Malaria risk at home

Some young children suffer twice as many malaria attacks as those who may be living just yards away from them, new research reveals today.

A five-year study of over 3500 children living in eastern Kenya shows that household conditions can play a major role in susceptibility to the disease, which kills around 2m people every year.

And although some of this is explained by families who live together sharing some malaria-resistant genes, the biggest impact seems to come from household conditions. Even the well-known resistance gene, sickle cell, contributes just a small amount to malaria risk.

Dr Margaret Mackinnon, who carried out the study while at the University of Edinburgh along with colleagues working for the Kenya Medical Research Institute/Wellcome Trust Programme in Kilifi, said: "It's quite remarkable to see the big variation in cases of malaria among children living almost side by side. Some suffered twice the amount of infections as those they played and even ate with.

"In this study we teased apart how much this was due to sharing genes versus sharing the same house. It turns out that living in the same home is more important than having the same genes.

"We don't yet know exactly what makes the difference between a good or a bad house. But a lot probably depends on whether there is a mosquito-breeding site in the back yard, the quality of the building and whether insecticides or other repellents are used. Identifying and improving factors that put some homes at much lower risk than others would go a long way towards relieving the burden of disease in children living under such conditions.

"Eventually studies of the malaria resistance genes may bring us new drugs or vaccines but until then it would seem a better option is to concentrate on making sure homes carry less of a risk."

The study, which is published online by the Public Library of Science, Medicine, today (8 November), was split in two. The first investigation involved cases of mild malaria among 640 under-tens who lived in 77 households. Each of these consisted of between three and six houses - which are home to various family members- clustered together.

Among this cohort it was found that inherited genes were responsible for the variation in malaria fevers in 24% of cases with 29% being due to household conditions.

The researchers also looked at a second group of 2900 under- fives. Around 1000 of these were admitted to hospital at least once, with half suffering from malaria.

The study gathered information on genetic relationships between children, parents and sometimes grandparents and concluded that while resistance is passed on through generations what really counts is whether they live in a malarious house.

The Wellcome Trust is an independent research-funding charity established in 1936 under the will of tropical medicine pioneer Sir Henry Wellcome.The Trust's mission is to promote research with the aim of improving human and animal health and it currently spends more than £400m p.a.