Evaluation of a larval development assay (DrenchRite) for the detection of anthelmintic resistance in cyathostomin nematodes of horses.
Abstract: A larval development assay (LDA, DrenchRite) was evaluated to determine the effectiveness of this method in detecting anthelmintic resistance in cyathostomin nematodes of horses. A total of 15 horse farms from Georgia and South Carolina (USA) and Population S ponies from the University of Kentucky (USA) were included in this study. Nematode eggs were extracted from pooled fecal samples and placed into the wells of a DrenchRite plate for testing against thiabendazole (TBZ), levamisole (LEV) and 2 ivermectin (IVM) analogs (IVM-1, IVM-2). After a 7-day incubation larvae in each well were counted and data were analyzed by logistic regression. Resistance status of each farm for different drugs was determined in a separate study using a fecal egg count reduction test. LDA were performed on the 15 farms once, however, the Population S cyathostomins were assayed on 3 separate occasions to estimate the consistency of results between assays. Mean TBZ LC50 for oxibendazole resistant, suspected resistant and sensitive farms were 0.2015, 0.1625, and 0.1355 microM, respectively. For LEV, mean LC50 for PYR resistant, suspected resistant and sensitive farms were 1.590, 1.8018 and 1.4219 microM, respectively. All 15 farms had worms susceptible to IVM; mean LC50 for IVM-1 and for IVM-2 were 7.5727 and 87.9718 nM, respectively. A linear mixed model was fitted to the data to determine the relationship between LC50 and LC95 and resistance status for each farm. No meaningful relations were found. Consistency of assays varied between drugs, being best for TBZ and worst for LEV and IVM-1. All farms in this study had benzimidazole-resistant nematodes; therefore usefulness of DrenchRite for discriminating susceptibility versus resistance to this drug class could not be accurately assessed. Moreover, since all farms tested were sensitive to IVM and resistance to this drug class has not yet been reported in cyathostomins, it is not possible to assess accurately the usefulness of DrenchRite LDA for detecting IVM resistance at this time. Assay results for LEV suggest that LEV in a LDA does not yield data that is useful in estimating PYR efficacy in vivo. Based on results for PYR/LEV, the current high prevalence of benzimidazole resistance, no known cases of IVM resistance, and the sometimes extreme variation in results seen in many of the assays, DrenchRite LDA cannot be considered a useful tool for the diagnosis of resistance in cyathostomins of horses at present.
Copyright 2004 Elsevier B.V.
Publication Date: 2004-04-28 PubMed ID: 15110410DOI: 10.1016/j.vetpar.2003.09.016Google Scholar: Lookup
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- Evaluation Study
- Journal Article
Summary
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This study evaluated the effectiveness of a larval development assay (DrenchRite LDA) in identifying resistance to deworming drugs in horse nematodes. Researchers found that despite testing on a range of different farms, DrenchRite was unable to consistently produce meaningful data to evaluate resistance. Consequently, the researchers concluded that DrenchRite is currently not a useful tool for diagnosing resistance in these parasites.
Methodology
- The research was conducted on 15 horse farms in Georgia and South Carolina, as well as with a population of ponies from the University of Kentucky.
- Nematode eggs were extracted from combined fecal samples and tested using the DrenchRite LDA against various anthelmintic drugs such as thiabendazole (TBZ), levamisole (LEV), and two ivermectin (IVM) analogs.
- The larvae were incubated for 7 days, after which the larvae in each well were counted, and the data were analyzed using a logistic regression.
- A different study determined the resistance status of each farm to the different drugs.
- The DrenchRite LDA was performed just once on the 15 farms, but the Population S cyathostomins were tested three times to evaluate the consistency of the results between assays.
Findings
- All farms in the research showed resistance to benzimidazole, but sensitivity to IVM; hence, the usefulness of DrenchRite LDA in differentiating between susceptibility and resistance was not accurately assessed.
- The consistency of the assays greatly varied between drugs with the best results produced for TBZ and the worst for LEV and IVM-1.
