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Point-of-care quantification of blood-borne filarial parasites with a mobile phone microscope

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Science Translational Medicine  06 May 2015:
Vol. 7, Issue 286, pp. 286re4
DOI: 10.1126/scitranslmed.aaa3480

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Dial “L” for Loa: Answering the call for mass drug administration

Filarial nematodes—tiny, parasitic worms that get into the bloodstream and use humans as hosts—are common in certain regions in Africa. One of these filarial nematodes, Loa loa, the causative agent of loiasis, is not compatible with current ivermectin-based mass drug administration (MDA) programs in the region, which are aimed to eliminate other worms that cause onchocerciasis and lymphatic filariasis. MDA causes severe and often fatal neurological side effects for patients co-infected with L. loa; thus, many MDA programs have been suspended. To resume these ivermectin-based campaigns, D’Ambrosio et al. devised a mobile phone–based strategy for quantifying Loa microfilariae in whole blood and, in turn, excluding those individuals from MDA.

The authors’ Loa-counting device comprised a mobile phone camera (as the video microscope) and a custom algorithm for tracking the “wriggling” motion of the microfilaria by quantifying the displacement of red blood cells surrounding the Loa. The entire device was packaged for point-of-care use, including its own “app” for smartphones. When tested on samples from 33 potentially Loa-infected subjects in Cameroon, Africa, the device was 94% specific (compared with microscopy results from thick blood smears) and 100% sensitive for patients about the threshold for severe adverse events (30,000 microfilaria per milliliter of blood). With its ease of use and only a fingerprick of blood, this mobile analytical device could be integrated into MDA programs, answering the call for safe and effective programs in Loa-endemic regions.