Tropical medicine could get a big boost in the near future from the development of a new handheld device that allows for the rapid detection of blood-borne parasites. Using an iPhone's camera plugged into a 3D-printed microscope base, doctors can now test a blood sample for the presence of the parasitic worm Loa loa within minutes, according to a study published in Science Translational Medicine. This process typically demands lab equipment and over a day to complete, but the new CellScope Loa reduces both requirements by being portable, fast, and automated.

Loa loa has proven a major stumbling block for the treatment of two other parasitic diseases: river blindness and elephantiasis. Though drug treatment programs were initiated to help treat those infections in Central Africa — where they are most prevalent — those programs were halted because Loa loa infection led to serious side effects. People infected with Loa loa and receiving drugs for river blindness and elephantiasis suffered brain damage; some died. Being able to quickly and reliably test for Loa loa may be key in resuming the treatment programs to help fight other parasitic diseases.

The CellScope Loa is the product of collaboration between scientists at the University of California-Berkeley, and the US National Institute of Allergy and Infectious Diseases. It works by capturing video of a blood sample and looking for the characteristic "wriggling" motion of Loa loa microfilaria. Motion detection simplifies things dramatically, as the blood doesn't require any special preparation before being tested, and an associated iPhone app reduces the rate of human error by automating the entire process. Once the health care worker activates the scan, their iPhone uses a Bluetooth connection to control gears inside the base of the scope, moving the sample in front of the camera. An algorithm then analyzes the footage and provides a worm count. All within the space of a couple of minutes.

The researchers are confident in the accuracy of their new system, which they claim has a false-negative error rate as low as one in 10 million. That's the more important type of error to reduce, given that the goal is to "test and not treat" patients who have Loa loa infections; they're looking to ascertain that people won't suffer damaging side effects when receiving treatment for river blindness or elephantiasis. An initial field test on 33 potentially Loa loa-infected subjects in Cameroon has shown the CellScope producing comparable results to those obtained in a lab. There were no false negatives and only two false positives. With such encouraging early results, the study is now being expanded to about 40,000 people in the country.

"The availability of a point-of-care test prior to drug treatment is a major advance in the control of these debilitating diseases," says Berkeley ecologist Vincent Resh, who isn't part of the research team but has worked on the control of river blindness in West Africa for 15 years. "The research offering a phone-based app is ingenious, practical, and highly needed."