Quantifying ascaris : changing the game in the fight against parasitic worms
Abstract/Contents
- Abstract
- The intestinal worm Ascaris infects approximately 15% of the global population, impairing cognitive development and stunting growth in children and preventing beneficial use of biosolids as a soil amendment. Current assays have high variance and are time-consuming. More rapid, accurate methods will improve clinical diagnostics and ensure the effectiveness of technologies that inactivate Ascaris eggs in biosolids prior to their use in agriculture. A systematic literature review of quantification methods revealed significant heterogeneity between studies, all of which involve the following steps: (1) separation of eggs from a sample matrix (soil, feces, biosolids, water), (2) sedimentation or flotation to concentrate eggs, and (3) counting of eggs by microscopy, including egg viability assessments for inactivation studies. A meta-regression found that assay variables with greatest positive impact on recovery rates achieved in steps (1) and (2) are use of higher density flotation solutions and 7X surfactant. For Step (3), observer-based microscopy poses an obstacle to quantification in a timely and accurate manner. Assessment of inactivation is the most time-consuming step, typically requiring egg incubation for 15-35 days. The review also addresses the widespread adoption of a "Gold Standard" based upon a consensus of methods that vary from study-to-study. This lack of standardization leads to under-reporting of prevalence and difficulties in comparing methods. An improved gold standard is recommended that incorporates standardized use of the method of known addition (i.e., split/spike) to account for differences in egg recovery efficiencies from different environmental matrices. To overcome limitations of current methods, we investigated properties of Ascaris eggs that could lead to faster and more reliable egg concentration, we developed an algorithm for automated counting of Ascaris eggs in wide field microscopy (Chapter 2), and we developed an assay for determining viable eggs based on amplification of mRNA within eggs (Chapter 3).
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2018; ©2018 |
| Publication date | 2018; 2018 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Strong, Nathaniel I |
|---|---|
| Degree supervisor | Criddle, Craig |
| Thesis advisor | Criddle, Craig |
| Thesis advisor | Luby, Stephen |
| Thesis advisor | Spormann, Alfred M |
| Thesis advisor | Tang, Sindy (Sindy K.Y.) |
| Degree committee member | Luby, Stephen |
| Degree committee member | Spormann, Alfred M |
| Degree committee member | Tang, Sindy (Sindy K.Y.) |
| Associated with | Stanford University, Civil & Environmental Engineering Department. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Nathaniel I. Strong. |
|---|---|
| Note | Submitted to the Civil and Environmental Engineering Department. |
| Thesis | Thesis Ph.D. Stanford University 2018. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2018 by Nathaniel I Strong
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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