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Home / Equine Research Bank / Int J Parasitol Drugs Drug Resist / Quantitative DNA metabarcoding reveals species composition o...
International journal for parasitology. Drugs and drug resistance2024; 27; 100576; doi: 10.1016/j.ijpddr.2024.100576

Quantitative DNA metabarcoding reveals species composition of a macrocyclic lactone and pyrantel resistant cyathostomin population in the UK.

Abstract: Cyathostomins are the most abundant equid endoparasites globally. There are approximately fifty cyathostomin species and, whilst they occupy distinct niches within the large intestine, they are generally considered to share similar characteristics in terms of pathogenicity and response to drug treatment. There are three classes of anthelmintic licensed in the UK to treat cyathostomins (benzimidazoles, tetrahydropyrimidines and macrocyclic lactones) and cases of resistance have been documented for all classes. Previously, faecal egg count reduction tests (FECRT) on four UK Thoroughbred studs revealed multidrug resistant cyathostomins on one stud (A), with evidence of resistance to the macrocyclic lactones (MLs) ivermectin (IVM) and moxidectin (MOX), and to pyrantel (PYR). The remaining three studs (B-D) lacked resistance to IVM and MOX but had a shortened egg reappearance period post treatment. To determine whether specific species could be associated with the observed resistance and shortened egg reappearance period, strongyle eggs collected from between six and 15 individual horses per stud were copro-cultured to third larval stage (L3), before and after anthelmintic treatment, over a three-year timeframe (2021-2023). Quantitative DNA metabarcoding of the ITS-2 region was carried out on all samples. On stud A, single but differing species were found to be responsible for ML and pyrantel resistance in yearlings, Cyathostomum catinatum and Cylicocyclus nassatus, respectively. On studs B-D, with shortened egg reappearance periods, species composition remained largely unchanged post treatment. This study is the first to quantitatively profile cyathostomin species composition pre- and post-treatment in a multidrug resistant population in the UK, revealing that resistance in cyathostomins was species specific. This raises the question of whether these species may be responsible for ML and PYR resistance more widely and indicates that anthelmintic resistance in cyathostomins may not be a multi-species phenomenon.
Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.
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Publication Date: 2024-12-22 PubMed ID: 39778419PubMed Central: PMC11762968DOI: 10.1016/j.ijpddr.2024.100576Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This research investigates the species composition of cyathostomin parasites in UK horses that show resistance to common anthelmintic drugs, specifically macrocyclic lactones and pyrantel.
  • Using DNA metabarcoding, the study identifies which specific parasite species are linked to drug resistance, revealing species-specific resistance rather than a generalized multi-species phenomenon.

Background

  • Cyathostomins are the most common internal parasites of horses worldwide, with around 50 known species.
  • Although these species occupy slightly different niches in the horse’s large intestine, they are generally assumed to have similar impacts on health and response to treatments.
  • In the UK, three classes of anthelmintics (anti-parasitic drugs)—benzimidazoles, tetrahydropyrimidines, and macrocyclic lactones—are licensed to treat cyathostomin infections.
  • Cases of parasite resistance (i.e., the parasites surviving treatment) to all these drug classes have been documented.

Previous Observations

  • Faecal egg count reduction tests (FECRT) on four UK Thoroughbred studs indicated multi-drug resistance in one stud (A), including resistance to macrocyclic lactones (ivermectin and moxidectin) and to pyrantel.
  • The other three studs (B-D) did not show resistance to macrocyclic lactones but exhibited a shortened egg reappearance period after treatment, indicating faster return of parasite eggs in feces.

Research Aim and Approach

  • The researchers aimed to determine whether specific cyathostomin species were associated with the observed drug resistance and shortened egg reappearance.
  • They collected strongyle eggs from 6 to 15 individual horses per stud over a three-year period (2021-2023).
  • Eggs were cultured to the third larval stage (L3) both before and after treatment with anthelmintics.
  • Quantitative DNA metabarcoding targeting the ITS-2 region of parasite DNA was conducted on all samples to identify and quantify species composition.

