[NAIROBI] A dramatic drop in the rates of severe childhood malaria in some regions of Kenya is posing new medical challenges as people in high-risk regions lose their immunity and transmission patterns alter, according to researchers.
An analysis of data collected over 18 years from malaria-infected children at Kilifi District Hospital, on Kenya's Indian Ocean coast, found that paediatric admissions for malaria had fallen by 75 per cent over a period of just five years.
The data echo results from many other malaria-prone regions of Kenya, and the entire coastline of the east of the country, according to co-author Norbert Peshu, director of the Centre for Geographic Medicine Research - Coast at the Kenya Medical Research Institute (KEMRI).
The authors believe a major contributor to the drop in infections was the replacement of chloroquine with sulfadoxine-pyrimethamine. Other interventions including the use of insecticide-treated bednets and artemisinin-based therapies could have contributed, they say, but the surge in their use came after the steep fall in transmission of the disease.
The KEMRI data, published in The Lancet this month (1 November), suggest that it is not until malaria parasites are infecting less than 20 per cent of the population that the incidence of the disease falls — and that the fall is then a sharp one.
Shahnaaz Sharif, Kenya's acting director of public health and sanitation, warns that improvements in malaria infection rates commit governments to continued control and treatment, saying a resurgence of malaria would be ''devastating'' in communities that have lost their previous levels of immunity.
An example of an at-risk group is children above the age of five. Malaria infection above this age is more likely to lead to cerebral malaria, which has a worse prognosis than the severe malarial anaemia that afflicts younger children.
"Older children exposed to higher levels of transmission in early life might have a lower incidence of cerebral malaria than those who grew up in an area of low, stable endemicity," say the authors.
"We need continued vigilance and emphasis on insecticide-treated nets, early treatment and other control measures to win the war against malaria," Sharif told SciDev.Net.
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The Lancet 372, 1555 (2008)