The potential impact of density dependent fecundity on the use of the faecal egg count reduction test for detecting drug resistance in human hookworms

Kotze, Andrew C. and Kopp, Steven (2008) The potential impact of density dependent fecundity on the use of the faecal egg count reduction test for detecting drug resistance in human hookworms. PLoS Neglected Tropical Diseases, 2 10: e297 -1-e297 -6. doi:10.1371/journal.pntd.0000297


Author Kotze, Andrew C.
Kopp, Steven
Title The potential impact of density dependent fecundity on the use of the faecal egg count reduction test for detecting drug resistance in human hookworms
Journal name PLoS Neglected Tropical Diseases   Check publisher's open access policy
ISSN 1935-2735
Publication date 2008-10
Sub-type Article (original research)
DOI 10.1371/journal.pntd.0000297
Open Access Status DOI
Volume 2
Issue 10
Start page e297 -1
End page e297 -6
Total pages 6
Editor Jeffrey Bethony
Place of publication San Francisco, United States
Publisher Public Library of Science
Collection year 2009
Language eng
Subject C1
110803 Medical Parasitology
970111 Expanding Knowledge in the Medical and Health Sciences
Abstract Current efforts to control human soil-transmitted helminth (STH) infections involve the periodic mass treatment of people, particularly children, in all endemic areas, using benzimidazole and imidothiazole drugs. Given the fact that high levels of resistance have developed to these same drugs in roundworms of livestock, there is a need to monitor drug efficacy in human STHs. The faecal egg count reduction test (FECRT), in which faecal egg output is measured pre- and post-drug treatment, is presently under examination by WHO as a means of detecting the emergence of resistance. We have examined the potential impact of density dependent fecundity on FECRT data. Recent evidence with the canine hookworm indicates that the density dependent egg production phenomenon shows dynamic properties in response to drug treatment. This will impact on measurements of drug efficacy, and hence drug resistance. It is likely that the female worms that survive a FECRT drug treatment in some human cases will respond to the relaxation of density dependent constraints on egg production by increasing their egg output significantly compared to their pre-treatment levels. These cases will therefore underestimate drug efficacy in the FECRT. The degree of underestimation will depend on the ability of the worms within particular hosts to increase their egg output, which will in turn depend on the extent to which their egg output is constrained prior to the drug treatment. As worms within different human cases will likely be present at quite different densities prior to a proposed FECRT, there is potential for the effects of this phenomenon on drug efficacy measurements to vary considerably within any group of potential FECRT candidates. Measurement of relative drug efficacy may be improved by attempting to ensure a consistent degree of underestimation in groups of people involved in separate FECRTs. This may be partly achieved by omission of cases with the heaviest infections from a FECRT, as these cases may have the greatest potential to increase their egg output upon removal of density dependent constraints. The potential impact of worm reproductive biology on the utility of the FECRT as a resistance detection tool highlights the need to develop new drug resistance monitoring methods which examine either direct drug effects on isolated worms with in vitro phenotypic assays, or changes in worm genotypes.
Keyword Trichuris-trichiura infection
Nematode strongyloides-ratti
Ascaris-lumbricoides
Population biology
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Article number e297

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2009 Higher Education Research Data Collection
School of Veterinary Science Publications
 
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Citation counts: TR Web of Science Citation Count  Cited 20 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 23 times in Scopus Article | Citations
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Created: Thu, 02 Apr 2009, 15:24:53 EST by Narelle Poole on behalf of School of Veterinary Science