In 1989, David Strachan, an epidemiologist at St. George’s University in London, published a landmark study proposing that improved hygiene in the developed world could explain trends in hay fever incidence. Strachan’s idea was that changes to sewage treatment, availability of clean water and food, and a shift away from farming lifestyles decreased our contact with soil, faeces and contaminated food where bacteria and parasites like helminths live.
The so-called "hygiene hypothesis" quickly took off, but in recent years a growing number of scientists have said the picture is more complex. The rise in allergies and inflammatory diseases may not necessarily be caused by a general lack of microbes in hygienic environments, but rather by a lack of certain organisms that have, over the course of evolution, trained our immune system to be more tolerant.
One of those organisms could be the worm-like parasite. Many of our human ancestors would have been infected with helminths, as are large numbers living in developing nations today. When helminths infect individuals and attach themselves in their hosts’ gastrointestinal tracts, the immune system launches an attack, while at the same time issuing a chain of anti-inflammatory orders to ensure the response does not get out of hand. People who survived infection have passed on immune advantages to future generations. In the modern, developed and sterile West, the theory goes, immunoregulatory effects no longer develop normally, leaving some particularly vulnerable to allergies and inflammatory diseases. “It’s not that you’re diseased or abnormal, it’s just that the world has changed,” says David Elliott, hepatologist at the University of Iowa, and Weinstock’s research colleague.
In 1999, when Elliott and Weinstock first found that helminths protected mice against colitis, news spread fast. Six years later, the group published the result of two preliminary trials in humans. In one, involving 54 ulcerative colitis patients, 43% of those given pig whipworm eggs improved, compared with only 17% who received placebos. In a second trial 29 patients with Crohn’s disease took whipworm eggs every three weeks. By the end of 24 weeks, 79% had reduced disease activity and 72% had gone into remission. Researchers and biomedical companies around the world began to investigate the potential of helminthic therapy for treating conditions ranging from asthma to autism to psoriasis.
Helminthic therapy is still at the experimental stage, but some patients are unwilling to wait. In 2007, self-infected entrepreneurs Garin Aglietti and Jasper Lawrence founded a worm therapy start-up called AutoimmuneTherapies in the US by harvesting hookworms plucked and sterilised from their own faeces, and charging between $2,000 to $3,000 per dose. However in 2009, the Food and Drug Administration defined helminths as biological products that could not be sold before having undergone a series of clinical trials, which they had not. Aglietti set up his own WormTherapy operation to Tijuana, Mexico, and Lawrence returned to his native England.
Herbert Smith, a financial analyst in New York bought hookworms, and pig and human whipworms from WormTherapy and AutoimmuneTherapies, either travelling to Mexico or receiving mail-order worms from Lawrence. Smith was diagnosed with Crohn’s disease in 1996, and lost a foot of his intestines to surgeries before he stumbled on one of Weinstock’s papers. Today, he maintains a healthy population of hookworms, which he says have caused a complete remission. “This therapy could help people who don’t have any other treatment options,” Smith says.
Not everyone responds so well, however. Moises Velasquez-Manoff, a journalist, also visited Aglietti’s Tijuana clinic to receive a dose of 30 hookworms for his allergies and asthma, and to chronicle the experience in his book, An Epidemic of Absence. Once infected, he suffered diarrhoea and a dull, constant gut pain, and his allergies failed to improve. After a year and a half he took medication to flush out the invaders. “The idea is very, very powerful,” Velasquez-Manoff says. “They just weren’t doing anything for me.”