Vietnam study probes the role of gut worms in allergies

Gut parasites, such as hookworm, have evolved together with their human hosts for millions of years. Over time, these parasites have developed ways of surviving in the human gut by 'turning down' the immune response directed against them, prolonging their survival inside the host.

This reduction in immune response may also have the effect of reducing allergic tissue reactions that characterise asthma and other allergic conditions.

The latest study in this area of research is led by Dr Carsten Flohr, a clinical scientist from The University of Nottingham and Dr Luc Nguyen Tuyen, from the Khanh Hoa Provincial Health Service in central Vietnam. This work was supported through research grants from Asthma UK, the Bastow Award from the Special Trustees for Nottingham University Hospitals and a Fellowship from University College, University of Oxford.

Dr Flohr has examined the links between worms and allergic diseases in Vietnamese children and found that those with the highest level of hookworm infestation were the least likely to have an allergic response to house dust mites.

These findings support the hypothesis that gastrointestinal infection with either hookworms or other micro-organisms protects against allergy and add further weight to the so-called ‘hygiene hypothesis’.

Dr Lyn Smurthwaite, Research Development Manager for Asthma UK said: “The ‘hygiene hypothesis’ suggests that high rates of allergies and asthma in developed countries are a result of our immune systems becoming unbalanced due to improved sanitation and hygienic lifestyles that no longer expose us to the same array of bacteria, viruses or parasites. We look forward to future results in this area.”

The study involved 1,600 children aged six to 18, in four neighbouring rural communities in Khanh Hoa province, central Vietnam. Their lifestyles were studied, along with their sensitivity to common allergens and their level of infestation with hookworm and other parasites.

Following on from the study just reported online in the Journal of Allergy and Clinical Immunology, Dr Flohr and his colleagues in Vietnam have conducted an intervention study in the same population during which they regularly de-wormed schoolchildren to see whether this increased the prevalence of allergic diseases. This second study is now coming to a close and the results will be published early next year.

Dr Flohr said: “The results from such an intervention study will allow us to draw firmer conclusions as to whether gut worm infestation truly protects against allergic disease and sensitisation.”

Co-applicants on the Asthma UK research grant that is funding the work were Professors John Britton, David Pritchard, and Hywel Williams. The Nottingham team is collaborating with researchers from the Wellcome Trust Major Overseas Programme at the Oxford University Clinical Research Unit Hospital for Tropical Diseases in Ho Chi Minh City, where Dr Flohr has been based for his field work.

The University of Nottingham is leading the way in the investigation of links between hookworm infestation — or lack of it — and human illness. Two further currently ongoing trials are looking at the possibility that hookworm infection may alleviate symptoms of hay fever and Crohn’s Disease.

If these studies show positive results, future drugs that mimic the immunological effects of hookworm infection could provide promising therapeutic options for patients with allergic and other autoimmune diseases.