Researchers have developed two tests that can discern within three days whether the malaria parasites in a given patient will be resistant or susceptible to artemisinin, the key drug used to treat malaria. The tests were developed by researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, working with French and Cambodian colleagues in Cambodia. They offer a more rapid, less costly advantage over current drug-responsiveness tests, which require malaria patients to be hospitalized for blood draws every six hours over the course of several days. In both tests, young parasites are briefly exposed to a high dose of artemisinin, mimicking the way parasites are exposed to the drug in people being treated for malaria, and their survival is measured 72 hours later.
The first test is conducted on blood taken from a malaria patient at the same time as the first dose of artemisinin-based combination drug therapy is administered. The test returns results in 72 hours and can predict whether the patient has slow-clearing, drug-resistant parasites. The researchers note that the simple, new test could be used for surveillance studies to monitor and map the emergence or spread of artemisinin-resistant malaria parasites. In the current study, researchers using this test detected artemisinin-resistant parasites at sites in Northern and Eastern Cambodia for the first time.
The second test is conducted on parasites grown in the laboratory. This test requires trained technicians to adapt parasites from a malaria patient to a laboratory culture, synchronize the life-stages of the parasites, and then apply the drug only to those that are three hours old or younger. This test will likely be most useful in future studies designed to elucidate the molecular basis of artemisinin resistance and to screen new malaria drugs.
The study was led by Rick Fairhurst, M.D., Ph.D., of the NIAID Laboratory of Malaria and Vector Research, and Didier Menard, Ph.D., of the Institut Pasteur du Cambodge, Cambodia.
B Witkowski et al. Novel phenotypic assays for the detection of artemisinin-resistant Plasmodium falciparum malaria in Cambodia: in-vitro and ex-vivo drug-response studies. The Lancet Infectious Diseases DOI: 10.1016/S1473-3099(13)70252-4 (2013).
NIAID Director Anthony S. Fauci, M.D., and Rick M. Fairhurst, M.D., Ph.D., Laboratory of Malaria and Vector Research, NIAID, are available to discuss this research.
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