Identification of foals infected with Parascaris equorum apparently resistant to ivermectin.
Abstract: During September 2002, routine fecal examinations performed on 16 Thoroughbred foals residing on a farm outside Toronto, Ontario, Canada, revealed low to moderate numbers of Parascaris equorum eggs in feces from 9 of the 16. All foals were then treated with ivermectin at a dose of 220 to 280 microg/kg (100 to 127 microg/lb), p.o., and fecal egg counts were repeated 12 days later. Fecal P. equorum egg counts increased between the first and second fecal examination in 7 foals, were unchanged in 1, and decreased in 5. Fecal samples were collected 13 days after treatment from 21 additional foals that had been treated with ivermectin at the same dose, and P. equorum eggs were detected in 12 of the 21. For all 37 foals, high P. equorum egg counts (> or = 100 eggs/g of feces) 12 to 13 days after ivermectin treatment were significantly more likely in foals that had been regularly treated with ivermectin since birth and permanently resided on the farm, compared with foals that had been treated with other anthelmintics or had an unknown deworming history. Collectively, these data suggested that P. equorum in these foals was resistant to ivermectin administered at the recommended dose.
Publication Date: 2003-08-22 PubMed ID: 12930086DOI: 10.2460/javma.2003.223.482Google Scholar: Lookup
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Summary
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The research article discusses the identification of young horses (foals) found to be infected with a parasitic worm (Parascaris equorum), showing the parasite’s strong resistance to the commonly used drug ivermectin.
Study Purpose and Approach
- The study aimed to identify any issues with the effectiveness of ivermectin in treating Parascaris equorum infections amongst a group of Thoroughbred foals in Ontario, Canada.
- These foals were subjected to routine fecal examinations, with the presence of P. equorum eggs indicating an active infection.
- After ivermectin treatment, the count of P. equorum eggs was repeated to determine the treatment’s effectiveness.
Findings
- From the initial group of 37 foals, P. equorum eggs were found in the feces of 9 foals.
- After administering ivermectin and conducting a second fecal test, P. equorum egg counts increased in 7 out of the 9 foals, remained unchanged in one, and decreased in five foals.
- In an additional group of 21 foals treated with ivermectin, P. equorum eggs were detected in 12 of them 13 days after treatment.
Conclusion
- The results suggested that the P. equorum parasites in these foals were resistant to ivermectin when administered at the recommended dosage.
- It was observed that high P. equorum egg counts following ivermectin treatment were more likely in those foals that had been regularly treated with ivermectin from birth and those permanently residing on the farm, compared with foals treated with other anthelmintics or with an unknown deworming history.
- The study thus indicates a potential issue in the widespread use of ivermectin as a treatment for this infection, suggesting the need for further research into alternative treatments and potential causes for this resistance.
Cite This Article
APA
Hearn FP, Peregrine AS.
(2003).
Identification of foals infected with Parascaris equorum apparently resistant to ivermectin.
J Am Vet Med Assoc, 223(4), 482-455.
https://doi.org/10.2460/javma.2003.223.482 Publication
Researcher Affiliations
- Hearn Veterinary Services, 713558 RR1, Orangeville, ON L9W 2Y8, Canada.
MeSH Terms
- Animals
- Animals, Newborn
- Anthelmintics / pharmacology
- Anthelmintics / therapeutic use
- Ascaridida Infections / drug therapy
- Ascaridida Infections / parasitology
- Ascaridida Infections / veterinary
- Ascaridoidea / drug effects
- Drug Resistance
- Feces / parasitology
- Horse Diseases / drug therapy
- Horse Diseases / parasitology
- Horses
- Intestinal Diseases, Parasitic / drug therapy
- Intestinal Diseases, Parasitic / veterinary
- Ivermectin / pharmacology
- Ivermectin / therapeutic use
- Ontario
- Parasite Egg Count / veterinary
- Parasitic Sensitivity Tests / veterinary
Citations
This article has been cited 17 times.- Cain JL, Norris JK, Ripley NE, Suri P, Finnerty CA, Gravatte HS, Nielsen MK. The microbial community associated with Parascaris spp. infecting juvenile horses.. Parasit Vectors 2022 Nov 4;15(1):408.
