title: Detection of Onchocerca volvulus in Skin Snips by Microscopy and Real-Time Polymerase Chain Reaction: Implications for Monitoring and Evaluation Activities.
abstract: Microscopic evaluation of skin biopsies is the monitoring and evaluation (M and E) method currently used by multiple onchocerciasis elimination programs in Africa. However, as repeated mass drug administration suppresses microfilarial loads, the sensitivity and programmatic utility of skin snip microscopy is expected to decrease. Using a pan-filarial real-time polymerase chain reaction with melt curve analysis (qPCR-MCA), we evaluated 1) the use of a single-step molecular assay for detecting and identifying Onchocerca volvulus microfilariae in residual skin snips and 2) the sensitivity of skin snip microscopy relative to qPCR-MCA. Skin snips were collected and examined with routine microscopy in hyperendemic regions of Uganda and Ethiopia (N= 500 each) and "residual" skin snips (tissue remaining after induced microfilarial emergence) were tested with qPCR-MCA. qPCR-MCA detected Onchocerca DNA in 223 residual snips: 139 of 147 microscopy(+) and 84 among microscopy(-) snips, suggesting overall sensitivity of microscopy was 62.3% (139/223) relative to qPCR-MCA (75.6% in Uganda and 28.6% in Ethiopia). These findings demonstrate the insufficient sensitivity of skin snip microscopy for reliable programmatic monitoring. Molecular tools such as qPCR-MCA can augment sensitivity and provide diagnostic confirmation of skin biopsies and will be useful for evaluation or validation of new onchocerciasis M and E tools.
authors.affiliation: Parasitic Diseases Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Vector Control Division, Ministry of Health, Kampala, Uganda; Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Thiele
authors.affiliation: Parasitic Diseases Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Vector Control Division, Ministry of Health, Kampala, Uganda; Ethiopian Public Health Institute, Addis Ababa, Ethiopia vcama@cdc.gov.
authors.forename: Vitaliano A
authors.initials: VA
authors.lastname: Cama
authors.affiliation: Parasitic Diseases Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Vector Control Division, Ministry of Health, Kampala, Uganda; Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
authors.forename: Thomson
authors.initials: T
authors.lastname: Lakwo
authors.affiliation: Parasitic Diseases Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Vector Control Division, Ministry of Health, Kampala, Uganda; Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
authors.forename: Sindeaw
authors.initials: S
authors.lastname: Mekasha
authors.affiliation: Parasitic Diseases Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Vector Control Division, Ministry of Health, Kampala, Uganda; Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
authors.forename: Francisca
authors.initials: F
authors.lastname: Abanyie
authors.affiliation: Parasitic Diseases Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Vector Control Division, Ministry of Health, Kampala, Uganda; Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
authors.forename: Markos
authors.initials: M
authors.lastname: Sleshi
authors.affiliation: Parasitic Diseases Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Vector Control Division, Ministry of Health, Kampala, Uganda; Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
authors.forename: Amha
authors.initials: A
authors.lastname: Kebede
authors.affiliation: Parasitic Diseases Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Vector Control Division, Ministry of Health, Kampala, Uganda; Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Cantey
mesh_terms: D000818:Animals; D001706:Biopsy; D002648:Child; D005002:Ethiopia; D006801:Humans; D008853:Microscopy / Q000379:methods; D017181:Onchocerca volvulus; D009855:Onchocerciasis / Q000175:diagnosis* / Q000473:pathology; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D012867:Skin / Q000469:parasitology; D014454:Uganda