By Dr. John Weiner
The hygiene hypothesis has got a lot to answer for. Feeding worms to experimental subjects for one.
How did the hygiene hypothesis start? From one of the most boring specialties in science – statistics (no mail please). It was the epidemiologists who first alerted us that children in developing countries, and even in eastern European countries (pre-Glasnost) had less allergy and asthma.
Subsequently the links appeared between less allergy and large families, later birth order in families, early childcare, less antibiotics, less vaccination, more parasites…whoa….more parasites! This is where we come in.
There is something unpleasantly visceral about parasitic worms living inside you. But the stats showed humans with parasitosis and eosinophilia (the bodies natural protection against parasites) had less allergy. And, yes, less autoimmune disease.
Enter Necator americanus, the hookworm. Responsible for chronic anemia and failure to thrive in millions of people, but, apparently, small numbers are harmless in healthy humans. Just so you know, the eggs hatch in the soil, the small larvae attach to the skin of your foot, these larvae migrate into the skin, then lymphatics and bloodstream, rupture into the lung, are coughed up through the windpipe and swallowed into your stomach and become adults in your bowel where they live for years, the females laying about 10,000 eggs a day, which go, well, you know where…
Hey, (thinks) wouldn’t it be great to infect people with this parasite and see if it helped their autoimmune disease… How do we infect them? Well, Juergen Landmann infected himself both orally and via the skin with Ancylostoma caninum, a closely-related hookworm, and reported his observations in the MJA in 2003. The ‘Acknowledgements’ section of the paper states: “Vicki Whitehall, the first author’s wife (fiancée at the time) is thanked for allowing experimentation and sample collection in the bathroom of her rented townhouse” Ahh, true love.
Two previous trials have looked at worm infection in the treatment of asthma and hay fever, with no benefit. Move on to the latest paper on Plos One. Here a group of Aussie scientists enrolled 20 subjects with celiac disease, and inoculated half of them with 15 hookworms in a randomised double-blind placebo study. They were inoculated by rubbing the larva into their skin. This causes an intense itch at the site. So the placebo was McIlhenny Company Tabasco Pepper Sauce, yep, the same stuff I put on my eggs this morning. Infection was confirmed (see figure).
They challenged all subjects with gluten several weeks later. Results? No difference between the two groups. But there were subtle differences in decreased autoimmunity in favor of the infected group. You may be interested in an interview with one of the authors on The Health Report from 13 June 2011.
This was an elegant experiment, no question. I do note that three ethics Committees allowed the trial [“What’s this you say, lead investigator, the subject is inoculated with worms which enter the lungs and are coughed up then swallowed???“] And half the inoculated subjects had painful bowel pain for a while. And, mysteriously, all infected subjects declined anti-worm treatment at the end of the experiment! Go figure.
Me, I’d like a tablet or a needle please, not live worms. Having said that, I have to admit it was a gutsy experiment…
Dr. John Weiner is an allergist and clinical immunologist in Melbourne, Australia. His website is AllergyNet Australia www.allergynet.com.au and he is active on Twitter @AllergyNet, where this piece was originally published.