- Cain JL, Nielsen MK. The equine ascarids: resuscitating historic model organisms for modern purposes.. Parasitol Res 2022 Oct;121(10):2775-2791.
- Matthews JB. Anthelmintic resistance in equine nematodes.. Int J Parasitol Drugs Drug Resist 2014 Dec;4(3):310-5.
- Lyons ET, Tolliver SC, Kuzmina TA. Investigation of strongyle EPG values in horse mares relative to known age, number positive, and level of egg shedding in field studies on 26 farms in Central Kentucky (2010-2011).. Parasitol Res 2012 Jun;110(6):2237-45.
- Lyons ET, Tolliver SC, Kuzmina TA, Collins SS. Further evaluation in field tests of the activity of three anthelmintics (fenbendazole, oxibendazole, and pyrantel pamoate) against the ascarid Parascaris equorum in horse foals on eight farms in Central Kentucky (2009-2010).. Parasitol Res 2011 Oct;109(4):1193-7.
- Lind EO, Christensson D. Anthelmintic efficacy on Parascaris equorum in foals on Swedish studs.. Acta Vet Scand 2009 Nov 22;51(1):45.
- Reinemeyer CR. Diagnosis and control of anthelmintic-resistant Parascaris equorum.. Parasit Vectors 2009 Sep 25;2 Suppl 2(Suppl 2):S8.
- Nielsen MK. Restrictions of anthelmintic usage: perspectives and potential consequences.. Parasit Vectors 2009 Sep 25;2 Suppl 2(Suppl 2):S7.
- Cobb R, Boeckh A. Moxidectin: a review of chemistry, pharmacokinetics and use in horses.. Parasit Vectors 2009 Sep 25;2 Suppl 2(Suppl 2):S5.
- Physick-Sheard PW, Peregrine AS, Hearn FP. Equine anthelmintics by prescription only?. Can Vet J 2009 May;50(5):449.
- Lyons ET, Tolliver SC, Collins SS. Probable reason why small strongyle EPG counts are returning "early" after ivermectin treatment of horses on a farm in Central Kentucky.. Parasitol Res 2009 Feb;104(3):569-74.
- Lyons ET, Tolliver SC, Ionita M, Collins SS. Evaluation of parasiticidal activity of fenbendazole, ivermectin, oxibendazole, and pyrantel pamoate in horse foals with emphasis on ascarids (Parascaris equorum) in field studies on five farms in Central Kentucky in 2007.. Parasitol Res 2008 Jul;103(2):287-91.
- Slocombe JO, Coté JF, de Gannes RV. The persistence of benzimidazole-resistant cyathostomes on horse farms in Ontario over 10 years and the effectiveness of ivermectin and moxidectin against these resistant strains.. Can Vet J 2008 Jan;49(1):56-60.
- Lind EO, Rautalinko E, Uggla A, Waller PJ, Morrison DA, Höglund J. Parasite control practices on Swedish horse farms.. Acta Vet Scand 2007 Sep 26;49(1):25.
- Lyons ET, Tolliver SC, Rathgeber RA, Collins SS. Parasite field study in central Kentucky on thoroughbred foals (born in 2004) treated with pyrantel tartrate daily and other parasiticides periodically.. Parasitol Res 2007 Feb;100(3):473-8.
- Lyons ET, Tolliver SC, Collins SS. Field studies on endoparasites of Thoroughbred foals on seven farms in central Kentucky in 2004.. Parasitol Res 2006 Apr;98(5):496-500.
- Lyons ET, Tolliver SC. Prevalence of parasite eggs (Strongyloides westeri, Parascaris equorum, and strongyles) and oocysts (Emeria leuckarti) in the feces of Thoroughbred foals on 14 farms in central Kentucky in 2003.. Parasitol Res 2004 Mar;92(5):400-4.
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