Researchers have created a field-applicable, ultrasensitive diagnostic assay that specifically detects DNA sequences from all Plasmodium species in both symptomatic and asymptomatic malaria.
Malaria has a massive global impact. According to estimates, 228 million cases and 405,000 subsequent deaths occurred in 2018. During 2007, the World Health Organisation (WHO) supported the ambitious goal of eradicating malaria. However, since 2014, the decline has stalled and, in some regions, reversed. Asymptomatic carriers of Plasmodium parasites hamper malaria control strategies. To achieve eradication, ultrasensitive diagnostics for low parasite density infections (<100 parasites per microlitre of blood) that are applicable in resource-limited settings are essential. The current gold standard for distinguishing between Plasmodium species is light microscopy. Nonetheless, this method is time-intensive and requires skilled technician interpretation.
Nira Pollock, Associate Medical Director of Boston Children’s Hospital’s Infectious Diseases Diagnostic Laboratory and Associate Professor of Pathology and Medicine at Harvard Medical School, stated:
“Unfortunately, available rapid diagnostic approaches cannot distinguish all four Plasmodium species from one other, which can be important to initiate the definitive course of treatment, and, most importantly, they are ineffective for detecting low numbers of Plasmodium parasites in asymptomatic individuals.”
Field-applicable, ultrasensitive diagnostic tool
In a study, published in PNAS, a team of multi-disciplinary scientists developed a field-applicable, ultrasensitive malaria diagnostic tool. This comprised of a 10-minute sample preparation step and a 60-minute platform SHERLOCK assay (CRISPR-base nucleic acid detection).
The team showed that these assays can specifically detect below two parasites per microlitre of blood. WHO consider this level of detection to be a “significant improvement on expert microscopy”. Furthermore, the researchers found that the assays could call samples containing P. falciparum and P. vivax species with 100% sensitivity and specificity. The assay is also designed to detect the presence of frequently mutated P. falciparum strains that have lost their HRP2 antigen. These strains often escape detection by traditional diagnostic tests.
James Collins, Wyss Founding Core Faculty member, stated:
“This field-ready SHERLOCK diagnostic malaria assay surpasses the sensitivity and specificity requirements set by the WHO for a desired test that can be used to detect low parasite density in asymptomatic carriers of all major Plasmodium species.
Its highly streamlined design could provide a viable solution to the present diagnostic bottleneck on the path to eliminate malaria, and more generally enable malaria surveillance in low-resource settings.”
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