Tuesday, August 28, 2012

Autism and the Epidemic of Epidemics: Us, Microbes, and Now Parasites

Humanity has been rather successful at protecting itself from the viral and bacterial invaders who would do us harm. However, somewhere along the way, we have been beset by a suite of other diseases that seem to fall in the noncommunicable category. These diseases are rapidly growing in incidence, seemingly in defiance of our comfortable modern lifestyles. One might include in this category obesity, diabetes, numerous food allergies, asthma, autism, and mental illness. The conditions of obesity and diabetes are interrelated and are generally ascribed to a poor personal lifestyle. It is much harder to associate the other diseases with personal habits.

We recently discussed in Microbes and Us: Health, Disease, Inheritance, and Fecal Transplants a new way of evaluating the human condition. The basis of this approach was to recognize that humans evolved in concert with a suite of bacteria that are an integral part of our human condition. The term coined to describe this human-microbe entity is microbiome.

These microbes perform functions that are critical to our health. Research is beginning to show correlations between the actions these bacteria and a number of noncommunicable diseases. Data is accumulating that indicates imbalances in these bacterial populations, or other malfunctions in their performance, can cause human distress as surely as a malfunction in hormone production, for example. While obesity can be attributed to poor eating habits, that is not always the case. There is evidence of a connection between diseases of nourishment and intestinal bacteria.

Given highly suggestive evidence, but not yet clinical proof, there is great excitement in the medical research community, because there is hope that some of these troubling diseases may ultimately be attributable to a treatable condition.

This research is also of great interest because it suggests a fundamental principle: don’t mess with Mother Nature. We are complex creatures—more complex than we suspected—and minor changes in lifestyle can cause difficulties.

One of the conditions that researchers sought to explain by invoking bacterial action was autism. The hypothesis involved a bacterial imbalance that caused increased consumption of sulphur in the intestines to the point of restricting its availability to the developing brain. That seemed to be pure hypothesis.

Another hypothesis with respect to autism was encountered shortly thereafter which seems to have a host of suggestive data to support it. It is interesting in that it also postulates a cause associated with modern deviation from the traditional human condition.

Moises Velasquez-Manoff provided a fascinating article in the New York Times: An Immune Disorder at the Root of Autism. He presents this thesis:

"So here’s the short of it: At least a subset of autism — perhaps one-third, and very likely more — looks like a type of inflammatory disease. And it begins in the womb."

"It starts with what scientists call immune dysregulation. Ideally, your immune system should operate like an enlightened action hero, meting out inflammation precisely, accurately and with deadly force when necessary, but then quickly returning to a Zen-like calm. Doing so requires an optimal balance of pro- and anti-inflammatory muscle."

"In autistic individuals, the immune system fails at this balancing act. Inflammatory signals dominate. Anti-inflammatory ones are inadequate. A state of chronic activation prevails. And the more skewed toward inflammation, the more acute the autistic symptoms."

The author indicates several studies that indicate that episodes of inflammation experienced by the mother during pregnancy can increase the probability of autism developing in the infant. Given that modern hygiene has been reducing the incidence of infections, while the number of autism diagnoses is growing rapidly, suggests a more subtle connection.

"Better clues to the causes of the autism phenomenon come from parallel "epidemics." The prevalence of inflammatory diseases in general has increased significantly in the past 60 years. As a group, they include asthma, now estimated to affect 1 in 10 children — at least double the prevalence of 1980 — and autoimmune disorders, which afflict 1 in 20."

"Both are linked to autism, especially in the mother. One large Danish study, which included nearly 700,000 births over a decade, found that a mother’s rheumatoid arthritis, a degenerative disease of the joints, elevated a child’s risk of autism by 80 percent. Her celiac disease, an inflammatory disease prompted by proteins in wheat and other grains, increased it 350 percent. Genetic studies tell a similar tale. Gene variants associated with autoimmune disease — genes of the immune system — also increase the risk of autism, especially when they occur in the mother."

The author suggests the principle question to be answered is:

"Why are we so prone to inflammatory disorders? What has happened to the modern immune system?"

The answer seems to be associated with modern humans diverging from the conditions under which they evolved.

"There’s a good evolutionary answer to that query, it turns out. Scientists have repeatedly observed that people living in environments that resemble our evolutionary past, full of microbes and parasites, don’t suffer from inflammatory diseases as frequently as we do."

"Generally speaking, autism also follows this pattern. It seems to be less prevalent in the developing world. Usually, epidemiologists fault lack of diagnosis for the apparent absence. A dearth of expertise in the disorder, the argument goes, gives a false impression of scarcity. Yet at least one Western doctor who specializes in autism has explicitly noted that, in a Cambodian population rife with parasites and acute infections, autism was nearly nonexistent."

"For autoimmune and allergic diseases linked to autism, meanwhile, the evidence is compelling. In environments that resemble the world of yore, the immune system is much less prone to diseases of dysregulation."

The author arrives at this general conclusion:

"Since time immemorial, a very specific community of organisms — microbes, parasites, some viruses — has aggregated to form the human superorganism. Mounds of evidence suggest that our immune system anticipates these inputs and that, when they go missing, the organism comes unhinged."

Given this assumption, a path back to normality would include an attempt to reproduce the conditions experienced when humans were fully loaded with their complement of bacteria, parasites and viruses. The author refers to this as an "ecosystem restoration project."

As it turns out, some are experimenting with the reintroduction of parasites in an attempt to counter this inflammatory response in autistic adults. The work of William Parker of Duke University is referenced.

"Dr. Parker has more radical ideas: pre-emptive restoration of "domesticated" parasites in everybody — worms developed solely for the purpose of correcting the wayward, postmodern immune system."

"Practically speaking, this seems beyond improbable. And yet, a trial is under way at the Montefiore Medical Center and the Albert Einstein College of Medicine testing a medicalized parasite called Trichuris suis in autistic adults."

"First used medically to treat inflammatory bowel disease, the whipworm, which is native to pigs, has anecdotally shown benefit in autistic children."

Medical science is getting stranger and stranger.

It is encouraging to be able to begin to think of autism as a medically treatable condition.

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