title: Point-of-care quantification of blood-borne filarial parasites with a mobile phone microscope.
abstract: Parasitic helminths cause debilitating diseases that affect millions of people in primarily low-resource settings. Efforts to eliminate onchocerciasis and lymphatic filariasis in Central Africa through mass drug administration have been suspended because of ivermectin-associated serious adverse events, including death, in patients infected with the filarial parasite Loa loa. To safely administer ivermectin for onchocerciasis or lymphatic filariasis in regions co-endemic with L. loa, a strategy termed "test and (not) treat" has been proposed whereby those with high levels of L. loa microfilariae (>30,000/ml) that put them at risk for life-threatening serious adverse events are identified and excluded from mass drug administration. To enable this, we developed a mobile phone-based video microscope that automatically quantifies L. loa microfilariae in whole blood loaded directly into a small glass capillary from a fingerprick without the need for conventional sample preparation or staining. This point-of-care device automatically captures and analyzes videos of microfilarial motion in whole blood using motorized sample scanning and onboard motion detection, minimizing input from health care workers and providing a quantification of microfilariae per milliliter of whole blood in under 2 min. To validate performance and usability of the mobile phone microscope, we tested 33 potentially Loa-infected patients in Cameroon and confirmed that automated counts correlated with manual thick smear counts (94% specificity; 100% sensitivity). Use of this technology to exclude patients from ivermectin-based treatment at the point of care in Loa-endemic regions would allow resumption/expansion of mass drug administration programs for onchocerciasis and lymphatic filariasis in Central Africa.
authors.affiliation: Department of Bioengineering, University of California (UC), Berkeley, Berkeley, CA 94720, USA.
authors.forename: Michael V
authors.initials: MV
authors.lastname: D'Ambrosio
authors.affiliation: Department of Bioengineering, University of California (UC), Berkeley, Berkeley, CA 94720, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Bakalar
authors.affiliation: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA.
authors.forename: Sasisekhar
authors.initials: S
authors.lastname: Bennuru
authors.affiliation: Department of Bioengineering, University of California (UC), Berkeley, Berkeley, CA 94720, USA.
authors.forename: Clay
authors.initials: C
authors.lastname: Reber
authors.affiliation: Department of Bioengineering, University of California (UC), Berkeley, Berkeley, CA 94720, USA.
authors.forename: Arunan
authors.initials: A
authors.lastname: Skandarajah
authors.affiliation: Department of Bioengineering, University of California (UC), Berkeley, Berkeley, CA 94720, USA.
authors.forename: Lina
authors.initials: L
authors.lastname: Nilsson
authors.affiliation: Department of Bioengineering, University of California (UC), Berkeley, Berkeley, CA 94720, USA. Biophysics Graduate Group, UC Berkeley, Berkeley, CA 94720, USA.
authors.forename: Neil
authors.initials: N
authors.lastname: Switz
authors.affiliation: Center for Research on Filariasis and other Tropical Diseases, Yaoundé, Cameroon. Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon.
authors.forename: Joseph
authors.initials: J
authors.lastname: Kamgno
authors.affiliation: Center for Research on Filariasis and other Tropical Diseases, Yaoundé, Cameroon. UMI 233, Institut de Recherche pour le Développement and University of Montpellier, Montpellier, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Pion
authors.affiliation: UMI 233, Institut de Recherche pour le Développement and University of Montpellier, Montpellier, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Boussinesq
authors.affiliation: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA. fletch@berkeley.edu tnutman@niaid.nih.gov.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Nutman
authors.affiliation: Department of Bioengineering, University of California (UC), Berkeley, Berkeley, CA 94720, USA. Biophysics Graduate Group, UC Berkeley, Berkeley, CA 94720, USA. fletch@berkeley.edu tnutman@niaid.nih.gov.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Fletcher
mesh_terms: D000350:Africa, Central; D000465:Algorithms; D000818:Animals; D001331:Automation; D002163:Cameroon; D040421:Cell Phone; D004605:Elephantiasis, Filarial / Q000175:diagnosis*; D005188:False Negative Reactions; D007091:Image Processing, Computer-Assisted; D008117:Loa / Q000302:isolation & purification*; D018715:Microscopy, Video / Q000379:methods*; D009038:Motion; D009855:Onchocerciasis / Q000175:diagnosis*; D019095:Point-of-Care Systems; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity