NEW YORK (Reuters Health) – A newly developed assay that rapidly detects Zika virus and can be implemented in a mobile suitcase laboratory could facilitate testing of pregnant women in rural and low-resource settings, researchers say.
Dr. Ahmed Abd El Wahed of Georg-August-University in Goettingen, Lower Saxony, Germany, told Reuters Health, “Currently Dengue, Zika and Chikungunya viruses represent a global threat. The clinical picture of the three diseases is similar, and the same mosquito vector is involved in the transmission cycle.”
Figure: Zika virus Transmission Electron Micrograph (TEM).
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“Differentiating between them is of great importance,” he said by email, “as supportive treatment differs and the identification of any of the three viruses prompts implementation of control measures to avoid spreading an outbreak.”
As reported in PLOS Currents: Outbreaks, online January 25, Dr. El Wahed and colleagues developed an isothermal recombinase polymerase amplification assay (RTRPA), which they tested using 25 positive and nine negative urine samples collected during the Zika virus epidemic in Tuparetama, Brazil.
The RTRPA identified 23/25 positive (sensitivity, 92%) and 9/9 negative (specificity, 100%) samples. No cross reactivity was observed with Dengue, West Nile, Yellow Fever, tick-borne encephalitis, Japanese encephalitis, Rift Valley Fever and Chikungunya.
“The result was obtained in a maximum of 15 minutes,” Dr. El Wahed said. “Moreover, the assay . . . was implemented in a mobile suitcase laboratory (62x49x30 cm) containing all reagents and equipment for the detection of Zika, Dengue and Chikungunya viruses, and . . . operated by a solar-powered battery.”
“In developed countries, the mobile laboratory is useful for detecting cases in returning travelers at an airport or in quarantine, as well as in refugee camps,” he noted.
Dr. Daniel Caplivski, associate professor of infectious diseases at Icahn School of Medicine at Mount Sinai in New York City, commented, “The use of technologies that do not require thermal cycling for polymerase chain reactions is exciting because it allows for point-of-care diagnosis. This is particularly exciting because the performance of the assay was excellent, and the reported turnaround time of 15 minutes allows for point-of-care decision making and counseling.”
“The use of similar assays for Dengue and Chikungunya viruses makes the test particularly practical since the clinical presentation and epidemiological overlap makes it very difficult to distinguish among these vector-borne infections,” he told Reuters Health by email.
“There are some limits to the assay, as the time in which the virus is detectable via molecular methods in the blood or the urine remains limited,” Dr. Caplivski noted. “Serologic assays will likely still be necessary for certain patients to further exclude Zika virus infection.”
Two coauthors of the study are employed by Tib MolBiol, a manufacturer of oligonucleotides.
SOURCE: Abd El Wahed A, Sanabani SS, Faye O, Pessôa R, Patriota JV, Giorgi RR, Patel P, Böhlken-Fascher S, Landt O, Niedrig M, Zanotto PMdA, Czerny CP, Sall AA, Weidmann M. Rapid Molecular Detection of Zika Virus in Acute-Phase Urine Samples Using the Recombinase Polymerase Amplification Assay. PLOS Currents Outbreaks. 2017 Jan 25 . Edition 1. doi: 10.1371/currents.outbreaks.a7f1db2c7d66c3fc0ea0a774305d319e.