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Home / Equine Research Bank / Equine Vet J / Reasons to be fearful? Rising proportions of positive faecal...
Equine veterinary journal2025; doi: 10.1111/evj.14478

Reasons to be fearful? Rising proportions of positive faecal worm egg counts among UK horses (2007-2023).

Abstract: Anthelmintic resistance (AR) threatens effective equine parasite control. Quarterly data summaries from faecal worm egg count testing (FWECT) performed by UK laboratories have appeared in Equine Quarterly Disease Surveillance Reports (EQDSR) since 2007, but have not previously been assessed. Objective: To assess strongyle FWECT methods and thresholds used by UK laboratories. To investigate factors associated with quarterly laboratory FWECT positivity rates between 2007 and 2023. Methods: Laboratory surveys and analysis of laboratory summary data. Methods: Laboratories were surveyed in Q3 2018 and again in Q4 2023. Proportions of FWECTs reported positive (PTP) each quarter by individual laboratories between 2007 and 2023 were analysed using multiple mixed-effects linear regression, evaluating laboratory-level random-effects and fixed-effects variables for ordered categories of FWECT-thresholds, year-quarters and consecutive year groups. Results: Ten laboratories responded in 2018 and 13 laboratories in 2023. Samples were commonly reported positive at >0 to <100 eggs per gram (epg) and ≥200 epg. Regression modelling of 1190 EQDSR submissions confirmed significantly decreased PTP for thresholds ≥100 to <300 epg (level-2: -12.0%, p = 0.03), ≥300 epg (level-3: -18.0%, p = 0.03) and when thresholds were not specified (level-4: -12.2%, p = 0.0), relative to level-1 baseline (>0 to <100 epg). No significant seasonal variation in PTP between year-quarters was evident. Overall, controlling for between-laboratory variation and FWECT thresholds, there remained evidence for a significant gradient in increasing PTP over the study period relative to baseline (2007-2009). There were increases in PTP of +6.9% in 2010-2011 (p < 0.001), +10.1% in 2012-2013 (p < 0.001), +14.1% in 2014-2015 (p < 0.001), +16.0% in 2016-2017 (p < 0.001), +15.6% in 2018-2019 (p < 0.001), +17.1% in 2020-2021 (p < 0.001) and +18.9% in 2022-2023 (p < 0.001). Conclusions: Survey responses were limited and most laboratories' FWECT thresholds were not known. Conclusions: Controlling for laboratories and FWECT thresholds there was strong residual evidence from FWECT summary data for increasing egg counts in UK horses between 2007 and 2023.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2025-01-22 PubMed ID: 39840839DOI: 10.1111/evj.14478Google Scholar: Lookup
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  • Journal Article

Summary

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The research paper provides an analysis of the increasing rates of faecal worm egg positivity from 2007 to 2023 in horse samples across the UK laboratories, scrutinized through faecal worm egg count testing (FWECT), an indicator of anthelmintic resistance (AR).

Objective and Methods of the Study

  • The paper aims to assess strongyle FWECT methods and thresholds used by UK laboratories as well as to explore factors tied to the FWECT positivity rates on a quarterly basis from 2007 to 2023.
  • The study employed laboratory surveys as well as analysis of the laboratories’ summary data.
  • The surveys were conducted twice – once in the third quarter of 2018 and then in the fourth quarter of 2023.
  • The proportions of FWECTs reported positive (PTP) each quarter by individual laboratories in the given timeframe were analyzed using multiple mixed-effects linear regression.
  • Through this regression, the study evaluated laboratory-level random-effects and fixed-effects variables for ordered categories of FWECT-thresholds, year-quarters, and consecutive year groups.

Results of the Analysis

  • In both the surveys of 2018 and 2023, 10 and 13 laboratories responded respectively.
  • The samples were mainly reported positive at >0 to <100 eggs per gram (epg) and ≥200 epg.
  • The regression modeling of 1190 EQDSR submissions confirmed a significant decrease in PTP for thresholds ≥100 to 0 to <100 epg).
  • No significant seasonal variation in PTP between year-quarters was found.

