Hookworms are parasites. But could they also be a revolutionary medical treatment?
In a bright modern office in the University of Nottingham’s complex of bright and modern buildings, Dr David Pritchard has fallen silent and is sitting staring at his hands. It’s been a few minutes
since he stopped talking. In the first 30 seconds I sent off a string of little vacuous questions that hung in the air like soap bubbles, then popped for want of response. Now I’m sitting silent
too, also looking at his hands, considering – as perhaps is he – how much may be within their reach. Dr Pritchard might have at his fingertips a miracle cure for some of the West’s most distressing
and debilitating diseases: Crohn’s disease, multiple sclerosis, lupus and rheumatoid arthritis, as well as severe allergies like asthma, hay fever and the peanut/cat/dust mite allergies that can
make a life miserable. But the curious thing about Pritchard’s cure is that it might equally come to nothing.
Looking at his troubled face, I suspect what’s weighing him down is this chimerical quality: his work could be a godsend, or it could be a dead end; the evidence so far points in both directions.
And it’s not just his own disappointment he has to bear if he’s wrong – there are millions of sufferers out there, waiting for the miracle. Time is not on their side, their medication is often
ineffective and unpleasant. As Dr Pritchard and his team set out on the series of tests which will decide the matter one way or another, I think it’s the weight of their hopes he finds hardest.
While Dr Pritchard trances out, I study a photograph of his cure. It’s not a looker. It’s like a monster from a B movie: slimy, ridged head, lumps where eyes should be, a gaping mouth ringed with
wedge-shaped teeth. But to the naked eye its horrible face is too titchy to be seen because the creature is only a centimetre long. Dr Pritchard’s cure is a worm: Necator americanus or hookworm to
its friends – one of the most common parasites in the developing world.
How could a hookworm possibly be a miracle cure? Most normal people consider Necator americanus to be a problem, a pest which can cause anaemia or stunt a child’s growth. Charities have raised
millions to dose infected kids in Africa and expel the nasty wrigglers.
To see a hookworm, or helminth, as hero, you must first understand something called the hygiene hypothesis – an odd theory that is part scientific, part ideological.
The hygiene hypothesis hangs on a curious fact: autoimmune-related illnesses are far more common in the industrialised West than they are in the developing world. About 50 million Americans have
some type of auto-immune disorder, and that number grows year on year. Very few people in Africa, South America and parts of Asia suffer from such disorders at all. Why might this be? There are two
rough areas in which to look for answers. It could be the things we’ve added in the West: cleaning agents, vaccines, antibiotics. Or it could be the things we’ve swept away in our obsession with
cleanliness: bacteria, disease, parasites.
The two ideas are closely intertwined, but if you’re a hygiene hypothesist you’ll focus on the latter. At the heart of the hypothesis is the idea that we’re not meant to be free from bacteria or
parasites – in this case, most specifically hookworms. We evolved (says the hygiene hypothesist) in tandem with a whole host of wriggling, munching, breeding little critters, who made their home in
our bellies, lungs and guts. In large numbers, an infestation can be life-threatening. But that doesn’t mean we can purge ourselves without creating problems. We and our parasites all evolved to be
part of the same walking, talking, biodiverse little world, they say. We need our creepy crawlies like sharks need the tiny fish that busy about cleaning their gills. Without parasites – or ‘old
friends’, as hygiene hypothesists prefer to call them – our immune system is at a loss, out of whack. Without worms, it begins to overreact and attack friendly cells.
This, then, may well be the origin of our allergies and autoimmune disorders: we are too clean, we’re pining for our ‘old friends’. Dr David P. Strachan developed the theory in an essay in the
British Medical Journal in 1989, and suggested that it might account for not just Crohn’s and MS and rheumatoid arthritis, but also diabetes, psoriasis, ulcerative colitis – even, oddly, autism.
It’s a bold and expansive theory. But is it true? More to the point (especially for sufferers and their families) is it just an explanation, or is it a prescription too? Can a Crohn’s patient or an
asthma sufferer be helped by a dose of hookworm?
Dr Pritchard began by establishing that the worms were safe, which he did by experimenting on himself. A hookworm infects a person by wriggling in through the skin – usually the soles of the feet –
so Pritchard covered a plaster with hookworm larvae, attached it to his skin and let the babies crawl into his bloodstream – where they swam up through his heart and into his lungs, before being
coughed up and swallowed down into his stomach. Once there, they sank their pointy teeth into his stomach wall and began to suck blood. Over a series of tests, Dr Pritchard established how many
worms it’s safe to keep as stomach pets. A hundred was too many (he had awful cramps and nausea), but 25 seemed all right. And because the worms don’t hatch in the gut – eggs must be passed out of
the bowel to complete their life cycle – those ten didn’t multiply.
So it’s safe; but does it work? We don’t yet know for sure. What we do know is that there is a terrific amount of anecdotal evidence – and experiments with mice bode well. Mice with worms produce
regulatory T-cells (T-reg cells) that tell the other, attacking T-cells to calm down; and it’s sensible to imagine that humans with helminths would do the same. The tests take time, though, and Dr
Pritchard is proceeding cautiously.
But can the millions of sufferers wait? What happens in the age of instant gratification and global communication when a great, aching demand sniffs a ready supply? Type ‘helminthic therapy’ into
Google, and a parallel world of online hookworm experimentation unscrolls. It’s a world running in tandem with Pritchard’s, but not in an orderly fashion – no mice or permission from the
authorities. It’s a world as full of ecstatic, un-tested claims as Pritchard’s is cautious; one where communities cluster and agree, where dissent is heresy. This is hookworm not as science but as
All religions need a prophet, and in this case, there’s Jasper Lawrence – John the Baptist to David Pritchard’s reluctant messiah. Jasper was once one of those allergy sufferers for whom life is
only just worth the candle. He couldn’t leave his house in Santa Cruz during the spring; any contact with a cat made his eyes swell shut and his asthma left him struggling to breathe. To function
at all, Jasper was taking a steroid called Prednisone which turned him from a thin man into a sweating fatty, four stone overweight. By the time Jasper heard about helminthic therapy, his marriage
was breaking down and his five children were suffering.
Enter the worm. On a visit to Britain, Jasper heard David Pritchard on the radio. He began to read up on the hygiene hypothesis and suddenly inspiration struck: he wouldn’t sit around any more,
gaining weight and losing hope. He would set off to catch hookworms for himself.
Jasper’s journey began in Cameroon. He travelled to remote villages where he could be pretty sure that worms were in residence, trotted off to the cesspit area and had a good paddle around in bare
feet. What must the villagers have thought? After a fortnight or so, Jasper pulled up his socks and went home to wait for the result.
It came the following spring. Jasper’s usual allergies just failed to emerge. The worms were in evidence, and for the first time in his life the allergies were not. As the ultimate test he stroked
his (by now) ex-wife’s cat, which would usually have resulted in awful red weals. No problem.
So Jasper set up shop – harvesting his own hookworms and selling them to eager patients online (autoimmunetherapies.com in case you’re interested). Five years of ‘treatment’ for $3,900 – well, says
Jasper, you’d be paying 50 times that for any regular medicine. Patients travel to Europe to receive their worms, because the FDA have forbidden him from selling in the USA. He reports some
incredible successes – Crohn’s patients in seemingly permanent remission; asthmatics breathing freely, rheumatoid arthritis sufferers relieved. But he’s also a little paranoid.
‘Is this treatment approved by the medical authorities?’ asks someone on the website. Here is Jasper’s reply: ‘No. Given that drug companies do not have an incentive to replace expensive drugs with
the much cheaper helminthic therapy, there is no champion of this approach with the deep pockets required for evaluation by the FDA. So we do not anticipate approval.’ He has a point – but then, so
do the FDA.
Back in Nottingham, it’s Jasper who eventually rouses Dr Pritchard from his reverie. ‘Do you correspond with Jasper Lawrence?’ I ask. And at the mention of his name, Dr Pritchard starts, looks at
me anxiously. ‘No, I had to cut off contact with him,’ he says. ‘What he’s doing isn’t scientific. What people have to realise is that nothing is proven yet.’ But think of the mice tests, I say.
There’s definitely something in it. Pritchard smiles: ‘that’s what my colleagues keep saying: “Well David, there’s definitely something in it.” we’ll see,’ he says. ‘We’ll see.’ Then turns and
walks back to his worms.