In the first experiment of its kind to test the suggestion that hookworm infection can reduce some allergic responses, a UK doctor who specializes in medical entomology, infected himself with the parasite and then swallowed a pill camera to film the effect on his intestines.
Dr James Logan, whose research group at the London School of Hygiene and Tropical Medicine (LSHTM) looks for new ways to control the insects that spread deadly diseases like malaria and dengue fever, agreed to infect himself with hookworm in his debut as a tropical disease expert for the TV show Embarrassing Bodies, a new series of which went out on Channel 4 in March.
In using his own body in the service of science, Logan joins self-experimenters like Sir Isaac Newton, who in the 17th century nearly went blind after staring too long at the sun in a mirror in order to study the after-images on his retinas.
Quite apart from the ethical implications of putting a person’s health at risk, such self-experimentation is much less common nowadays, with trials tending to be on a much larger scale in order to get enough statistical power for reliable results, but, as in Logan’s case, it occasionally happens, under carefully controlled conditions.
Logan was interested in the experiment because research suggests, a hookworm infection can cure or alleviate symptoms of allergies like bowel disease and food allergies. It is thought the worms release compounds that reduce the over-reactions in the immune system that cause the allergies.
He allowed himself to be infected because he himself suffers from a long-standing food allergy that means he cannot eat bread without feeling very ill.
He also wanted to demonstrate, using new state of the art imaging for the first time ever, how the worms get into the body.
The experiment was designed with the help of Dr Quentin Bickle, Reader in Parasite Immunology at LSHTM.
Using state of the art imaging cameras, the team watched the exact moment when the hookworm entered Logan’s skin and made their way into his arm.
It took about two months for the parasites, travelling through his bloodstream, to reach his heart and lungs.
From the lungs, through being coughed up into the throat and then swallowed, the hookworms entered Logan’s intestines where they matured into the adult stage and caused visible damage and inflammation that was recorded by the pill camera that he swallowed.
Tests showed Logan also had higher levels of eosinophils, a type of white blood cell the immune system produces in response to worm infection.
Although the infection gave him some pain, Logan said for the first time in years, he was able to eat bread without feeling ill.
At the end of the 60-day experiment, Logan removed his “guests” with the help of the anti-worming drug albendazole.
He told the press in the run-up to the TV broadcast:
“This is a fascinating area of research for scientists who are studying this phenomenon to try and understand how the worms are able to regulate our immune system and to discover new ways to treat autoimmune diseases.”
Bickle said using the new imaging techniques for the TV experiment gave an interesting opportunity to see how the hookworms entered the skin. It also helped to find out more about “the link between the pathological effects of hookworm infections on the gut mucosa and the potentially beneficial effects of the modulated immune response induced.”
He said more research should help us understand how these mechanisms regulate the immune response, and hopefully lead to new therapies.
According to the US Centers for Disease Control and Prevention (CDC), an estimated 576-740 million people in the world are infected with hookworm. The infection usually has no symptoms, although some people, especially those infected for the first time, have gastrointestinal symptoms.
The most serious effect of hookworm infection is blood loss leading to anemia, and protein loss. The infection is easily treated with prescribed medication.
Click here for a video and further information about Logan’s hookworm experiment as part of the Channel 4 series Embarrassing Bodies.
Written by Catharine Paddock PhD