According to the World Health Organization, more than 500,000 people die each year from malaria, a disease that is transmitted by mosquitoes in the genus Anopheles. In addition to the half a million deaths, about 200 million people are infected annually.
Now researchers at Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Australian National University are working on tests for diagnosing malaria by identifying distinctive chemicals that can be detected in the breath of patients infected with the disease.
They looked at the breath of volunteers, who had been given a controlled malaria infection as part of existing studies to develop new treatments, and they found that the levels of some normally almost-undetectable chemicals increased markedly in the breath of the volunteers during the malaria infection.
“What is exciting is that the increase in these chemicals were present at very early stages of infection, when many other methods would have been unable to detect the parasite in the body of people infected with malaria,” said Dr. Stephen Trowell, research group leader at CSIRO. “In addition to its potentially better sensitivity, human breath offers an attractive alternative to blood tests for diagnosing malaria.”
The CSIRO scientists published an article about the new test in the Journal of Infectious Diseases. Their research involved two independent studies where experimental drug treatments were being tested in volunteers who had been given a very small dose of infection.
Using a sophisticated analytical instrument, the researchers identified four sulphur-containing compounds whose levels varied across the time course of the malaria infection.
“The sulphur-containing chemicals had not previously been associated with any disease, and their concentrations changed in a consistent pattern over the course of the malaria infection,” said co-author Dr. James McCarthy. “Their levels were correlated with the severity of the infection and effectively disappeared after they were cured. Malaria continues to place a huge health and economic burden on many of the poorest people in the world.”
In an interesting twist, the researchers detected foul-smelling compounds — albeit at levels far too low for humans to smell — in the breath of people with malaria.
Until now, these chemicals have only been detected using very expensive, laboratory-based instruments, and only in the breath of volunteers experiencing a controlled malaria infection in the clinic.
“Now we are collaborating with researchers in regions where malaria is endemic, to test whether the same chemicals can be found in the breath of patients,” Dr. Trowell said. “We are also working with colleagues to develop very specific, sensitive, and cheap ‘biosensors’ that could be used in the clinic and the field to test breath for malaria.”
Currently, malaria diagnosis remains mostly based on using powerful microscopes to look for parasites in blood using a method discovered in 1880. As the world starts to work towards the elimination of malaria, there is an urgent need for more sensitive and convenient tests to detect early and hidden cases.
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