- The study found no meaningful relationship between LC50 and LC95 (the concentration that is lethal to 50% and 95% of the population, respectively) and the resistance status for each farm, after fitting a linear mixed model to the data.
Conclusions
- Due to the prevalence of benzimidazole resistance, the absence of known IVM resistance, and the varying results in many of the assays, DrenchRite LDA was deemed not useful for diagnosing resistance in nematodes of horses currently.
- The assay results for LEV indicated that it does not yield data that is helpful in estimating LEV effectiveness in vivo.
- The study concluded that more accurate methods are needed to detect drug resistance in horse nematodes.
Cite This Article
APA
Tandon R, Kaplan RM.
(2004).
Evaluation of a larval development assay (DrenchRite) for the detection of anthelmintic resistance in cyathostomin nematodes of horses.
Vet Parasitol, 121(1-2), 125-142.
https://doi.org/10.1016/j.vetpar.2003.09.016 Publication
Researcher Affiliations
- Department of Medical Microbiology and Parasitology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
MeSH Terms
- Animals
- Antinematodal Agents / pharmacology
- Drug Resistance
- Feces / parasitology
- Horse Diseases / parasitology
- Horses
- Ivermectin / pharmacology
- Larva / drug effects
- Larva / growth & development
- Levamisole / pharmacology
- Linear Models
- Nematoda / drug effects
- Nematoda / growth & development
- Nematode Infections / drug therapy
- Nematode Infections / parasitology
- Nematode Infections / veterinary
- Parasite Egg Count / veterinary
- Reagent Kits, Diagnostic / parasitology
- Reagent Kits, Diagnostic / veterinary
- Regression Analysis
- Reproducibility of Results
- Thiabendazole / pharmacology
Citations
This article has been cited 8 times.- Zhang X, Sicalo Gianechini L, Li K, Kaplan RM, Witola WH. Broad-Spectrum Inhibitors for Conserved Unique Phosphoethanolamine Methyltransferases in Parasitic Nematodes Possess Anthelmintic Efficacy.. Antimicrob Agents Chemother 2023 Jun 15;67(6):e0000823.
- Nezami R, Blanchard J, Godoy P. Compte rendu The canine hookworm Ancylostoma caninum: A novel threat for anthelmintic resistance in Canada.. Can Vet J 2023 Apr;64(4):372-378.
- Jesudoss Chelladurai JRJ, Martin KA, Chinchilla-Vargas K, Jimenez Castro PD, Kaplan RM, Brewer MT. Laboratory assays reveal diverse phenotypes among microfilariae of Dirofilaria immitis isolates with known macrocyclic lactone susceptibility status.. PLoS One 2020;15(8):e0237150.
- Jimenez Castro PD, Howell SB, Schaefer JJ, Avramenko RW, Gilleard JS, Kaplan RM. Multiple drug resistance in the canine hookworm Ancylostoma caninum: an emerging threat?. Parasit Vectors 2019 Dec 9;12(1):576.
- Peachey LE, Pinchbeck GL, Matthews JB, Burden FA, Lespine A, von Samson-Himmelstjerna G, Krücken J, Hodgkinson JE. P-glycoproteins play a role in ivermectin resistance in cyathostomins.. Int J Parasitol Drugs Drug Resist 2017 Dec;7(3):388-398.
- Arafa WM, Holman PJ, Craig TM. Genotypic and phenotypic evaluation for benzimidazole resistance or susceptibility in Haemonchus contortus isolates.. Parasitol Res 2017 Feb;116(2):797-807.
- Lake SL, Matthews JB, Kaplan RM, Hodgkinson JE. Determination of genomic DNA sequences for beta-tubulin isotype 1 from multiple species of cyathostomin and detection of resistance alleles in third-stage larvae from horses with naturally acquired infections.. Parasit Vectors 2009 Sep 25;2 Suppl 2(Suppl 2):S6.
- Lind EO, Kuzmina T, Uggla A, Waller PJ, Höglund J. A field study on the effect of some anthelmintics on cyathostomins of horses in sweden.. Vet Res Commun 2007 Jan;31(1):53-65.
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