Reliability of Detection of Microfilariae in Skin Snips in the Diagnosis of Onchocerciasis

Taylor, Hugh R.; Muñoz, Beatriz; Keyvan-Larijani, Ezatollah; Greene, Bruce M.

doi:10.4269/ajtmh.1989.41.467

Cited by 63 publications

(65 citation statements)

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“…The difference was most likely due to the different ways in which the skin biopsies were examined. The traditional method (as used by Raccurt et al 1982) involves incubating the skin biopsy in a suitable fluid and then counting the number of microfilariae which emerge, but it has been established for O. volvulus that many microfilariae remain inside the biopsy and are therefore undetected (Schulz-Key, 1978 ;Taylor et al 1989). The molecular method on the other hand involves the extraction of DNA from the whole (unincubated) skin biopsy and the subsequent detection of parasite DNA.…”

Section: Introductionmentioning

confidence: 99%

The morphological discrimination of microfilariae of Onchocerca volvulus from Mansonella ozzardi

et al. 2003

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There is no published account which allows the morphological discrimination of microfilariae of Onchocerca volvulus and M. ozzardi from each other. However, they occur together in parts of Brazil and Venezuela, and presumably there is always the possibility that migration could establish new sympatric populations in the future. The objective of this study was to evaluate simple morphological characters that might be used for species-diagnosis of microfilariae. The conclusions were that the location of microfilariae in the blood or skin, the body size and the nucleation of the nerve ring are expected to be useful first indications of species identity, but cannot be used for confident diagnosis. The structure of the cephalic armature (stained with alcian blue) seems to be species specific, but is of limited application because it is often difficult to see. However, the pattern of nucleation of the tail (as expressed by the ratio of the length of the terminal nucleus compared with the length of the tail space) is distinctive and is expected to be diagnostic.

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Section: Introductionmentioning

confidence: 99%

The morphological discrimination of microfilariae of Onchocerca volvulus from Mansonella ozzardi

et al. 2003

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“…However, reduced microfiladermia is accompanied by reduced sensitivity of skin snip microscopy. 8 Thus, IVM MDA and the associated sustained suppression of microfiladermia are expected to further reduce the sensitivity of skin snip microscopy in later stages of program M and E. 7,9 Moreover, sensitivity of skin snip microscopy is also known to be limited in hypoendemic areas, further calling into question its utility for mapping as elimination programs expand to include regions of reduced endemicity. 10 Here we describe the design and evaluation of a singlestep DNA-based method to detect patent O. volvulus infection in skin snips as an alternative to microscopic evaluation.…”

Section: Introductionmentioning

confidence: 99%

Detection of Onchocerca volvulus in Skin Snips by Microscopy and Real-Time Polymerase Chain Reaction: Implications for Monitoring and Evaluation Activities

Thiele¹,

Cama²,

Lakwo³

et al. 2016

The American Society of Tropical Medicine and Hygiene

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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.

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“…Definitive proof of active infection due to O. volvulus is by microscopic demonstration of worms in skin snips or in nodules surgically excised from suspects. Unfortunately, the commonly used skin snip method is insensitive in low transmission areas and in areas where long-term use of the microfilaricidal ivermectin has resulted in significant reduction of both individual and community skin microfilariae loads (Taylor et al (1989); Newell (1997)), with a consequential reduction in the prevalence of most signs and symptoms of the disease. Furthermore, the skin snip procedure is painful and involves a high risk of bloodborne infections (e.g.…”

Section: Introductionmentioning

confidence: 99%

Development and evaluation of an antigen detection dipstick assay for the diagnosis of human onchocerciasis

Ayong

Tume

Wembe

et al. 2005

Trop Med Int Health

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SummaryTo improve on the diagnosis of onchocerciasis, especially light infections, we developed and evaluated an oncho-dipstick test based on the detection of Onchocerca volvulus specific antigens in urine and tears. The test was able to detect as little as 25 ng/ml of parasite specific antigens in samples and took as little as 3 h. Evaluation of the assay on 456 residents of an onchocerciasis hyperendermic area in Cameroon resulted in 408 (89.5%) positives in urine and 374 (82%) positives in tears. The prevalence of onchocerciasis in the study area, as determined by Rapid Epidemiological Mapping of Onchocerciasis (REMO) and skin snip methods, was 52 and 36.8%, respectively. The sensitivity of the oncho-dipstick assay was 100% in urine and 92% in tears; its specificity was 100% in both. Concordance between urine and tear test results from the same individuals was 87%. The test strips were sufficiently reactive when left at room temperature for up to 8 months. The test would be useful for laboratory diagnosis of onchocerciasis in low transmission zones and to ascertain successful treatment of patients in experimental drug studies.

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Reliability of Detection of Microfilariae in Skin Snips in the Diagnosis of Onchocerciasis

Cited by 63 publications

References 0 publications

The morphological discrimination of microfilariae of Onchocerca volvulus from Mansonella ozzardi

The morphological discrimination of microfilariae of Onchocerca volvulus from Mansonella ozzardi

Detection of Onchocerca volvulus in Skin Snips by Microscopy and Real-Time Polymerase Chain Reaction: Implications for Monitoring and Evaluation Activities

Development and evaluation of an antigen detection dipstick assay for the diagnosis of human onchocerciasis

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