Scientists from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, and the University of California, Berkeley, and colleagues have developed a mobile phone microscope to measure blood levels of the parasitic filarial worm Loa loa.
The point-of-care device may enable safe resumption of mass drug administration campaigns to eradicate the parasitic diseases onchocerciasis (river blindness) and lymphatic filariasis (elephantiasis).
Efforts to eliminate these diseases in Central Africa through community-wide administration of antiparasitic drugs have been suspended due to potentially fatal drug-associated side effects in people with high blood levels of Loa microfilariae, the filarial worm’s larval form. A potential solution is to identify and exclude such people from mass drug administration. However, standard methods for measuring microfilariae are time-consuming and must be performed by trained personnel with laboratory equipment.
To rapidly screen for Loa infections in community settings, the scientists developed CellScope Loa, a video microscope integrating an Apple iPhone 5s. With the help of a custom iPhone app, the device automatically captures and analyzes videos of the characteristic “wriggling” motion of microfilariae, enabling quantification of microfilariae in blood from a finger prick in less than two minutes. No special preparation of the blood is required, limiting potential error and sample loss, and healthcare workers need minimal training to use the automated device.
Screening of blood samples from potentially Loa-infected people under field conditions in Cameroon, Africa, showed that CellScope Loa results correspond well to those obtained by standard methods, correctly identifying people with microfilarial levels over a certain threshold. Although additional work is needed to prepare the technology for broad use, the researchers predict that a team of three workers could screen up to 200 people during the four-hour midday window when Loa circulates at its peak in the blood.