Conventional parasitology and DNA-based diagnostic methods for onchocerciasis elimination programmes

• Published in: Acta tropica 2015-06, Vol.146, p.114-118
• Main Authors: Lloyd, Melanie M., Gilbert, Rebecca, Taha, Nathalie Tebao, Weil, Gary J., Meite, Aboulaye, Kouakou, Ilunga M.M., Fischer, Peter U.
• Format: Article
• Language: English
• Subjects: Adult; Animals; Cote d'Ivoire; Diagnosis; Female; Humans; Ivermectin - therapeutic use; Male; Microfilariae - drug effects; Middle Aged; Molecular diagnostics; Onchocerca - drug effects; Onchocerciasis; Onchocerciasis - diagnosis; Onchocerciasis - prevention & control; Prevalence; qPCR; Real-Time Polymerase Chain Reaction; Skin - parasitology
• ISSN: 0001-706X; 1873-6254
• DOI: 10.1016/j.actatropica.2015.03.019

In this study, a qPCR assay was designed to test for Onchocerca volvulus DNA in dried skin snips after MF emerged. Results of this assay were compared to traditional diagnostic methods: microscopic detection of MF in skin snips and nodule palpation. The combination of molecular methods and traditional parasitological methods increases the prevalence estimation significantly. •A qPCR assay was designed to test for onchocerca DNA in dried skin snips.•Assay results were compared to traditional methods: MF and nodule identification.•Combining molecular and traditional methods increases prevalence estimation. Commonly used methods for diagnosing Onchocerca volvulus infections (microscopic detection of microfilariae in skin snips and nodule palpation) are insensitive. Improved methods are needed for monitoring and evaluation of onchocerciasis elimination programmes and for clinical diagnosis of individual patients. A sensitive probe-based qPCR assay was developed for detecting O. volvulus DNA, and this was tested with samples collected from an endemic area in eastern Côte d’Ivoire. The new test was evaluated with dried skin snip pairs from 369 subjects and compared to routine skin snip microscopy and nodule palpation results from the same individuals. Onchocerciasis prevalence for these samples by qPCR, skin snip microscopy, and nodule palpation were 56.9%, 26.0%, and 37.9%, respectively. Furthermore, the combination of all three tests produced an infection prevalence of 72.9%, which was significantly higher than 53.1% detected by microscopy plus nodule palpation without qPCR. However, the qPCR assay was negative for 54 of 229 individuals with palpable nodules. qPCR could be a useful tool for detecting residual O. volvulus infections in human populations as prevalence decreases in areas following community-directed treatment with ivermectin.