Your ancestors probably had plant-based cures like garlic or walnut hulls for the same infections. Modern medicine improved on the spectrum of parasites that can be treated but there's still some caveman-level stuff that works reliably for some species.

Why are you taking anti-parasitics regularly?

Words have become the canvas ads are painted upon.

Prevalence by existence. A coarse but realistic heuristic for very small sample sizes.