Overarching Trends Over the Years

  • Controlling for between-laboratory variation and FWECT thresholds, the research found evidence for a significant gradient in PTP’s increase over the study period relative to baseline (2007-2009).
  • Documented PTP increases during the consecutive two-year periods from 2010-2011 to 2022-2023 suggested an increasing trend in egg counts in UK horses over the years.

Conclusions

  • The researchers acknowledged the limited responses to the surveys and the fact that most laboratories’ FWECT thresholds were not specified.
  • However, the research highlights that analysing FWECT summary data, provides evidence of increasing egg counts in UK horses between 2007 and 2023, indicating a potential rise in anthelmintic resistance in these animals.

Cite This Article

APA
Whitlock F, van Dijk J, Hodgkinson JE, Grewar JD, Newton JR. (2025). Reasons to be fearful? Rising proportions of positive faecal worm egg counts among UK horses (2007-2023). Equine Vet J. https://doi.org/10.1111/evj.14478

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Whitlock, Fleur
  • Equine Infectious Disease Surveillance (EIDS), Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.
van Dijk, Jan
  • Animal Health Vision International, Taunton, UK.
Hodgkinson, Jane E
  • Institute of infection, Veterinary and Ecological Sciences, University of Liverpool, Neston, UK.
Grewar, John Duncan
  • jDATA (Pty) Ltd, Sandbaai, South Africa.
Newton, J Richard
  • Equine Infectious Disease Surveillance (EIDS), Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.

