The mosquito species Aedes aegypti is estimated to infect about 100 million people annually with devastating illnesses such as dengue and zika. Originally thought to affect only tropical regions, mosquito-transmitted viruses are increasingly becoming a worldwide health challenge due to increased global movement and insecticide resistance. One approach to reduce the spread of diseases like chikungunya, dengue and zika is to target mosquitoes and infect them with Wolbachia.
Previously, it was difficult to check if A. aegypti mosquitoes were infected with Wolbachia: mosquitoes show no visual symptoms, and current diagnostic tests are costly and hard to read. However, in a new PLOS Neglected Tropical Diseases study, Sanchita Bhadra of the University of Texas in Austin and colleagues describe their new diagnostic tool that will aid research “in the field.” Their new tool uses a cellphone camera and app to identify the mosquito’s species and if it is carrying Wolbachia.
The researchers combined fluorescent probes for A. aegpyti DNA and Wolbachia DNA with a LAMP assay, a simple, popular DNA detection test. When the target DNA is present, the probes bind to it and produce what the researchers deem a “yes/no” fluorescence which is detectable by a cellphone camera.
In a blinded test of 90 field-caught mosquitoes, the researchers demonstrated very high specificity and sensitivity in identifying both Ae. aegypti mosquitoes and Wolbachia-infected mosquitoes with their new cellphone tool. The researchers’ new test prevents false positive results (a common drawback of LAMP) and yields an accurate yes/no visual read out on the smartphone instead of relying on a subtle variation of color. It can also directly analyze ground mosquitoes without requiring nucleic acid purification or cold storage, making it potentially invaluable “in the field.”
The researchers conclude: “We are currently automating the assays and workflow on low-cost paper and plastic devices that will not only further streamline diagnostic application but will also provide sealed chambers for biohazard and aerosol containment for macerating mosquitoes.”
Citation: Bhadra S, Riedel TE, Saldaña MA, Hegde S, Pederson N, et al. (2018) Direct nucleic acid analysis of mosquitoes for high fidelity species identification and detection of Wolbachia using a cellphone. PLOS Neglected Tropical Diseases 12(8): e0006671. https://doi.org/10.1371/journal.pntd.0006671
Image Caption: “Aedes aegypti” (freeimage4life, Flickr, 2013)