Verweij, J. | bioRxiv Science

bioRxiv2026

Development, field-testing and optimization of tools to quantify soil-transmitted helminths in fecal sludge from school pit latrines in Ethiopia

BackgroundSurveys to monitor large-scale deworming programs against soil-transmitted helminthiases (STH) involve examination of stool samples from schoolchildren. These surveys are resource demanding and impact school activities. A potentially cost-saving alternative that does not involve children is to process fecal sludge samples from school pit latrines. To provide a proof-of-principle of latrine-based monitoring of STH programs, we optimized tools to collect fecal sludge and to quantify STH eggs in the samples. MethodsFirst, we designed, developed and field-tested three locally made fecal sludge sampling prototypes. Second, we developed a modified egg-counting method and conducted spiking experiments to explore its analytical performance. Third, we estimated the variation in egg counts in fecal sludge samples collected from six primary schools in Ethiopia at different pit latrine depths used by boys and girls and by repeatedly examining samples. Finally, field data were used to inform an egg count simulation model to quantify this variation in egg counts and to determine the sampling and analysis strategies that resulted in surveys as precise as a stool-based survey. ResultsThe modified fecal sludge sampling prototypes were generally successful, except for a few pit latrines with dried/solid sludge types and insufficient sludge volume. The egg-counting method had moderately high analytical sensitivity that varied across the consistency of the samples. The variation in egg counts was mainly explained by differences between squat holes followed by repeated fecal sludge sample processing. Latrine-based surveys were as precise as stool-based surveys only for Ascaris and when the intensity of infections was low. ConclusionsWe developed a sampling and diagnostic strategy that we will use in a follow-up study. This study will be conducted in Jimma Zone across 25 schools (52 children per school) and will compare the mean fecal sludge egg counts at school level with the STH prevalence in children. Author summaryProgress of large-scale deworming programs are currently monitored through screening individual stool samples of schoolchildren. A latrine-based program monitoring, without active participation of schoolchildren and interruption of routine school activities, is a potentially cost-effective alternative. As a proof-of-concept, we developed a method to quantify worm eggs in fecal sludge samples, conducted spiking experiments to determine its analytical performance and applied the method across schools in Ethiopia to explore variation in egg counts (e.g., squat holes, depth of sample collection, and repeated analyses). Based on our findings, we then determined the sample collection and analysis strategy that results a latrine-based survey as precise as a survey based on screening individual stool samples. The analytical performance was moderately high but varied across the consistency of the samples. The variation in egg counts was mainly driven by variation between squat holes on the same pit latrine, and thus it is better to sample more squat holes (at least 3) than repeatedly processing the same fecal sludge sample (one examination is sufficient). We will now apply this sample collection and analysis across 25 schools (52 children per school) in Ethiopia and compare it with a survey based on screening individual stool samples.

microbiology↗

bioRxiv2019

Light responses of melanopsin-expressing ganglion cells in the foetal mammalian retina

Sensory stimulation plays a critical role in the maturation of sensory organs and systems. For example, when deprived of light before birth, foetal mouse pups in utero exhibit altered ocular vascular development. Normal vascular development depends on light excitation of melanopsin, a non-rod, non-cone photopigment that is expressed in a subset of ganglion cells (mRGCs) in the retina. However, there is no direct evidence that mRGCs in foetal eyes are light-responsive. Very little is known about how light absorption leads to excitation in these foetal neurons. Using mRGC-specific expression of the calcium indicators GCaMP3 and GCaMP6, we report that foetal mouse mRGCs respond to light as early as 4 days before birth. Further, two distinct Gq/11-G protein family antagonists, FR9000359 and YM-254890, abolish these light responses. TTX, a blocker of voltage-activated sodium channels, reversibly represses light responses, and FPL6417 and L-cis-diltiazem, which modify L-type calcium channels, respectively increase and reduce light responses. Electrophysiological patch pipette recordings show that embryonic mRGCs respond to light of intensity as low as 2.9 x 1012 photons/cm2/s. The present findings demonstrate a heretofore unproven but postulated light sensitivity in the retinas of foetal mice and identify the transduction pathways involved. Surprisingly, mRGCs do not function as completely independent photoreceptors but are electrotonically coupled with other mRGCs. Given that melanopsin is expressed in foetal human retinas, these findings support the idea that the eyes of foetal and early preterm infants are likely to exhibit functional photosensitivity.\n\nKey pointsO_LIMelanopsin is a light-excitable photopigment expressed in a subset of ganglion cell neurons (mRGCs) in the retinas of many different species of vertebrates. In mature animals, light activation of mRGCs modulates many visual adaptive functions including pupil constriction, entrainment of circadian rhythms, mood and learning. In neonatal pups at ages prior to the developmental onset of visual signalling from rods and cones, melanopsin cells mediate photoaversive behaviour. In foetal pups, light activation of melanopsin cells accelerates maturation of the ocular vasculature. Here, we describe and physiologically characterize the light responses of melanopsin ganglion cells in the retinas of foetal pups.\nC_LIO_LIMRGCs in embryonic retinas respond to light at least four days prior to birth and exhibit responses to light of intensity as low as 3 x 1012 photons/cm2/s.\nC_LIO_LIPhototransduction mechanisms include melanopsin activation of Gq/11 - G proteins, voltage-activated sodium currents, and voltage-gated L-type calcium currents.\nC_LIO_LIMRGCs are electrotonically coupled to other mRGCs in foetal retinas.\nC_LIO_LIWe propose that melanopsin-expressing ganglion cells are excited by light while in utero and that this excitation relies, for the most part, on phototransduction pathways that have been described in postnatal retinas. Furthermore, we propose that foetal mRGCs have the requisite properties to modulate light-regulated maturation of the ocular vasculature and, perhaps, the development of visual pathways.\nC_LI

neuroscience↗