Saturday science subject: Our friends the parasites

Human beings in the civilized world have spent incalculable resources improving sanitation, getting rid of disease, and curbing infant mortality, especially in the past century or so. Those are all undeniably good things, at least from a human point of view. As PhysOrg reports, however, we might have overdone it just a tad in some areas.

The report cites findings by Professors Richard Grencis and Ian Roberts of the University of Manchester. These two researchers say our immune systems start to spaz out without the bacteria and parasites our ancestors had to contend with for millions of years—you know, before hot showers and flush toilets came along. PhysOrg explains:

Intestinal roundworm parasites are one of the most common types of infection worldwide, although in humans increased hygiene has reduced infection in many countries. High level infections by these parasites can cause disease, but the natural situation is the presence of relatively low levels of infection. The team's work suggests that in addition to bacterial microflora, the natural state of affairs of our intestines may well be the presence of larger organisms, the parasitic roundworms, and that complex and subtle interactions between these different types of organism have evolved to provide an efficient and beneficial ecosystem for all concerned.

What happens when something upsets this delicate balance of bacteria, parasites, and immune system reaction? The researchers say we start developing auto-immune diseases and allergies—conditions more seldom experienced in the developing world, where people tend to live in less sanitary conditions.

Reassuringly, the two Professors are sticking on the right side of Hume's Law. Grencis notes, "We are not suggesting that people deliberately infect themselves with parasitic worms but we are saying that these larger pathogens make things that help our immune system."

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