Rat Study Focuses On Hygiene's Role In Disease

[Aaron]

CBC.CA

A comparison of rats living in the wild and the lab lends support to the idea that an overly hygienic environment can lead to allergies and autoimmune diseases.

According to the "hygiene hypothesis," exposure early in life to infections from household dust, germy siblings or surfaces may reduce the risk of developing disease in adulthood.

William Parker, a professor of experimental surgery at Duke University in Durham, N.C., and his team compared lab rodents to more than 50 rats and mice captured and killed in cities and farms.

"Laboratory rodents live in a virtually germ- and parasite-free environment, and they receive extensive medical care — conditions that are comparable to what humans living in Westernized, hygienic societies experience," Parker said in a release.

"On the other hand, rodents living in the wild are exposed to a wide variety of microbes and parasites, much like humans living in societies without modern health care and where hygiene is harder to maintain."

Industrialized societies that emphasize hygiene have higher rates of allergy, asthma and autoimmune diseases such as rheumatoid arthritis compared to the developing world.

Stimulating the immune cells of wild rodents made no difference, but lab rats overreacted, the team reports in the Scandinavian Journal of Immunology.

The wild rodents also showed as much as four times higher levels of immunoglobulins related to allergy and autoimmune disease, but didn't get sick.

Since wild animals are likely exposed to more parasites, the antibodies would likely bind to parasite threats.

But in lab animals, the same antibodies would bind to harmless environmental allergens instead of parasites, leading to allergies, he said.

Looking at differences between animals in the wild and the lab may help scientists figure out what environmental exposures may be protective.

One flaw of the research is the team didn't know if the wild animals were exposed to any unusual diseases that could influence the results.

Pretty much confirms what we already knew, if your too clean it diminishes your immune system.

[Admiral Valdemar]

And leads to an explosion in allergies and auto-immune disorders, like what we have in the first world now. A little dirt now and then did no one any harm.

[Broomstick]

Hee-hee - recently told my mom she shouldn't have been so on-the-spot with the deworming medicine when I was younger.

I actually spent a lot of my childhood filthy, we had dogs, etc.... hmm... maybe I needed more than the typical number of parasites or something.

Is that my problem? I have a parasite deficiency? Will that be the next new addition to children's multivitamins?

[Admiral Valdemar]

I'm reminded now of a picture slide from one lecture involving a toddler and a literal wheelbarrow full of tapeworm being rectally removed. Fire is the only way to deal with that. Lots of it.

[Junghalli]

Heh, I guess the immune system needs exercise, just like everything else.

[Darth Raptor]

When I was in grade school, it did seem like the rich kids got head lice more often than the trailer trash. I always wondered about that.

[Broomstick]

Head lice are unaffected by the immune system.

What's happening there is called "denial". The trailer trash, not being too full of themselves, understand that kids can pick up lice and inspected their brats regularly. When found, they do something about it.

The rich, however, like to think they're superior human beings and that their kids are going to a school "too nice" for such things, or that their little snot-nosed rug-rats aren't associating with those people and so forth. So they don't check the kids, who pick 'em up unnoticed and spread 'em around for weeks before anyone clues in. At which point it's an epidemic.

[Admiral Valdemar]

Actually, head lice typically prefer clean scalps and hair, hence, the kids that wash frequently will be more susceptible to lice than those that wash intermittently and not too well. Dirty hair is something of a turn off for some bugs, but you'll likely get more serious things to worry about if you don't wash too often anyway. Wearing the same clothes for weeks can lead to severe bacterial infections of the dermis.