Unusual localization of blood-borne loa loa microfilariae in the skin depends on microfilarial density in the blood: Implications for onchocerciasis diagnosis in coendemic areas.
File(s)
Supporting information
Author(s)
Niamsi-Emalio, Yannick
Nana-Djeunga, Hugues C
Chesnais, Cédric B
Pion, Sébastien DS
Tchatchueng-Mbougua, Jules B
Type
Journal Article
Abstract
BACKGROUND: The diagnostic gold standard for onchocerciasis relies on identification and enumeration of (skin-dwelling) Onchocerca volvulus microfilariae (mf) using the skin snip technique (SST). In a recent study, blood-borne Loa loa mf were found by SST in individuals heavily infected with L. loa, and microscopically misidentified as O. volvulus due to their superficially similar morphology. This study investigates the relationship between L. loa microfilarial density (Loa MFD) and the probability of testing SST positive. METHODS: A total of 1053 participants from the (onchocerciasis and loiasis coendemic) East Region in Cameroon were tested for (1) Loa MFD in blood samples, (2) O. volvulus presence by SST, and (3) Immunoglobulin (Ig) G4 antibody positivity to Ov16 by rapid diagnostic test (RDT). A Classification and Regression Tree (CART) model was used to perform a supervised classification of SST status and identify a Loa MFD threshold above which it is highly likely to find L. loa mf in skin snips. RESULTS: Of 1011 Ov16-negative individuals, 28 (2.8%) tested SST positive and 150 (14.8%) were L. loa positive. The range of Loa MFD was 0-85 200 mf/mL. The CART model subdivided the sample into 2 Loa MFD classes with a discrimination threshold of 4080 (95% CI, 2180-12 240) mf/mL. The probability of being SST positive exceeded 27% when Loa MFD was >4080 mf/mL. CONCLUSIONS: The probability of finding L. loa mf by SST increases significantly with Loa MFD. Skin-snip polymerase chain reaction would be useful when monitoring onchocerciasis prevalence by SST in onchocerciasis-loiasis coendemic areas.
Date Issued
2021-06-14
Date Acceptance
2021-06-01
Citation
Clinical Infectious Diseases, 2021, 72 (Supplement_3), pp.S158-S164
ISSN
1058-4838
Publisher
Oxford University Press
Start Page
S158
End Page
S164
Journal / Book Title
Clinical Infectious Diseases
Volume
72
Issue
Supplement_3
Copyright Statement
© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/33909066
PII: 6256993
Subjects
Loa loa
Onchocerca volvulus
classification and regression tree model
diagnosis
skin snip technique
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2021-06-14