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Home / Equine Research Bank / Parasitol Res / Equine strongylids: Ivermectin efficacy and fecal egg sheddi...
Parasitology research2022; 121(6); 1691-1697; doi: 10.1007/s00436-022-07509-4

Equine strongylids: Ivermectin efficacy and fecal egg shedding patterns.

Abstract: Equine cyathostomins are ubiquitous in grazing horses around the world and a main target in parasite control programs. Anthelmintic resistance has been reported with increasing frequency in these parasites over the past decades, and recent findings of fulminant resistance to the macrocyclic lactone class have raised severe concerns. This study aimed to evaluate ivermectin efficacy in cohorts of yearlings and mares present on four different farms in Central Kentucky. Strongylid egg counts were determined with an automated egg counting system, and the percent fecal egg count reduction (FECR) was calculated using a hierarchical Bayesian analysis. Novel principles were used for classification of groups to either no signs of anthelmintic resistance, evidence of resistance, or inconclusive. Furthermore, an epidemiological analysis was conducted evaluating the possible influence of pregnancy status, time of foaling, and year of arrival on mare strongylid egg shedding levels. A total of 102 yearlings and 247 mares were enrolled in the study. Evidence of ivermectin resistance was documented in one group of yearlings with a mean FECR of 91.2% and a 95% credible interval of 84.0-95.8. The results from one mare group and one additional yearling group were deemed inconclusive, whereas the remaining five groups displayed no evidence of ivermectin resistance. Strongylid shedding in the mares was not positively associated with any of the evaluated factors. This study is the first to demonstrate ivermectin resistance in US bred horses, and the findings emphasize the need for routine monitoring of anthelmintic efficacy on horse farms.
© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
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Publication Date: 2022-04-06 PubMed ID: 35384503PubMed Central: 1316126DOI: 10.1007/s00436-022-07509-4Google Scholar: Lookup
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  • Journal Article

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.

The research article discusses a study that investigated the efficacy of ivermectin, a drug used to treat parasites in horses. The study found some evidence of resistance to the drug amongst the tested horses, suggesting that farming practices may need to evolve in response.

Objective and Method of the Study

  • The research aimed to evaluate the efficacy of ivermectin in treating equine cyathostomins, a common type of parasite in grazing horses.
  • This was carried out by testing cohorts of horses (yearlings and mares) from four different farms in Central Kentucky.
  • The horses were evaluated using a method known as fecal egg count reduction (FECR), which measures the number of parasite eggs in their feces before and after treatment with ivermectin.

Results and Findings

  • A total of 102 yearlings and 247 mares were enrolled in the study.
  • In one group of yearlings, the mean FECR was 91.2% – below the expected effectiveness of ivermectin – and their results fell within a 95% credible interval of 84.0-95.8%.
  • This suggests some level of resistance to ivermectin within this group.
  • The results for one group of mares and one additional group of yearlings was inconclusive, while the remaining five groups displayed no evidence of ivermectin resistance.
  • There was no clear correlation between the mares’ shedding of strongylid eggs – a sign of infection – and factors such as their pregnancy status, foaling time, or year of arrival at the farms.

Significance of the Research

  • This is the first study to demonstrate resistance to ivermectin in horses bred in the US.
  • The findings underscore the importance of ongoing monitoring to determine how effective anthelmintics (drugs used for treating parasitic worms) are on horse farms.
  • While resistance to ivermectin was only noted in one group, the possibility of resistance developing to this commonly-used treatment could have significant implications for equine health and farming practices.

Cite This Article

APA
Nielsen MK, Littman BA, Orzech SW, Ripley NE. (2022). Equine strongylids: Ivermectin efficacy and fecal egg shedding patterns. Parasitol Res, 121(6), 1691-1697. https://doi.org/10.1007/s00436-022-07509-4

Publication

Parasitology research
ISSN: 1432-1955
NlmUniqueID: 8703571
Country: Germany
Language: English
Volume: 121
Issue: 6
Pages: 1691-1697

Researcher Affiliations

Nielsen, Martin K
  • M. H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA. martin.nielsen@uky.edu.
Littman, Brooke A
  • College of Veterinary Medicine, University of California, Davis, CA, USA.
Orzech, Sierra W
  • College of Veterinary Medicine, University of Georgia, Athens, GA, USA.
Ripley, Nichol E
  • M. H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.

MeSH Terms

  • Animals
  • Anthelmintics / pharmacology
  • Anthelmintics / therapeutic use
  • Bayes Theorem
  • Drug Resistance
  • Feces / parasitology
  • Female
  • Horse Diseases / drug therapy
  • Horse Diseases / parasitology
  • Horses
  • Ivermectin / pharmacology
  • Ivermectin / therapeutic use
  • Parasite Egg Count / veterinary
  • Pregnancy

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