References

This article includes 41 references
  1. Cai E, Wu R, Wu Y, Gao Y, Zhu Y, Li J. A systematic review and meta‐analysis on the current status of anthelmintic resistance in equine nematodes: a global perspective.. Mol Biochem Parasitol 2024;257:111600.
    doi: 10.1016/j.molbiopara.2023.111600google scholar: lookup
  2. Peregrine AS, Molento MB, Kaplan RM, Nielsen MK. Anthelmintic resistance in important parasites of horses: does it really matter?. Vet Parasitol 2014;201(1–2):1–8.
    doi: 10.1016/j.vetpar.2014.01.004google scholar: lookup
  3. Nielsen MK. Anthelmintic resistance in equine nematodes: current status and emerging trends.. Int J Parasitol Drugs Drug Resist 2022;20:76–88.
    doi: 10.1016/j.ijpddr.2022.10.005google scholar: lookup
  4. Reinemeyer CR. Diagnosis and control of anthelmintic‐resistant Parascaris equorum.. Parasit Vectors 2009;2:2.
    doi: 10.1186/1756-3305-2-s2-s8google scholar: lookup
  5. Kaplan RM, Vidyashankar AN. An inconvenient truth: global worming and anthelmintic resistance.. Vet Parasitol 2012;186(1–2):70–78.
    doi: 10.1016/j.vetpar.2011.11.048google scholar: lookup
  6. CANTER. Controlling ANTiparasitic Resistance in Equines Responsibly. https://canterforhorses.org.uk/
  7. EIDS. Equine Quarterly Disease Surveillance Report, Produced by Equine Infectious Disease Surveillance (EIDS). https://equinesurveillance.org/
  8. Becher AM, Mahling M, Nielsen MK, Pfister K. Selective anthelmintic therapy of horses in the Federal states of Bavaria (Germany) and Salzburg (Austria): an investigation into strongyle egg shedding consistency.. Vet Parasitol 2010;171(1–2):116–122.
    doi: 10.1016/j.vetpar.2010.03.001google scholar: lookup
  9. Nielsen MK, Haaning N, Olsen SN. Strongyle egg shedding consistency in horses on farms using selective therapy in Denmark.. Vet Parasitol 2006;135(3–4):333–335.
    doi: 10.1016/j.vetpar.2005.09.010google scholar: lookup
  10. Duncan JL. Field studies on the epidemiology of mixed strongyle infection in the horse.. Vet Rec 1974;94(15):337–345.
    doi: 10.1136/vr.94.15.337google scholar: lookup
  11. Nielsen MK, Baptiste KE, Tolliver SC, Collins SS, Lyons ET. Analysis of multiyear studies in horses in Kentucky to ascertain whether counts of eggs and larvae per gram of feces are reliable indicators of numbers of strongyles and ascarids present.. Vet Parasitol 2010;174(1–2):77–84.
    doi: 10.1016/j.vetpar.2010.08.007google scholar: lookup
  12. Van Wyk JA. Refugia – overlooked as perhaps the most potent factor concerning the development of anthelmintic resistance.. Onderstepoort J Vet Res 2001;68(1):55–67.
  13. Gomez HH, Georgi JR. Equine helminth infections: control by selective chemotherapy.. Equine Vet J 1991;23(3):198–200.
    doi: 10.1111/j.2042-3306.1991.tb02754.xgoogle scholar: lookup
  14. Duncan JL, Love S. Preliminary observations on an alternative strategy for the control of horse strongyles.. Equine Vet J 1991;23(3):226–228.
    doi: 10.1111/j.2042-3306.1991.tb02762.xgoogle scholar: lookup
  15. Lester HE, Matthews JB. Faecal worm egg count analysis for targeting anthelmintic treatment in horses: points to consider.. Equine Vet J 2014;46(2):139–145.
    doi: 10.1111/evj.12199google scholar: lookup
  16. Gordon HM, Whitlock AV. A new technique for counting nematode eggs in sheep feces.. J Council Sci Ind Res 1939;12(1):50–52.
  17. Whitlock HV. Some modifications of the McMaster helminth egg‐counting technique and apparatus.. J Council Sci Ind Res 1948;21:177–180.
  18. Zoetis Ovactec Plus. https://www2.zoetis.nl/diersoort/paarden/products/ovatec-plus
  19. Ovacyte. https://www.telenostic.com/about-ovacyte/
  20. Mfitilodze MW, Hutchinson GW. The site distribution of adult strongyle parasites in the large intestines of horses in tropical Australia.. Int J Parasitol 1985;15(3):313–319.
    doi: 10.1016/0020-7519(85)90069-4google scholar: lookup
  21. Sallé G, Guillot J, Tapprest J, Foucher N, Sevin C, Laugier C. Compilation of 29 years of postmortem examinations identifies major shifts in equine parasite prevalence from 2000 onwards.. Int J Parasitol 2020;50(2):125–132.
    doi: 10.1016/j.ijpara.2019.11.004google scholar: lookup
  22. Dowdall SMJ, Matthews JB, Mair T, Murphy D, Love S, Proudman CJ. Antigen‐specific IgG(T) responses in natural and experimental cyathostominae infection in horses.. Vet Parasitol 2002;106(3):225–242.
    doi: 10.1016/s0304-4017(02)00085-7google scholar: lookup
  23. Roeber F, Morrison A, Casaert S, Smith L, Claerebout E, Skuce P. Multiplexed‐tandem PCR for the specific diagnosis of gastrointestinal nematode infections in sheep: an European validation study.. Parasit Vectors 2017;10(1):226.
