A phone pressed to a microscope, and the parasite counts itself

In a parasitology laboratory in Cochabamba, Mary Cruz Torrico and colleagues in Spain built a diagnostic tool from parts a rural clinic already owns: an ordinary microscope, a smartphone, and a small 3D-printed collar to hold one against the other. The software counts Trypanosoma cruzi in about 350 milliseconds, offline. In Bolivia, where roughly one person in sixteen carries the parasite, that matters more than anywhere.

The device her team tested with researchers from Spain's Instituto de Salud Carlos III, the Universidad Politécnica de Madrid, the company SpotLab, CIBER-ISCIII and Fundación Mundo Sano changes the second half of that sentence, not the first. The phone's camera photographs the sample through the eyepiece; a model running on the handset itself, with no internet connection, finds and counts the parasites. Tested on human blood and cerebrospinal fluid collected in Bolivia, plus animal-model specimens, it reached about 86% accuracy. In a pilot laboratory run, a single operator working with the phone setup detected more than 96% of the parasites present.

Microscopy only works in narrow windows — the acute phase, roughly the first eight to twelve weeks after infection, and in newborns of infected mothers. Those windows are exactly when treatment works best, and exactly where the rural clinics are.

The disease carries a physician's name because of a similar act of looking. In 1909, at Lassance in Minas Gerais, Carlos Chagas found flagellates in the hindgut of triatomine bugs, sent them to Rio de Janeiro, and then went looking for the illness they might cause. He found it in a two-year-old girl, Berenice Soares de Moura. She was followed by researchers for the rest of her life and died in 1981.

More than a century on, treatment still rests on two drugs from the 1960s and 1970s, benznidazole and nifurtimox, each demanding a 60-day course with frequent side effects. Neither is much use to someone who was never diagnosed.

ISCIII's María Flores-Chavez and UPM's María Jesús Ledesma say the work now is to move the system out of the pages of PLOS Neglected Tropical Diseases and into clinics — and possibly to adapt it to other parasitic diseases. SpotLab's platform has already been turned on malaria, tuberculosis and soil-transmitted helminths.

The adapter is a piece of printed plastic. The microscope is the one already on the bench.