The strangest treatment I have ever seen suggested for celiac disease is to purposefully infect people with hookworm parasites. This was actually done in a serious clinical trial in Australia, with results reported in 2011.
The first question that comes immediately to mind is, why would anyone do that? The answer is the so-called “hygiene hypothesis.” This concept is being used to try and explain why allergic diseases and autoimmune diseases are becoming more and more common in many parts of the world, including the United States. The hygiene hypothesis is that children are not exposed to as many germs as they were in the past. Perhaps these infections are necessary to train the immune system to fight the right things. Instead of fighting off infections, the immune system winds up attacking the body (autoimmune disease) or things that are not in and of themselves dangerous, like pollen or pet dander.
It has been observed repeatedly that the lack of infection with common intestinal parasites may be a factor in regards to certain diseases. People with intestinal parasites make more of an immune response to the parasite and less to potential causes of allergy. Worms may confer some kind of protection against autoimmune liver disease. The risk of people with multiple sclerosis getting worse seems to be lower in those with intestinal worms. In laboratory animals, infection with worms reduces a number of autoimmune diseases.
Some researchers have infected people with inflammatory bowel disease with a worm not usually found in people, but in pigs. Because it was not naturally a human parasite, patients had to be reinfected every three weeks which was deemed impractical. There is a related worm called Necator americanus (NA) which lives in the intestinal tract of 500 million people around the world. With large amounts of NA, people become anemic and can have intestinal symptoms. Low numbers of worms do not usually cause symptoms or health problems. These worms do not replicate in humans and can be easily treated and eliminated. They also cannot be transmitted from one person to another unless their stool is in the soil and people are walking on it with bare feet.
This led investigators to try infection with NA in patients with celiac disease. They believed the risk to be minimal and the possibility of improvement worth trying this infection.
The study was undertaken to see if NA infection would be able to lessen the reaction of people with celiac disease to gluten. All of the participants were at least 18 years of age, definitively diagnosed with celiac disease and controlled on a gluten-free diet for at least six months.
The study was a well-designed trial in which participants were assigned randomly to treatment groups. Neither patients nor researchers knew who got which treatment. There were 10 people in the control group, and 10 who received NA (hookworm). The two groups were similar in all important aspects.
Participants got either NA or placebo at week zero or week 12. Blood was checked for high levels of a certain blood cell that increases in parasitic infections, and stool was checked for hookworm eggs to prove that the individuals were infected.
For 20 weeks a gluten-free diet was maintained. Duodenal biopsies were taken during week 20. After that, all participants ate white bread containing 16 grams of gluten a day, for five days. Blood was then drawn and duodenal biopsied obtained a second time. Blood analysis was done to measure the specific T cells that react to gluten in people with celiac disease. This particular test is not usually used at this time except in research.
During this period, participants were followed closely and any symptoms recorded. All ten of the patients were successfully infected. They developed itching at the site where the worms were injected in the skin. This effect was mimicked by injection Tabasco Pepper sauce into the control patients. The patients with hookworm did developed pain which completely resolved by week 16.
Now, to the important results. After gluten ingestion, duodenal biopsies showed abnormalities in both groups. T cells reacting to gluten rose in both groups, with no statistically significant difference. There was no significant difference in symptoms after the participants started eating gluten.
While the infected patients did not suffer any serious adverse consequences, they did not have any benefit from the worm infection.
The researchers concluded that although this did not seem to help people with celiac disease, a similar protocol could be used to test NA infection to see if it helps people with other autoimmune diseases or allergies.
So, for people with celiac disease, nothing can be gained by infection with hookworms.
You can decide for yourself what you think of this study. While I understand the hygiene hypothesis in general, it does not surprise me that people with established celiac disease did not benefit from a parasitic intestinal infection.