title: Repurposed automated handheld counter as a point-of-care tool to identify individuals 'at risk' of serious post-ivermectin encephalopathy.
abstract: BACKGROUND
  Administration of ivermectin (IVM) as part of mass drug administration (MDA) campaigns for onchocerciasis and/or lymphatic filariasis (LF) has been suspended in areas co-endemic for Loa loa due to severe post-treatment adverse events (SAEs) associated with high-burden of infection (>30,000 mf/ml). One simple approach for preventing SAEs is to identify and exclude individuals at risk from MDA. Here, we describe a repurposed hand-held automated cell counter (Scepter 2.0; HHAC) as a rapid, point-of-care method for quantifying microfilariae (mf) in the blood of infected individuals.
  
  
  RESULTS
  The quantification of microfilarial levels in blood of naturally infected humans, experimentally infected baboons, or mf-spiked human blood was tested using a microfluidic-based automated counter and compared to traditional calibrated thick-smears. We demonstrate that mf can be quantified in 20 µl of whole blood following lysis with 10% saponin within a minute of obtaining blood. There was a highly significant concordance between the counts obtained by the HHAC and those by microscopy for mf densities of >5,000 (p<0.0001, r(c) = 0.97) or >30,000 per ml (p<0.0001, r(c) = 0.90). Preliminary proof of concept field studies in Cameroon with 20 µl of blood from L. loa infected humans (n = 22) and baboons (n = 4) also demonstrated a significantly high concordance (p<0.0001, r(c) = 0.89) with calibrated thick blood smears counts.
  
  
  CONCLUSIONS
  A repurposed HHAC is a portable, sensitive, rapid, point-of-care and quantitative tool to identify individuals with high levels of L. loa mf that put them at risk for SAEs following MDA. In addition, it provides ease of data storage and accessibility.
authors.affiliation: National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Sasisekhar
authors.initials: S
authors.lastname: Bennuru
authors.affiliation: UMI 233, Institut de Recherche pour le Développement (IRD) and University of Montpellier, Montpellier, France; Center for Research on Filariasis and other Tropical Diseases, Yaoundé, Cameroon.
authors.forename: Sébastien D S
authors.initials: SD
authors.lastname: Pion
authors.affiliation: Center for Research on Filariasis and other Tropical Diseases, Yaoundé, Cameroon; Faculty of Medicine and Biomedical Sciences, University of Yaoundé, Yaoundé, Cameroon.
authors.forename: Joseph
authors.initials: J
authors.lastname: Kamgno
authors.affiliation: Research Foundation in Tropical Diseases and the Environment, Buea, Cameroon; Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.
authors.forename: Samuel
authors.initials: S
authors.lastname: Wanji
authors.affiliation: National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Nutman
mesh_terms: D000818:Animals; D000977:Antiparasitic Agents / Q000009:adverse effects / Q000627:therapeutic use; D001927:Brain Diseases / Q000139:chemically induced*; D002163:Cameroon; D002452:Cell Count; D006801:Humans; D007559:Ivermectin / Q000009:adverse effects* / Q000627:therapeutic use*; D008117:Loa; D008118:Loiasis / Q000097:blood / Q000150:complications* / Q000188:drug therapy / Q000453:epidemiology; D008297:Male; D008315:Malondialdehyde; D008842:Microfilariae / Q000469:parasitology*; D010215:Papio; D019095:Point-of-Care Systems
chemical_list: D000977:Antiparasitic Agents; D008315:Malondialdehyde; D007559:Ivermectin