    doi: 10.1186/s13071-017-2165-xgoogle scholar: lookup
  24. Reslova N, Skorpikova L, Kyrianova IA, Vadlejch J, Höglund J, Skuce P. The identification and semi‐quantitative assessment of gastrointestinal nematodes in faecal samples using multiplex real‐time PCR assays.. Parasit Vectors 2021;14(1):391.
    doi: 10.1186/s13071-021-04882-4google scholar: lookup
  25. Abbas G, Ghafar A, Beasley A, Stevenson MA, Bauquier J, Koehler AV. Understanding temporal and spatial distribution of intestinal nematodes of horses using faecal egg counts and DNA metabarcoding.. Vet Parasitol 2024;325:110094.
    doi: 10.1016/j.vetpar.2023.110094google scholar: lookup
  26. Kaplan RM, Denwood MJ, Nielsen MK, Thamsborg SM, Torgerson PR, Gilleard JS. 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;318:109936.
    doi: 10.1016/j.vetpar.2023.109936google scholar: lookup
  27. Lester H, Bartley D, Morgan E, Hodgkinson J, Matthews J. The spatial distribution of strongyle eggs in horse faeces.. J Equine Vet Sci 2012;32(10):S33–S34.
    doi: 10.1016/j.jevs.2012.08.077google scholar: lookup
  28. Nielsen MK, Vidyashankar AN, Andersen UV, DeLisi K, Pilegaard K, Kaplan RM. Effects of fecal collection and storage factors on strongylid egg counts in horses.. Vet Parasitol 2010;167(1):55–61.
    doi: 10.1016/j.vetpar.2009.09.043google scholar: lookup
  29. Rendle D, Austin C, Bowen M, Cameron I, Furtado T, Hodgkinson J. Equine de‐worming: a consensus on current best practice.. UK‐Vet Equine 2019;10.12968/ukve.2019.3.s.3:3–14.
  30. Rendle D, Hughes K, Bowen M, Bull K, Cameron I, Furtado T. BEVA primary care clinical guidelines: Equine parasite control.. Equine Vet J 2024;56(3):392–423.
    doi: 10.1111/evj.14036google scholar: lookup
  31. Geurden T, Olson ME, O'Handley RM, Schetters T, Bowman D, Vercruysse J. World Association for the Advancement of Veterinary Parasitology (WAAVP): guideline for the evaluation of drug efficacy against non‐coccidial gastrointestinal protozoa in livestock and companion animals.. Vet Parasitol 2014;204(3–4):81–86.
    doi: 10.1016/j.vetpar.2014.02.050google scholar: lookup
  32. Beasley AM, Kotze AC, Barnes TS, Coleman GT. Equine helminth prevalence and management practices on Australian properties as shown by coprological survey and written questionnaire.. Anim Prod Sci 2020;60(18):2131–2144.
    doi: 10.1071/an18378google scholar: lookup
  33. Sargison N, Chambers A, Chaudhry U, Costa Júnior L, Doyle SR, Ehimiyein A. 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.. Int J Parasitol 2022;52(12):763–774.
    doi: 10.1016/j.ijpara.2022.08.002google scholar: lookup
  34. Boelow H, Krücken J, von Samson‐Himmelstjerna G. Epidemiological study on factors influencing the occurrence of helminth eggs in horses in Germany based on sent‐in diagnostic samples.. Parasitol Res 2023;122(3):749–767.
    doi: 10.1007/s00436-022-07765-4google scholar: lookup
  35. Baudena MA, Chapman MR, French DD, Klei TR. Seasonal development and survival of equine cyathostome larvae on pasture in south Louisiana.. Vet Parasitol 2000;88(1–2):51–60.
    doi: 10.1016/s0304-4017(99)00198-3google scholar: lookup
  36. Ramsey YH, Christley RM, Matthews JB, Hodgkinson JE, McGoldrick J, Love S. Seasonal development of Cyathostominae larvae on pasture in a northern temperate region of the United Kingdom.. Vet Parasitol 2004;119(4):307–318.
    doi: 10.1016/j.vetpar.2003.11.014google scholar: lookup
  37. Taylor MA. SCOPS and COWS—worming it out of UK farmers.. Vet Parasitol 2012;186(1–2):65–69.
    doi: 10.1016/j.vetpar.2011.11.047google scholar: lookup
  38. Knapp‐Lawitzke F, von Samson‐Himmelstjerna G, Demeler J. Elevated temperatures and long drought periods have a negative impact on survival and fitness of strongylid third stage larvae.. Int J Parasitol 2016;46(4):229–237.
    doi: 10.1016/j.ijpara.2015.10.006google scholar: lookup
  39. Relf VE, Morgan ER, Hodgkinson JE, Matthews JB. Helminth egg excretion with regard to age, gender and management practices on UK Thoroughbred studs.. Parasitology 2013;140(5):641–652.
    doi: 10.1017/s0031182012001941google scholar: lookup
  40. Lester HE, Morgan ER, Hodgkinson JE, Matthews JB. Analysis of strongyle egg shedding consistency in horses and factors that affect it.. J Equine Vet Sci 2018;60:113–119.e1.
    doi: 10.1016/j.jevs.2017.04.006google scholar: lookup
  41. Wood EL, Matthews JB, Stephenson S, Slote M, Nussey DH. Variation in fecal egg counts in horses managed for conservation purposes: individual egg shedding consistency, age effects and seasonal variation.. Parasitology 2013;140(1):115–128.
    doi: 10.1017/s003118201200128xgoogle scholar: lookup
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