Photo by Gabrielle Tenenbaum
Progress in reducing the malaria burden in Africa may have had the paradoxical effect of increasing malaria transmission among older children in recent years, according to research published in PLOS Medicine.
Researchers analyzed data on children admitted to a hospital in Kenya over a 25-year period and found that malaria transmission decreased from 1998 to 2009 but began to rise after that, and older children accounted for most of this increase.
The researchers believe this may be a result of a decrease in acquired immunity among the older children.
Philip Bejon, PhD, of the University of Oxford in the UK, and his colleagues conducted this study. The team analyzed malaria screening data from pediatric emergency admissions to Kilifi County Hospital between 1990 and 2014 and linked it to data on residence and insecticide-treated bednet (ITN) use.
During the period studied, 69,104 children, ages 3 months to 13 years, had malaria screening data available.
The proportion of hospital admissions found positive for malaria decreased from a high of 56% in 1998 to a low of 7% in 2009, but then rose again to 24% in 2014.
The researchers said they were unable to determine the cause of the decline in malaria infections between 1998 and 2009, which pre-dated the dramatic scale-up in ITN distribution and use in the area.
However, they noted that the subsequent increases in malaria infections coincided with a shift in burden from younger to older children, and children who lived in areas with high usage of ITNs were less likely to present with malaria than children who lived in areas with low usage of ITNs.
The researchers said the upswing in malaria transmission among older children following a period of low malaria transmission may be due to decreased acquired immunity because these children were less likely to have been exposed to malaria early in life.
The team also noted that varying levels of access to care and ITN use may have introduced bias in this study, and these data were taken from a single geographic setting. However, they still believe the findings suggest malaria elimination will require continued—and increasing—vigilance.
