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International journal for parasitology. Drugs and drug resistance2023; 22; 96-101; doi: 10.1016/j.ijpddr.2023.06.002

Apparent treatment failure of praziquantel and pyrantel pamoate against anoplocephalid tapeworms.

Abstract: Anoplocephalid tapeworms are commonly occurring in grazing horses around the world. Two currently available anthelmintics have documented high efficacy against Anoplocephala perfoliata; praziquantel in various dosages ranging from 1.0 to 2.5 mg/kg and pyrantel pamoate administered at 13.2 mg base/kg. Anthelmintic resistance has not been reported in A. perfoliata, but anecdotal reports made during 2022 have suggested a possible loss of efficacy for both actives. This paper reports fecal egg count data from a Thoroughbred operation in Central Kentucky in 2023. Fifty-six yearlings were first dewormed with a combination of ivermectin (200 μg/kg) and praziquantel (1.5 mg/kg) and subsequently treated with pyrantel pamoate (13.2 mg base/kg). Fecal egg counts were determined at the day of treatment and again 14 days post-treatment. Two groups of mares (n = 39 and 45) were also treated with ivermectin/praziquantel and examined pre- and post-treatment. Low efficacy of ivermectin and pyrantel pamoate was demonstrated against strongylid parasites in the yearlings with mean Fecal Egg Count Reductions (FECRs) at 75.6% or below and upper 95% credible interval (CI) limits below 90% in all cases. Overall anti-cestodal FECR levels in the yearlings were 23.5% (95% CI: 11.2-48.0) for praziquantel and 50.9% (20.5-72.0) for pyrantel pamoate. Praziquantel eliminated anoplocephalid eggs from three of 17 yearlings, but another 5 yearlings went from negative to positive status following treatment. Pyrantel pamoate failed to eliminate anoplocephalid eggs from any of 14 treated tapeworm-positive yearlings. Nine of 84 mares tested positive for anoplocephalid eggs, and seven of these were still positive post praziquantel treatment. These findings sharply contrast data from historic field efficacy studies conducted for both actives and raise concern about anthelmintic resistance having possibly developed. This emphasizes the need for developing and refining antemortem methodologies for evaluating anti-cestodal treatment efficacy and for searching for possible alternative treatment options.
Copyright © 2023 The Author. Published by Elsevier Ltd.. All rights reserved.
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Publication Date: 2023-06-19 PubMed ID: 37354849PubMed Central: PMC10331019DOI: 10.1016/j.ijpddr.2023.06.002Google 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.

This research article examines the growing concern that two commonly used deworming drugs, praziquantel and pyrantel pamoate, might be losing their effectiveness in treating Anoplocephalid tapeworms in horses, based on a study conducted on a Thoroughbred farm in Central Kentucky.

Objectives and Methodology of the Study

  • The researchers set out to investigate anecdotal reports suggesting that anthelmintics praziquantel and pyrantel pamoate were losing efficacy against Anoplocephala perfoliata, a common tapeworm in horses.
  • Their research was conducted in a thoroughbred horse operation in Central Kentucky in 2023, involving 56 yearlings, and 2 groups of mares (one group with 39 members, the other with 45).
  • All subjects were initially treated with a drug combination of ivermectin and praziquantel, followed by a dose of pyrantel pamoate.
  • Fecal egg counts (FECs) were done before and 14 days after treatment, to assess the effectiveness of the administered anthelmintics.

Findings of the Study

  • The research demonstrated relatively low efficacy of ivermectin and pyrantel pamoate against strongylid parasites, with the average Fecal Egg Count Reduction (FECR) returning below 75.6% and credible interval limits not surpassing 90% in all trials.
  • Praziquantel and pyrantel pamoate showed even lower FECR levels in counteracting cestodal parasites, with respective effectiveness rates of 23.5% and 50.9%, both well below satisfaction.
  • The effectiveness of praziquantel was particularly concerning, eliminating tapeworm eggs in only 3 of 17 treated yearlings, even as 5 other yearlings transitioned from a negative to positive tapeworm status after treatment. Pyrantel pamoate fared worse; failing to purge any tapeworm eggs from the 14 treated yearlings.
  • The results were similarly worrying for the mares. Of the 84 tested, 9 showed tapeworm presence before treatment, and 7 of these remained tapeworm-positive even after administration of praziquantel.

Implications

  • The remarkably low efficacy of both anthelmintics in this study deviates sharply from historical data, raising concerns that tapeworms might be developing resistance to these treatments.
  • Consequentially, this calls for the development and refinement of antemortem methodologies for accurately evaluating anti-cestodal treatment efficacy. It also underlines the urgency and necessity for exploring alternative treatment options to counter potential anthelmintic resistance.

Cite This Article

APA
Nielsen MK. (2023). Apparent treatment failure of praziquantel and pyrantel pamoate against anoplocephalid tapeworms. Int J Parasitol Drugs Drug Resist, 22, 96-101. https://doi.org/10.1016/j.ijpddr.2023.06.002

Publication

International journal for parasitology. Drugs and drug resistance
ISSN: 2211-3207
NlmUniqueID: 101576715
Country: Netherlands
Language: English
Volume: 22
Pages: 96-101

Researcher Affiliations

Nielsen, M K
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, USA. Electronic address: martin.nielsen@uky.edu.

MeSH Terms

  • Animals
  • Horses
  • Female
  • Pyrantel Pamoate / therapeutic use
  • Praziquantel / therapeutic use
  • Ivermectin / therapeutic use
  • Horse Diseases / drug therapy
  • Horse Diseases / parasitology
  • Anthelmintics / therapeutic use
  • Cestoda
  • Treatment Failure
  • Feces / parasitology
  • Treatment Outcome
  • Parasite Egg Count / veterinary

Conflict of Interest Statement

Declaration of competing interest The author declares no conflicts of interest.

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