Sickle-cell study boosts call for improved childhood immunisation programmes in Africa
10 September 2009
Sickle-cell anaemia affects millions of people worldwide, but more than 80 per cent of cases are in Africa, where 200 000 children are born with the disease every year. It is a genetic disease, which leads to the formation of sickle-shaped red blood cells. These cells do not pass easily through blood vessels and can form clusters that block the flow of blood to limbs and organs, leading to pain, serious infections and organ damage.
Despite the huge number of children who are born with sickle-cell anaemia in Africa annually, the diagnosis is often delayed and 90 per cent of these children die before the disease is ever diagnosed. It has long been assumed that severe infections are responsible for many of these deaths, but this has never been properly investigated.
To find out the scale of the problem in Africa, researchers at the Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme in Kilifi, on the coast of Kenya, studied blood samples from all children aged under 14 who were admitted to the local hospital during the ten-year period 1998-2008. They screened for cases of bacteraemia (bacterial infections of the blood) and then tested the positive samples for sickle-cell anaemia.
By screening almost 40 000 admissions to the hospital, the researchers identified more than 2000 cases of bacteraemia. However, while in the general population fewer than three in 1000 children were found to have sickle-cell anaemia, this figure increased more than 20-fold - to over 60 per 1000 - for children admitted to hospital with bacteraemia, confirming that, as in the developed world, African children with sickle-cell anaemia are at huge risk of bacteraemia.
Amongst the most common causes of bacteraemia among children with sickle-cell anaemia were 'Streptococcus pneumoniae' (accounting for 41 per cent of cases) and 'Haemophilus influenzae' type b (12 per cent of cases), both of which are serious infections that may lead to pneumonia or meningitis, but are preventable by vaccination.
The research was led by Dr Tom Williams, a Wellcome Trust Senior Fellow and Reader in Tropical Medicine at the University of Oxford. He commented: "Our study provides strong impetus for the introduction of vaccination programmes for all children in Africa, a move that will dramatically improve the survival chances of children born with sickle-cell anaemia. Health policies need to be based on solid evidence such as this research, rather than on rumour and personal preference."
The researchers estimate that in Kilifi, it is likely that up to one quarter of all child deaths are attributable to sickle-cell anaemia, with bacterial infections accounting for a sizable proportion.
Developing countries are working to reduce childhood mortality to meet one of the Millennium Development Goals. However, the focus is on the major causes of mortality - more than 70 per cent of child deaths every year are attributable to six causes: diarrhoea, malaria, neonatal infection, pneumonia, preterm delivery or lack of oxygen at birth. As childhood mortality falls, Dr Williams believes that the relative contribution of sickle-cell anaemia will increase without the development and implementation of specific interventions.
"To date, sickle-cell anaemia has not enjoyed a high priority on African health agendas, despite the relatively high impact it has on childhood mortality, which far exceeds estimates for HIV," he says. "HIV commands vast attention from the international community, yet sickle-cell anaemia is virtually invisible on the international health agenda."
Image: Sickle-cell anaemia. Credit: EM Unit, UCL Medical School, Royal Free Campus, Wellcome Images
Reference
Williams TN et al. Bacteraemia in Kenyan children with sickle-cell anaemia. Lancet 2009.
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Notes for editors
The Wellcome Trust is the largest charity in the UK. It funds innovative biomedical research, in the UK and internationally, spending over £600 million each year to support the brightest scientists with the best ideas. The Wellcome Trust supports public debate about biomedical research and its impact on health and wellbeing.
The Kenya Medical Research Institute (KEMRI) is a Kenya government parastatal with the responsibility for health research to improve the health of Kenyans. It is one of the most well developed national research institutes in Africa with a network of centres across Kenya.
The University of Oxford’s Medical Sciences Division is one of the largest biomedical research centres in Europe. It represents almost one-third of the University of Oxford's income and expenditure, and two-thirds of its external research income. Oxford's world-renowned global health programme is a leader in the fight against infectious diseases (such as malaria, HIV/AIDS, tuberculosis and avian flu) and other prevalent diseases (such as cancer, stroke, heart disease and diabetes). Key to its success is a long-standing network of dedicated Wellcome Trust-funded research units in Asia (Thailand, Laos and Vietnam) and Kenya, and work at the MRC Unit in the Gambia. Long-term studies of patients around the world are supported by basic science at Oxford and have led to many exciting developments, including potential vaccines for tuberculosis, malaria and HIV, which are in clinical trials.