Malaria Diagnosed from Drop of Blood or Saliva

Scientists have developed a new method for diagnosing malaria based on measuring the activity of an enzyme called topoisomerase I from the Plasmodium parasite.

The technology on which the method is based is called Rolling Circle-Enhanced Enzyme Activity Detection (REEAD), which makes it possible to diagnose malaria from a single drop of blood or saliva. This method is more time-effective and cost-effective than current diagnostic methods, and can be performed by personnel who have no specialized training. It can therefore be used in low-resource areas without the use of expensive equipment, clean water, or electricity.

The REEAD-based method distinguishes itself from other quick-test methods because it can measure whether a given Plasmodium infection is resistant to drugs. The newly developed technology is also the only quick-test method that makes it possible to diagnose the less common malaria parasites (P. ovale, P. knowlesi and P. malariae) in addition to the most common Plasmodium parasites (P. falciparum and P. vivax).

The high sensitivity is achieved by performing the REEAD technology within droplets surrounded by oil. The malaria parasites are distributed in the picoliter droplet, where they react effectively with the other components of the REEAD technology. The new method amplifies the signal from the malaria parasites since each parasite can give rise to more DNA molecules using the REEAD technology. Under the microscope, each DNA product is seen as a red dot.

The sensitivity, combined with its ability to detect infection in very small samples of blood or saliva, makes the method suitable for large-scale screening projects. This is of great importance in areas where the disease is close to being eradicated, and where it is therefore essential to identify and treat all patients infected with one of the above-mentioned parasites–even those who do not show symptoms of the disease.

Scientists who developed this method were led by Associate Professor Birgitta Knudsen, who is affiliated with the Interdisciplinary Nanoscience Centre (iNANO) and the Department of Molecular Biology and Genetics, Aarhus University (Denmark). Colleagues from Denmark (Department of Pathology and Department of Clinical Medicine, Aarhus University Hospital) and abroad (Duke University, University of Rome, University of St Andrews and University of Lyon) contributed to this project.

“This combination of molecular biologists, doctors, engineers, and statisticians has been important for our success in developing the new method,” said Prof. Knudsen.

The study was published in the November 2, 2012, edition of ACS Nano.

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