Key Findings

  • On stud A, which had multidrug resistance, two different species were implicated in drug resistance:
    • Cyathostomum catinatum was linked to macrocyclic lactone resistance.
    • Cylicocyclus nassatus was linked to pyrantel resistance.
  • The other studs (B-D), which had a shortened egg reappearance period but no full resistance, showed little change in species composition after treatment.
  • This indicates that drug resistance in cyathostomins can be specific to particular species rather than affecting multiple species equally.

Significance and Implications

  • This study is the first to quantitatively observe species-level changes in cyathostomin populations in response to anthelmintic treatment in a multidrug resistant setting in the UK.
  • Identifying species-specific resistance patterns suggests that some cyathostomin species may be primarily responsible for resistance to specific drugs like macrocyclic lactones and pyrantel.
  • This finding challenges the assumption that resistance in cyathostomins is a general characteristic across species.
  • Understanding which species are resistant can help in developing more targeted parasite control strategies and could influence future drug development and usage protocols.
  • Further research may explore whether these findings apply to cyathostomin populations beyond the studied studs and regions.

Cite This Article

APA
Bull KE, Hodgkinson J, Allen K, Poissant J, Peachey LE. (2024). Quantitative DNA metabarcoding reveals species composition of a macrocyclic lactone and pyrantel resistant cyathostomin population in the UK. Int J Parasitol Drugs Drug Resist, 27, 100576. https://doi.org/10.1016/j.ijpddr.2024.100576

Publication

International journal for parasitology. Drugs and drug resistance
ISSN: 2211-3207
NlmUniqueID: 101576715
Country: Netherlands
Language: English
Volume: 27
Pages: 100576
PII: 100576

Researcher Affiliations

Bull, K E
  • Bristol Veterinary School, University of Bristol, Bristol, BS40 5DU, UK. Electronic address: katie.bull@bristol.ac.uk.
Hodgkinson, J
  • Department of Infection and Microbiome, Institute of Infection, Veterinary and Ecological Sciences, Leahurst Campus, University of Liverpool, Neston, CH64 7TE, UK.
Allen, K
  • Bristol Veterinary School, University of Bristol, Bristol, BS40 5DU, UK.
Poissant, J
  • Faculty of Veterinary Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.
Peachey, L E
  • Bristol Veterinary School, University of Bristol, Bristol, BS40 5DU, UK.

MeSH Terms

  • Animals
  • Horses
  • Anthelmintics / pharmacology
  • Pyrantel / pharmacology
  • Strongyloidea / drug effects
  • Strongyloidea / genetics
  • Strongyloidea / classification
  • United Kingdom / epidemiology
  • Feces / parasitology
  • Parasite Egg Count
  • DNA Barcoding, Taxonomic
  • Drug Resistance / genetics
  • Lactones / pharmacology
  • Strongyle Infections, Equine / parasitology
  • Strongyle Infections, Equine / drug therapy
  • Ivermectin / pharmacology
  • Horse Diseases / parasitology
  • Horse Diseases / drug therapy
  • Macrolides

Conflict of Interest Statement

Declaration of competing interest None.

