Hans Verhoef

Hans Verhoef

E-mail: Hans Verhoef

Publications

Background

I trained as a clinical epidemiologist, nutritionist and entomologist, and have a research interest in micronutrient malnutrition and infectious diseases. I also have an appointment as Senior Lecturer at the London School of Hygiene and Tropical Medicine, UK. Research on malaria has been a thread throughout my scientific career. I am particularly focused on the implementation of innovative, applied research that drives health policies and programmes in developing countries.

Based on a trial in rural Tanzania, my colleagues and I have recently shown that, contrary to expectations, zinc supplementation cannot play an important role in the control of malaria in African children. In this study, however, we found no support for the current recommendation by the World Health Organization (WHO) that iron supplementation is safe in children with iron deficiency: by contrast, our data suggested that particularly in these children, multi-nutrients including iron increased the frequency of malarial episodes by 40%.

In a trial among Kenyan school children, we have shown that daily consumption for 5 months of flour fortified with a new form of iron (i.e. ‘jacketed ’ as NaFeEDTA) reduced the prevalence of iron deficiency anaemia by 90%. Iron in the form that is widely used for fortification (‘elemental iron’) in many countries was ineffective. This study has contributed to the current WHO recommendation that flour should preferably be fortified with iron as NaFeEDTA; many African countries are now in the process of enacting legislation for mandatory fortification with this compound of industrially produced flour. Thus fortification with iron is rapidly becoming the only sustainable intervention that is being applied on a large scale to control iron deficiency anaemia in Africa.

In an earlier study, we reported on the effects of intermittent administration of anti-malarial drugs at therapeutic doses to control anaemia in young children. This idea has been further developed by a research consortium led by WHO, and forms the basis for a new, recently announced WHO strategy to control malaria in African children.

Before my scientific career, I was employed by WHO as a medical entomologist in the Solomon Islands to assist in the nation-wide control of malaria, and at its headquarters in Geneva, Switzerland, to develop research projects and policies on the links between agriculture, water use and vector-borne diseases, particulary in West Africa.

Current research interests

I am currently supporting two PhD fellows who are doing their research in rural Kenya. Martin Mwangi is conducting a randomised controlled trial in western Kenya to assess the effect of antenatal iron supplementation on Plasmodium infection in women at parturition. Most developing countries have national policies for antenatal iron supplementation; yet, there are many concerns about its safety in malaria-endemic areas. To prevent severe anaemia, all women in this study will receive iron fortificants in flour. We also use this trial as an opportunity to assess the feasibility of flour fortification in small-scale mills that serve rural communities.

Elise Talsma will be conducting a trial to assess the effect on vitamin A status of consuming provitamin A-rich cassava. This study is conducted in a dry area in eastern Kenya that is prone to food shortages. Enhancing the regular vitamin A supply through food-and agriculture-based approaches has the potential to reduce child mortality by 25%-50%. Conventional cassava varieties are white, and do not contain provitamin A. We collaborate with cassava breeders who have supplied us with selected varieties with a yellow colour that is due to high concentrations of provitamin A. Although there are questions about the bioavailability of provitamin A from various plant sources, we are hopeful that our work will lead to widespread distribution of genetically improved cassava varieties that farmers can grow indefinitely, without financial inputs, as a source of vitamin A.

Lastly, I am working with MSc students on innovative methods using flow cytometry to assess iron status in individuals with Plasmodium infection. This would be particularly useful because there is at present no diagnostic test available for this purpose.