JOHANNESBURG - The retina in the eye of patients with cerebral malaria has provided scientists with vital clues into why it is so deadly.
One of the world's biggest killers, malaria claims over a million lives every year, mainly children and pregnant women in Africa, and adults in southeast Asia.
It has been known that cerebral malaria is accompanied by changes in the retina, known as malarial retinopathy, which can be seen by examining the eye.
Because the retina can be considered an extension of the central nervous system, it has been used previously as a 'window into the brain', allowing swifter diagnosis of cerebral malaria.
However, until now it was not clearly understood why the disease should be so deadly.
Researchers in Malawi have shown for the first time in patients that the build-up of infected blood cells in the narrow blood vessels of the brain causes a potentially lethal lack of oxygen to the brain.
Malaria parasites enter the bloodstream from bites by infected mosquitoes and live in red blood cells, making them stick to the inside of narrow blood vessels and causing blockages.
Most deaths occur as a result of cerebral malaria, where red blood cells infected by malaria parasites build up into the brain, leading to coma and convulsions and, if not treated swiftly, death.
In new research, Nick Beare of the Royal Liverpool University Hospital, with colleagues at the Queen Elizabeth Central Hospital in Blantyre, Malawi, examined the retinas of 34 children admitted to the hospital with cerebral malaria.
They used a technique known as fluorescein angiography, which involves injecting a special dye into the arm intravenously and photographing its passage through the blood vessels of the retina.
It is used to identify fluid leakage or blockages in the small blood vessels at the back of the eye. More than four in five of the children examined by Beare and colleagues were found to have impaired blood flow in the blood vessels of their eyes.
Three-quarters had whitening to areas of the retina where blood did not appear to reach, implying that the parasites were disrupting the supply of oxygen and nutrients.
'We have previously used the retina to accurately diagnose severe malaria, but now this window into the brain has opened up our knowledge of what makes cerebral malaria so deadly,' said Beare.
'This is the first study to clearly show impaired blood flow in the eyes of patients with cerebral malaria, according to Royal Liverpool release.
These findings were published in the Journal of Infectious Diseases.
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