References

This article includes 49 references
  1. Abbas G., Ghafar A., Bauquier J., Beasley A., Ling E., Gauci C.G., El-Hage C., Wilkes E.J.A., McConnell E., Carrigan P., Cudmore L., Hurley J., Beveridge I., Nielsen M.K., Stevenson M.A., Jacobson C., Hughes K.J., Jabbar A.. Prevalence and diversity of ascarid and strongylid nematodes in Australian Thoroughbred horses using next-generation sequencing and bioinformatic tools.. Vet. Parsitol. 2023;323.
    pubmed: 37844388
  2. Abbas G., Ghafar A., Hurley J., Bauquier J., Beasley A., Wilkes E.J.A., Jacobson C., El-Hage C., Cudmore L., Carrigan P., Tennent-Brown B., Gauci C.G., Nielsen M.K., Hughes K.J., Beveridge I., Jabbar A.. Cyathostomin resistance to moxidectin and combinations of anthelmintics in Australian horses.. Parasites Vectors 2021;14:597.
    pmc: PMC8645149pubmed: 34863271
  3. Abbas G., Ghafar A., McConnell E., Beasley A., Bauquier J., Wilkes E.J.A., El-Hage C., Carrigan P., Cudmore L., Hurley J., Gauci C.G., Beveridge I., Ling E., Jacobson C., Stevenson M.A., Nielsen M.K., Hughes K.J., Jabbar A.. A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses.. J. Parasitol. Drugs Drug Resist. 2024;24.
    pmc: PMC10757041pubmed: 38064906
  4. Avramenko R.W., Redman E.M., Lewis R., Yazwinski T.A., Wasmuth J.D., Gilleard J.S.. Exploring the gastrointestinal “nemabiome”: deep amplicon sequencing to quantify the species composition of parasitic nematode communities.. PLoS One 2015;10.
    pmc: PMC4668017pubmed: 26630572
  5. Bellaw J.L., Nielsen M.K.. Meta-analysis of cyathostomin species-specific prevalence and relative abundance in domestic horses from 1975–2020: emphasis on geographical region and specimen collection method.. Parasites Vectors 2020;13:509.
    pmc: PMC7552500pubmed: 33046130
  6. Bull K.E., Allen K.J., Hodgkinson J.E., Peachey L.E.. The first report of macrocyclic lactone resistant cyathostomins in the UK.. J. Parasitol. Drugs Drug Resist. 2023;21:125–130.
    pmc: PMC10036890pubmed: 36940551
  7. Byrne O., Gangotia D., Crowley J., Zintl A., Kiser L., Boxall O., McSweeney D., O'Neill F., Dunne S., Lamb B.R., Walshe N., Mulcahy G.. Molecular species determination of cyathostomins from horses in Ireland.. Vet. Parasitol. 2024;328.
    pubmed: 38547830
  8. Callahan B.J., McMurdie P.J., Rosen M.J., Han A.W., Johnson A.J.A., Holmes S.P.. DADA2: high-resolution sample inference from Illumina amplicon data.. Nat. Methods 2016;13:581–583.
    pmc: PMC4927377pubmed: 27214047
  9. Canever R.J., Braga P.R.C., Boeckh A., Grycajuck M., Bier D., Molento M.B.. Lack of Cyathostomin sp. reduction after anthelmintic treatment in horses in Brazil.. Vet. Parasitol. 2013;194:35–39.
    pubmed: 23318166
  10. Corning S.. Equine cyathostomins: a review of biology, clinical significance and therapy.. Parasites Vectors 2009;2:S1.
    pmc: PMC2751837pubmed: 19778462
  11. Cwiklinski K., Kooyman F.N., Van Doorn D.C., Matthews J.B., Hodgkinson J.E.. New insights into sequence variation in the IGS region of 21 cyathostomin species and the implication for molecular identification.. Parasitology 2012;139:1063–1073.
    pubmed: 22717256
  12. Dunn A.M.. Veterinary Helminthology.. .
  13. Gasser R.B., Bott N.J., Chilton N.B., Hunt P., Beveridge I.. Toward practical, DNA-based diagnostic methods for parasitic nematodes of livestock — bionomic and biotechnological implications.. Biotechnol. Adv. 2008;26:325–334.
    pubmed: 18502076
  14. Halvarsson P., Grandi G., Hägglund S., Höglund J.. Gastrointestinal parasite community structure in horses after the introduction of selective anthelmintic treatment strategies.. Vet. Parasitol. 2024;326.
    pubmed: 38218052
  15. Hamad M.H., Islam S.I., Jitsamai W., Chinkangsadarn T., Naraporn D., Ouisuwan S., Taweethavonsawat P.. Metabarcoding study to reveal the structural community of strongylid nematodes in domesticated horses in Thailand.. BMC Vet. Res. 2024;20:70.
    pmc: PMC10893705pubmed: 38395874
