Bloodlines: sickle cell disease in Tanzania

In 2004 Dr Julie Makani, Clinical Research Fellow of Oxford's Nuffield Department of Medicine, began a project on sickle cell disease at Muhimbili University in Dar Es Salaam, in association with the KEMRI-Wellcome Trust Research Programme in Kenya. 'From a scientific point of view, sickle cell disease is a really good model', she says, 'because one gene causes the disorder, yet patients can have mild, moderate or severe disease. You have an opportunity to try to understand the genetics as well as the environmental factors that influence of the severity of disease.'

Sickle cell disease (SCD) persists in populations where malaria is endemic, because people who inherit only one copy of the faulty gene gain some protection against malaria. Those with two copies suffer a severe form of anaemia, are more susceptible to infection, and can suffer strokes as their diseased red blood cells block small vessels in the brain.

Dr Makani expected to gather a cohort of around 400 children for her study. Today the Wellcome-Muhimbili Programme is following 2,500, one of the largest single-centre cohorts of children with SCD in the world. Tanzania has one of the highest rates of the disease in Africa, with 8,000–11,000 children a year affected. 'We don't have newborn screening programmes and therefore most children don't know that they have the disease,' says Dr Makani. The programme integrates research into the provision of health care for affected children, many of whom would otherwise die in childhood.

One research project is designed to test the safety and efficacy of the drug hydroxyurea in patients with sickle cell disease. The drug works by raising haemoglobin levels, so patients have less anaemia. In developed countries, anaemia is often treated with blood transfusions. 'This is not really an option for us, because too little blood is available and because of the risks and complications due to blood transfusion,' says Dr Makani, 'so we really need to explore how hydroxyurea can make an impact in our setting.' The drug itself is not without risks, however. 'It reduces the white blood cell count, and therefore there is an increased risk of bacterial infection; it may also be associated with an increased risk of malaria. We want to do a clinical trial to see if it is safe to use in Tanzania.'

The programme also funds Dr Sharon Cox (from the London School of Hygeine and Tropcial Medicine) to study nutritional aspects of the care of SCD patients, and Oxford's Professor Charles Newton has moved from the KEMRI-Wellcome Research Programme in Kenya to work on the neurological complications of the disease. The expanding research programme at Muhimbili University has provided a focus for scientists working on the disease across Central Africa. In 2009 they formed the Sickle Cell Disease Research Network of Central Africa (REDAC), which meets annually to share resources, experience and expertise: the 2012 meeting took place in Tanzania in June.

While a cure for sickle cell disease is not in sight, early diagnosis and good care can cut most deaths in childhood. The Muhimbili-Wellcome Programme a step towards achieving that aim for children in Tanzania and beyond.