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First Report of Resistance to Ivermectin in Parascaris univalens in Iceland

Martin, Frida and Svansson, Vilhjalmur and Eydal, Matthias and Oddsdottir, Charlotta and Ernback, Maja and Persson, Isa and Tyden, Eva (2021). First Report of Resistance to Ivermectin in Parascaris univalens in Iceland. Journal of Parasitology. 107 , 16-22
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Abstract

Horses in Iceland have been isolated for more than 1,000 yr but still harbor a similar range of gastrointestinal parasites as do horses across the world. The long isolation of the horses and their parasites presumably means that no resistance genes have been introduced into the Parascaris spp. population. It is therefore of particular interest to investigate the efficacy of ivermectin on Parascaris spp. infecting Icelandic foals. Potential treatment failure of ivermectin in Iceland will add substantial new information on how resistance can arise independently. This study aimed to determine the efficacy of subcutaneous injection of ivermectin for the treatment of Parascaris spp. infection in foals and to identify the Parascaris species present in the west and north of Iceland. A fecal egg count reduction (FECR) test (FECRT) was performed on 50 foals from 8 farms, including an untreated control group of 6 foals, from September to November 2019. The foals were between 3 and 5 mo of age at the start of the study and had not previously been treated with anthelmintic drugs. Each foal was treated subcutaneously with off-label use of Ivomec (R) injection 10 mg/ml or Noromectin (R) 1% at a dose of 0.2 mg/kg. The FECR for each farm was calculated in 2 ways, by the eggCounts package in R and by the Presidente formula (FECRT). Both calculation methods resulted in efficacy levels between 0% and 80.78%, indicating ivermectin resistance on all farms. We also confirmed, by karyotyping, that the species of equine ascarid present in the west and north of Iceland is Parascaris univalens. This study provides evidence for treatment failure of ivermectin against P. univalens infection in foals. Since Icelandic horses have been isolated on the island for more than 1,000 yr, this implies that resistance alleles have developed independently in the Icelandic Parascaris population. The actual clinical impact of ivermectin resistance is unknown but another drug of choice should be considered to treat Parascaris infection in foals in Iceland.

Authors/Creators:Martin, Frida and Svansson, Vilhjalmur and Eydal, Matthias and Oddsdottir, Charlotta and Ernback, Maja and Persson, Isa and Tyden, Eva
Title:First Report of Resistance to Ivermectin in Parascaris univalens in Iceland
Series Name/Journal:Journal of Parasitology
Year of publishing :2021
Volume:107
Page range:16-22
Number of Pages:7
Publisher:ALLEN PRESS INC
ISSN:0022-3395
Language:English
Publication Type:Journal article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution-Noncommercial-No Derivative Works 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 403 Veterinary Science > Clinical Science
Keywords:Parascaris, Macrocyclic lactones, Ivermectin, Efficacy, Foals, Iceland, Equine, Fecal egg count reduction test
URN:NBN:urn:nbn:se:slu:epsilon-p-111226
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-111226
Additional ID:
Type of IDID
DOI10.1645/20-91
Web of Science (WoS)000613763200001
ID Code:22863
Faculty:VH - Faculty of Veterinary Medicine and Animal Science
Department:(VH) > Department of Biomedical Science and Veterinary Public Health
Deposited By: SLUpub Connector
Deposited On:31 Mar 2021 12:03
Metadata Last Modified:31 Mar 2021 12:11

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