However, not everyone believed that Weinstock’s helminths were safe. Some data obtained in animal experiments suggested that helminths that shift the immune response may exacerbate the effects of other infectious agents, such as Campylobacter jejuni. This idea made sense: if helminths shift the immune response towards Th2 where Th1 is required, opportunistic microorganisms are easier to gain a foothold in the human body.
Others have raised concerns about the unpredictability of any helminths, even those that have supposedly adapted to the human body. In some cases, pinworms that live in the human intestine enter the liver and lungs. Parasites that colonize unknown hosts can settle in more unexpected places. Canine helminths are able to enter the lungs and liver of a person. Helminths that live in deer, almost without causing them problems, sometimes kill moose. There have been cases where raccoon helminths have penetrated the human brain, causing neurological complications and death. And even the T. suis helminth, which in most cases does not cause any symptoms in domestic pigs, can migrate to the kidneys of a related species-wild boars.
“It is impossible to predict exactly where T. suis larvae will go in a human, atypical host in this context,” cautioned Herbert van Kruijningen, a researcher at the University of Connecticut. “It may only be a matter of time and number of larvae before a patient who is being ‘treated’ with T. suis develops retinal or [central nervous system] disease. “
Summers and Weinstock disagreed. They objected that there was not a single report in any publication (and presumably in the course of millions of human-pig-headed contacts in Iowa alone) that anything was going wrong. In addition, by that time, about three thousand patients were taking TSO — and none of them reported negative side effects.
However, in 2006, a clinical case report was published of a sixteen-year-old boy who was taking TSO for Crohn’s disease. The teenager swallowed five doses, after which doctors found an adult whipworm in his colon. In their opinion, this should not have happened. Moreover, the symptoms of intestinal inflammation in this patient worsened. His doctors blamed helminth for everything.
Weinstock and Elliott again took a different view. They argued that the inflammation found was most likely due to the disease itself, and not to the treatment method. As for the suspected adult helminth, there were helminths of different sizes in the body of patients who underwent treatment. However, none of the patients had eggs in their feces — the gold standard for determining whether a helminth has reached the stage of puberty.
Essentially, the debate was about acceptable risks. All treatments come with certain risks and, hopefully, benefits. However, given the lack of large clinical trials (they are currently in preparation), no one knows the exact relationship between the risks and benefits associated with treatment through TSO. Weinstock argues that a single larger-than-expected helminth cannot be considered sufficient reason to reject the whole approach, especially given that more common treatments with immunosuppressants such as humira and remicade carry a serious risk of tumour disease, severe infection and death. “There’s nothing wrong with having helminths,” says Weinstock. “Millions of people have them.”
Of course, there is a need for new (some may say “at least some”) methods of treating inflammatory bowel diseases. Even if we leave aside the side effects, existing treatments provide the desired result only in half of cases. And in three out of four cases, people suffering from inflammatory bowel diseases end up having to have surgery.
However, for one person, the potential unpredictability of a helminth adapting to pigs was too much to accept. It would satisfy only the real thing — whipworm, adapted to man.