  16. Hedberg Alm Y, Halvarsson P, Martin F, Osterman-Lind E, Törngren V, Tydén E. Demonstration of reduced efficacy against cyathostomins without change in species composition after pyrantel embonate treatment in Swedish equine establishments.. J. Parasitol. Drugs Drug Resist. 2023;23:78–86.
    pmc: PMC10690405pubmed: 37979235
  17. Hodgkinson J.E., Freeman K.L., Lichtenfels J.R., Palfreman S., Love S, Matthews J.B.. Identification of strongyle eggs from anthelmintic-treated horses using a PCR-ELISA based on intergenic DNA sequences.. Parasitol. Res. 2005;95:287–292.
    pubmed: 15682337
  18. Hodgkinson J.E., Lichtenfels J.R., Mair T.S., Cripps P., Freeman K.L., Ramsey Y.H., Love S, Matthews J.B.. A PCR–ELISA for the identification of cyathostomin fourth-stage larvae from clinical cases of larval cyathostominosis.. J. Parasitol. 2003;33:1427–1435.
    pubmed: 14527525
  19. Ionita M., Howe D.K., Lyons E.T., Tolliver S.C., Kaplan R.M., Mitrea I.L., Yeargan M. Use of a reverse line blot assay to survey small strongyle (Strongylida: cyathostominae) populations in horses before and after treatment with ivermectin.. Vet. Parasitol. 2010;168:332–337.
    pubmed: 20045254
  20. Kaplan R.M., Denwood M.J., Nielsen M.K., Thamsborg S.M., Torgerson P.R., Gilleard J.S., Dobson R.J., Vercruysse J., Levecke B. World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guideline for diagnosing anthelmintic resistance using the faecal egg count reduction test in ruminants, horses and swine.. Vet. Parasitol. 2023;318.
    pubmed: 37121092
  21. Kuzmina Т., Zvegintsova N.S., Yasynetska N.I., Kharchenko V.A.. Anthelmintic resistance in strongylids (nematoda: strongylidae) parasitizing wild and domestic equids in the askania nova biosphere reserve, Ukraine.. Ann. Parasitol. 2020;66:49–60.
    pubmed: 32198995
  22. Lawson A.L., Malalana F., Mair T.S.. Larval cyathostominosis: clinicopathological data and treatment outcomes of 38 hospitalised horses (2009–2020). Equine Vet. Educ. 2023;35:424–435.
  23. Lichtenfels J.R., Kharchenko V.A., Dvojnos G.M.. Illustrated identification keys to strongylid parasites (Strongylidae: nematoda) of horses, zebras and asses (Equidae). Vet. Parasitol. 2008;156:4–161.
    pubmed: 18603375
  24. Love S., Murphy D., Mellor D.. Pathogenicity of cyathostome infection.. Vet. Parasitol. 1999;85:113–121.
    pubmed: 10485358
  25. Lyons E.T., Drudge J.H., Tolliver S.C.. Larval cyathostomiasis.. Vet. Clin. N. Am. Equine Pract. 2000;16:501–513.
    pubmed: 11219346
  26. Martin M.. CUTADAPT removes adapter sequences from high-throughput sequencing reads.. EMBnet. J. 2011;17:10–12.
  27. Merlin A., Larcher N., Vallé-Casuso J.C.. The first report of triple anthelmintic resistance on a French Thoroughbred stud farm.. J. Parasitol. Drugs Drug Resist. 2024;24.
    pmc: PMC10910056pubmed: 38422764
  28. Mitchell C.J., O'Sullivan C.M., Pinloche E., Wilkinson T., Morphew R.M., McEwan N.R.. Using next-generation sequencing to determine diversity of horse intestinal worms: identifying the equine 'nemabiome'.. J. Equine Sci. 2019;30:1–5.
    pmc: PMC6445754pubmed: 30944540
  29. Molena R.A., Peachey L.E., Di Cesare A., Traversa D., Cantacessi C.. Cyathostomine egg reappearance period following ivermectin treatment in a cohort of UK Thoroughbreds.. Parasites Vectors. 2018;11:61.
    pmc: PMC5785887pubmed: 29370872
  30. Morariu S., Mederle N., Badea C., Dărăbuş G., Ferrari N., Genchi C.. The prevalence, abundance and distribution of cyathostomins (small stongyles) in horses from Western Romania.. Vet. Parasitol. 2016;223:205–209.
    pubmed: 27198801
  31. Nielsen M.K.. Anthelmintic resistance in equine nematodes: current status and emerging trends.. J. Parasitol. Drugs Drug Resist. 2022;20:76–88.
    pmc: PMC9630620pubmed: 36342004
  32. Nielsen M.K., Banahan M., Kaplan R.M.. Importation of macrocyclic lactone resistant cyathostomins on a US thoroughbred farm.. J. Parasitol. Drugs Drug Resist. 2020;14:99–104.
    pmc: PMC7548974pubmed: 33022574
