Analysis of menisci formed on cones for single field of view parasite egg microscopy

Abstract

Parasite ova caused to accumulate in a single microscopic field simplifies monitoring soil-transmitted helminthiasis by optical microscopy. Here we demonstrate new egg-accumulating geometries based on annular menisci formed on the surface of a wetted cone. Fluidic features extracted from profile images of the system provided mathematical representations of the meniscus gradient that were compared quantitatively to numerical solutions of an axisymmetric Young-Laplace equation. Our results show that the governing dynamics of these systems is dominated by the surface tension of the fluid. These image analysis and mathematical tools provide simple quantitative methods for system analysis and optimization.

Smartphone Microscopy of Parasite Eggs Accumulated into a Single Field of View

“… ) to passively accumulate buoyant nematode ova into a single FOV. 18 – 20 These menisci form about a tapered glass rod (3 mm diameter) located within a fluid well. The fluidic geometry is dominated by the surface tension at the liquid–air interface according to well-known physical laws of capillarity.…”

“…Manually finding and discriminating eggs from debris in stool by traditional microscopy is laborious and, combined with the rapid clearing of hookworm ova in the Kato–Katz method, limits quality-assured fecal egg counting and the monitoring of STH. 17 Here, we provide proof of concept for an alternative approach that uses fluidic geometries to concentrate eggs into a single FOV 18 – 20 and combines this with mobile phone digital photomicroscopy. 21 – 23 …”

Automated parasite faecal egg counting using fluorescence labelling, smartphone image capture and computational image analysis

“…Despite this burgeoning need and the development of sophisticated diagnostics in other areas of human and veterinary medicine, egg counting has remained relatively unchanged since the first method descriptions almost a century ago (Stoll, 1930;Gordon and Whitlock, 1939), although useful innovation has been introduced by enlarging flotation chamber volumes to improve sensitivity (Cringoli et al, 2004;Levecke et al, 2012;Barda et al, 2013), exploration of alternative flotation solutions (Cringoli et al, 2004;Vadlejch et al, 2011), and by developing flotation chamber adaptors to allow direct centrifugation-enhanced flotation (Cringoli et al, 2010). Recent work has illustrated the potential for utilizing novel imaging modalities and using computational image analysis to identify eggs and generate parasite FECs, and this technological field is rapidly evolving (Yang et al, 2001;Castanon et al, 2007;Mes et al, 2007;Dogantekin et al, 2008;Ghazali et al, 2013;Linder et al, 2013;Suzuki et al, 2013;Cooke et al, 2015).…”

Rationale for Quality Assurance in Fecal Egg Monitoring of Soil-Transmitted Helminthiasis

“…In the Kato-Katz method, a volumetric semisolid stool specimen is spread thinly over an area of approximately 490 mm 2 , which equates to approximately 31 and 197 nonoverlapping fields of view (FOV) at 40× and 100× magnification, respectively 10. For the McMaster and FLOTAC methods, the areas of fluidized stool to be imaged range from 100 to 324 mm 2 10. The lack of routine quality assurance in STH monitoring is complicated by the technical challenge of accurately counting helminth eggs 11.…”

“…The notion of digitizing and transmitting single FOV images could eliminate the need for trained parasitology microscopists from the field and aid in quality-assured monitoring of STHs by providing storable images for reexamination 10,19. Additional features could inform precise geographical distribution of STH infection via global positioning systems and provide rapid transmission of relevant data to cloud-based services for widespread dissemination and geospatial mapping 5.…”