The worm that turned
Professor David Pritchard is more than willing to get his hands dirty in the interests of science. After a long, hard field season studying hookworm infections in an island population in Papua New Guinea, he and his team returned to Nottingham to embark upon a brave experiment – infecting themselves with hookworm larvae and observing the effects.
‘The larvae are administered on a sticking plaster,’ he explains. ‘They go in through the skin then they travel to the lungs in the bloodstream, crawl up the airways and are swallowed. Within a few weeks they turn up in the gut.’
But while deliberately infecting themselves with worms may seem well beyond the call of duty, there is a very good reason why they did. Professor Pritchard and his team at Nottingham’s School of Pharmacy are about to begin the first ever clinical trial to test hookworms as a treatment for disorders of the immune system, including asthma and Crohn’s disease.
And who better to volunteer for the initial safety study than members of his own lab?
Professor Pritchard himself took 50. ‘They itch quite a bit when they go through your skin, but otherwise you don’t really notice them. It’s when they reach the gut that you realise they are present,’ he says. ‘It’s on this basis that we decided to lower the dosage to 10 worms for the trials.’
The trial follows research from as far back as the 1970s which suggests that people infected with hookworm – a parasitic worm that lives in the human gut – don’t seem to suffer from allergies like asthma. Today, the team’s research is sponsored by TheWellcome Trust, The National Asthma Campaign and the Medical Research Council.
‘If you look at the distribution of asthma worldwide it tends to be concentrated in the developed world,’ says Professor Pritchard. ‘Then if you superimpose a map of where hookworms are found, you’ll see that asthma and hookworms seem to be mutually exclusive.’
Similarly, Crohn’s disease seems to be a disease of the developed world. People living in Africa tend not to get Crohn’s disease, for example, whereas African American and African Europeans do. Perhaps, researchers have suggested, the lack of intestinal parasites in the developed world has left us more vulnerable to diseases like Crohn’s and asthma, caused by an overactive immune system.
Research by Dr Carsten Flohr, from the Division of Dermatology, Medical & Surgical Sciences at Nottingham should help make the picture clearer. Dr Flohr is currently working in Vietnam where he’s studying the links between parasitic worms and allergic diseases, including asthma and eczema.
‘Since April 2005, we’ve been conducting a large double blind placebo-controlled trial in a population of children in rural Vietnam to see whether de-worming treatment increases the risk of developing allergic diseases,’ says Dr Flohr. The results will be published in summer 2006, but in the meantime, Professor Pritchard and his team are pressing ahead with the second phase of their clinical trial.
The trial came about as a result of a simple epidemiological question. ‘We’ve been looking at hookworms for 20 years to try and find out how this worm can survive in the body. We wanted to know if these worms caused an immune response so we went to an island in New Guinea where a colleague from Oxford told us that hookworms were rife.’
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