  33. Nielsen M.K., Steuer A.E., Anderson H.P., Gavriliuc S., Carpenter A.B., Redman E.M., Gilleard J.S., Reinemeyer C.R., Poissant J.. Shortened egg reappearance periods of equine cyathostomins following ivermectin or moxidectin treatment: morphological and molecular investigation of efficacy and species composition.. J. Parasitol. Drugs Drug Resist. 2022;52:787–798.
    pubmed: 36244428
  34. Peachey L.E., Pinchbeck G.L., Matthews J.B., Burden F.A., Lespine A., von Samson-Himmelstjerna G., Krücken J., Hodgkinson J.E.. P-glycoproteins play a role in ivermectin resistance in cyathostomins.. J. Parasitol. Drugs Drug Resist. 2017;7:388–398.
    pmc: PMC5681340pubmed: 29121562
  35. Poissant J., Gavriliuc S., Bellaw J., Redman E.M., Avramenko R.W., Robinson D., Workentine M.L., Shury T.K., Jenkins E.J., McLoughlin P.D., Nielsen M.K., Gilleard J.S.. A repeatable and quantitative DNA metabarcoding assay to characterize mixed strongyle infections in horses.. J. Parasitol. 2021;51:183–192.
    pubmed: 33242465
  36. Reid S.W.J., Mair T.S., Hillyer M.H., Love S.. Epidemiological risk factors associated with a diagnosis of clinical cyathostomiasis in the horse.. Equine Vet. J. 1995;27:127–130.
    pubmed: 7607145
  37. Relf V.E., Lester H.E., Morgan E.R., Hodgkinson J.E., Matthews J.B.. Anthelmintic efficacy on UK Thoroughbred stud farms.. Int. J. Parasitol. 2014;44:507–514.
    pubmed: 24746779
  38. Sargison N., Chambers A., Chaudhry U., Costa Júnior L., Doyle S.R., Ehimiyein A., Evans M., Jennings A., Kelly R., Sargison F., Sinclair M., Zahid O.. Faecal egg counts and nemabiome metabarcoding highlight the genomic complexity of equine cyathostomin communities and provide insight into their dynamics in a Scottish native pony herd.. J. Parasitol. 2022;52:763–774.
    pubmed: 36208676
  39. Scare J.A., Leathwick D.M., Sauermann C.W., Lyons E.T., Steuer A.E., Jones B.A., Clark M., Nielsen M.K.. Dealing with double trouble: combination deworming against double-drug resistant cyathostomins.. J. Parasitol. Drugs Drug Resist. 2020;12:28–34.
    pmc: PMC7139983pubmed: 31883485
  40. Scare J.A., Lyons E.T., Wielgus K.M., Nielsen M.K.. Combination deworming for the control of double-resistant cyathostomin parasites - short and long term consequences.. Vet. Parasitol. 2018;251:112–118.
    pubmed: 29426466
  41. Stancampiano L., Gras L.M., Poglayen G.. Spatial niche competition among helminth parasites in horse's large intestine.. Vet. Parasitol. 2010;170:88–95.
    pubmed: 20153115
  42. Team R.C.. R: A Language and Environment for Statistical Computing.. 2023.
  43. Torgerson P.R., Paul M., Furrer R.. Evaluating faecal egg count reduction using a specifically designed package “eggCounts” in R and a user friendly web interface.. J. Parasitol. 2014;44:299–303.
    pubmed: 24556564
  44. Traversa D., Iorio R., Klei T.R., Kharchenko V.A., Gawor J., Otranto D., Sparagano O.A.E.. New method for simultaneous species-specific identification of equine strongyles (nematoda, strongylida) by reverse line blot hybridization.. J. Clin. Microbiol. 2007;45:2937.
    pmc: PMC2045237pubmed: 17626168
  45. Traversa D., von Samson-Himmelstjerna G., Demeler J., Milillo P., Schürmann S., Barnes H., Otranto D., Perrucci S., di Regalbono A.F., Beraldo P., Boeckh A., Cobb R.. Anthelmintic resistance in cyathostomin populations from horse yards in Italy, United Kingdom and Germany.. Parasites Vectors. 2009;2:S2.
    pmc: PMC2751838pubmed: 19778463
  46. Wang C., Torgerson P.R., Kaplan R.M., George M.M., Furrer R.. Modelling anthelmintic resistance by extending eggCounts package to allow individual efficacy.. J. Parasitol. Drugs Drug Resist. 2018;8:386–393.
    pmc: PMC6091319pubmed: 30103206
  47. Wickham H.. Elegant Graphics for Data Analysis.. 2016.
  48. Wickham H., Vaughan D., Girlich M.. Tidyr: tidy messy data.. 2024.
  49. Wright E.S., Vetsigian K.H.. Quality filtering of Illumina index reads mitigates sample cross-talk.. BMC Genom. 2016;17:876.
    pmc: PMC5097354pubmed: 27814679

