Saturday, October 31, 2009

Johne's Disease (and MAP) in as Many as 70% of U.S. Herds

I saw an article today that shared some startling news about the spread of Johne's Disease. In the last 15 years (from 1996 to 2009), the prevalence of Johne's has increased from only 22% to as much as 70% of U.S. dairy herds. Johne's Disease is caused by the MAP bacteria (see previous blog posts), which many people have found links with to Crohn's Disease.

Here's an excerpt:
"Studies showed that in 1996, Johne's disease was in about 22 percent of the U.S. herds, but because of rapid expansion of herds across the country, producers unknowingly purchased young heifers and older cows which were infected with the disease and thus has raised the prevalence of Johne's to be present in nearly 70 percent of the herds," she said.
Could the recent rise in Crohn's Disease be linked to this rise in the spread of MAP?

Thursday, October 29, 2009

Anti-TNF Drugs Don't Seem to Increase Cancer Risk

Good news for those that use TNF-blockers to manage their Crohn's disease. Long-term use of the drugs (at least for 6 years or less) does not appear to increase your risk of cancer. That's certainly a concern as TNF is part of the body's immune response in dealing with "tumor"-like cells. The study looked at both short and medium term use of these drugs for rheumatoid arthritis and didn't find any elevated risk of cancer.

UPDATE: (6/21/2010) - The FDA released a cancer warning for TNF-blockers back in August 2009. See this related post. Thanks to the anonymous person that commented!

Scientists Link Diet and Immune System

Saw this article about Australian scientists that found a "direct link" between diet and how the immune system functions. The scientists found that a specific short-chain fatty acid (created when bacteria breaks down dietary fiber) binds with an immune cell receptor to influence immune response. The article didn't provide many details on the exact findings, but they were hopeful that it could help explain how dietary changes could be a contributing factor in the rise of autoimmune disorders.

Here's an excerpt:

"When (immune cells) go bad they cause inflammatory diseases, so asthma, rheumatoid arthritis, inflammatory bowel disease ..." Prof Mackay said.

"We think one of the mechanisms for their normal control is short chain fatty acids binding to this receptor.

"And if we were to speculate on the real significance of this, we believe firmly that the best explanation for the increase in inflammatory diseases in western countries ... is our changes in diet."

A lack of dietary fibre could also be behind the rise in type 1 diabetes, Prof Mackay said.

The research suggests that having a healthy diet rich in fruits, vegetables, grains, nuts and seeds would reduce a person's risk of autoimmune disease.

Wednesday, October 21, 2009

Gut Bacteria Linked to Immune Response

Just read this article about a new finding of a bacteria linked to a specific immune response in mice. The bacteria induced higher Th17 response. The finding suggests additional bacteria to look at in the formation of autoimmune disease. Here's an excerpt:

If the effect is present in humans, it suggests a clinical use for the findings, Littman said. "So you can immediately see some practical application of this, if one can mimic the presence of these commensal bacteria to strengthen resistance to pathogenic microbes," he said.

On the other hand, the level of the microbes could also play a role in the development of autoimmune disease, he said. "You have to have the right balance," Littman said.

With hundreds of strains of bacteria, the "right balance" seems very difficult to find.

Thursday, October 8, 2009

I'll Take a Parasite Please: Helminthic Therapy and the Hygiene Hypothesis

I've been wanting to post on this topic for a while, but never got around to it. I just saw this article in ABCNews titled "Allergy Desperation: I'll Take a Parasite, Please" (linked to from this blog post). It includes a story of a guy named Jasper Lawrence who in desperation from long-term allergy problems decided to infect himself with hookworms. The result was that his symptoms were dramatically diminished (if not cured). Why?

Here's a good excerpt from the article that sums it up:
The hypothesis goes that until recently, humans were fighting off some sort of parasite or another for millions of years, ever since humans evolved into humans. That co-existence eventually led humans to evolving an immune system that worked with parasites.

"When you're born you have an immune system, but your immune system is a blank slate," said Weinstock.

Weinstock explained that just as humans create a functioning digestive system by populating their digestive system with bacteria, humans historically developed an immune designed to account for parasites in the body.

But in the last 150 years, the industrialized world's clean food supply and plumbing suddenly removed parasites from people's bodies. In response, researchers now widely think that people's immune systems stopped developing properly.

Weinstock said most people still have a powerful "attack" function of their immune system, but that many believe the immune system does not develop to regulate properly in the absence of helminthes (parasitic worms).

"People who are not exposed to helminthes have sloppy regulation," said Weinstock. As a result some people's immune systems go off kilter and misfire against their own bodies creating autoimmune disorders such as allergies, asthma, or inflammatory bowel disease.
There has been a lot of research into this area and the general "hypothesis" mentioned has been around since the 1980's. The theory is called the hygiene hypothesis. Basically, our overly hygienic lifestyles in developed nations (particularly in the northeast) means that our immune systems have not been properly balanced and exposed to regulating agents. The lack of this exposure causes all sorts of downstream effects when your body encounters mostly innocuous allergens -- basically it over-reacts. The type of therapy described in the article, helminthic therapy, is meant to correct this problem (albeit later in life than probably should have been the case).

In helminthic therapy, you purposely expose the body to parasites such as hookworms. This exposure forces the immune system to develop the proper regulation systems and as a result it no longer over-reacts.

Sounds great! Pass the bowl of hookworms over so I can load up. Perhaps not so fast. Immune development is really complex and many of these parasites can have serious side effects (... they are parasites after all ...), so it's likely wise to wait for many of the clinical trials underway to be completed. You never know, within a few years you may find hookworms in the same category as probiotics!

Wildlife May Cause Livestock Infections of MAP

A study by Scottish researchers found a possible source of Mycobacterium avium paratuberculosis (MAP) infections in livestock -- wild animals. The transmission of infection may be from wild animals to livestock to humans.

DNA Test Results May Not Be As Reliable As They Appear

Just saw an article in the LA Times about how much you can trust new consumer DNA tests. The article highlights a recent experiment that compared the results of two of the leading vendors in this space, Navigenics and 23andMe. The experiment found that in some cases the two vendors conclusions about disease susceptibility was in agreement, but in others it was wildly different. The reason: each company uses different research studies to draw their conclusions. So, one might say that you have a 25% chance of developing Crohn's while the other says something higher. So although both companies do a great job of reading your DNA correctly, the determination of disease susceptibility is simply not a perfect science. In many cases, particularly those where definitive cause is unclear (like Crohn's), it's far from perfect and can generate very different results.