Citations

This article has been cited 5 times.
  1. Klass LG, Krücken J, Mbedi S, Sparmann S, Schenk T, Andreotti S, von Samson-Himmelstjerna G. Characterizing mixed strongyle infections in foals and broodmares using cytochrome c oxidase subunit I deep amplicon sequencing.. Parasit Vectors 2026 Jan 3;19(1):65.
    doi: 10.1186/s13071-025-07192-1pubmed: 41484633google scholar: lookup
  2. Mohtasebi S, Ahn S, Karimi M, Saberi M, Gilleard JS, Poissant J. Enhanced detection of equine strongyles: Insights from morphological and nemabiome metabarcoding approaches in northern Iran.. Equine Vet J 2026 Mar;58(2):508-522.
    doi: 10.1111/evj.70120pubmed: 41316832google scholar: lookup
  3. Abbas G, Nielsen MK, E-Hage C, Ghafar A, Beveridge I, Bauquier J, Beasley A, Wilkes EJA, Carrigan P, Cudmore L, Jacobson C, Hughes KJ, Jabbar A. Recent advances in intestinal helminth parasites of horses in the Asia-Pacific region: Current trends, challenges and future directions.. Int J Parasitol Drugs Drug Resist 2025 Dec;29:100622.
    doi: 10.1016/j.ijpddr.2025.100622pubmed: 41135277google scholar: lookup
  4. Ochigbo GO, Ahn S, Belhumeur KA, Poissant J, Rosa BV. Nemabiome sequencing reveals seasonal and age associated patterns of strongyle infection and high prevalence of Strongylus vulgaris in Alberta feral horses.. Int J Parasitol Parasites Wildl 2025 Aug;27:101091.
    doi: 10.1016/j.ijppaw.2025.101091pubmed: 40524829google scholar: lookup
  5. Nielsen MK, Pyatt A, Perrett J, Tydén E, van Doorn D, Pihl TH, Schmidt JS, von Samson-Himmelstjerna G, Beasley A, Abbas G, Jabbar A. Global equine parasite control guidelines: Consensus or confusion?. Int J Parasitol Drugs Drug Resist 2025 Aug;28:100600.
    doi: 10.1016/j.ijpddr.2025.100600pubmed: 40472642google scholar: lookup
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