Egg reappearance periods of anthelmintics against equine cyathostomins: The state of play revisited

Macdonald, Stephanie L; Abbas, Ghazanfar; Ghafar, Abdul; Gauci, Charles G.; Bauquier, Jenni; El-Hage, Charles; Tennent‐Brown, Brett; Wilkes, Edwina; Beasley, Anne; Jacobson, Caroline; Cudmore, Lucy; Carrigan, Peter; Hurley, John; Beveridge, Ian; Hughes, Kristopher; Nielsen, Martin K.; Jabbar, Abdul

doi:10.1016/j.ijpddr.2022.12.002

Cited by 18 publications

(12 citation statements)

References 88 publications

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“…The adoption of other approaches for parasite control, such as husbandry and farm management, has been low among horse farm managers and owners ( O'Meara and Mulcahy, 2002 ; Saeed et al, 2019 ; Wilkes et al, 2020 ). The frequent and indiscriminate use of anthelmintics has resulted in the development of anthelmintic resistance (AR) in ascarids and cyathostomins against the commonly used anthelmintics, including benzimidazoles (BZs), tetrahydropyrimidines (THPs) and macrocyclic lactones (MLs) ( Nielsen, 2022 ; Macdonald et al, 2023 ). The patterns for the development of AR in ascarids and cyathostomins are of importance, as there is widespread resistance to MLs in Parascaris spp.…”

Section: Introductionmentioning

confidence: 99%

A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses

Abbas,

Ghafar,

McConnell

et al. 2024

International Journal for Parasitology: Drugs and Drug Resistan

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Section: Introductionmentioning

confidence: 99%

A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses

Abbas,

Ghafar,

McConnell

et al. 2024

International Journal for Parasitology: Drugs and Drug Resistan

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“…Identification of a reduction of the ERP following anthelmintic treatment has been considered as an early indicator of emerging anthelmintic resistance (Sangster, 1999). However, it is unclear whether the observed reducing ERP profiles of macrocyclic lactone anthelmintics are due solely to the acquisition of anthelmintic resistance, or to other factors related to individual horses, cyathostomin species, and/or the environmental conditions (Nielsen et al 2022;Macdonald et al 2023). There have been a limited number of previous studies of the ERP following moxidectin treatment performed in the UK horse population.…”

Section: Discussionmentioning

confidence: 99%

Strongyle Egg Reappearance Periods following Moxidectin Treatment in Horses in Southeast England

Mair

Opie

Moreton-Clack

et al. 2023

Preprint

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Background: A reduction in the Egg Reappearance Period (ERP) has been suggested to be an early indication of emerging anthelmintic resistance in strongyles. Objective:To measure the strongyle ERP following moxidectin treatment of horses in the southeast of England. Study Design: Prospective study. Methods: Horses with a faecal egg count (FEC) of > 400 strongyle eggs per gram (EPG) in a routine screening sample were enrolled into the study. Moxidectin (400 mcg/kg) was administered per os and FEC tests repeated every 2 weeks for 16 weeks. Results: Forty-eight horses completed the study. The mean EPG prior to treatment was 1047 (range 375 – 2137 EPG). In all but two horses, FEC was 0 EPG 2 weeks after moxidectin administration. In the remaining two, the FECs were 12.5 EPG (97.8-98.3% reductions compared to pre-treatment FEC). At 4 weeks post-treatment, 6 horses had positive FECs (96.6-99.2% reductions). At 6 weeks, 11 horses had positive FECs (83.8% reduction in one horse; >90% reduction in 10). At 8 weeks, 21 horses exhibited positive FECs (<90% reduction in 2). At 10 weeks, 27 horses had positive FECs (<90% in 6). At 12 weeks, 31 horses had positive FECs (<90% reduction in 11). At 14 weeks, 34 horses had positive FECs (<90% reduction in 13). At 16 weeks, 38 horses had positive FECs (<90% reduction in 17). Limitations: Weights of some horses were estimated using weigh tapes rather than a weighbridge. Dosing of the horses with moxidectin was carried out by owners. Conclusions: The results indicated acceptable efficacy of moxidectin at 14 days after treatment; however, the ERP pattern measured across the group suggest that this anthelmintic has a considerably shorter suppressive effect on strongyle egg shedding than measured when it was first introduced ( >13 weeks and up to 24 weeks).

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“…It is unclear whether the observed reducing ERP profiles of macrocyclic lactone anthelmintics are due solely to the acquisition of anthelmintic resistance, or to other factors related to individual horses, cyathostomin species, re‐population of the intestines with fourth‐stage larvae following treatment, and/or the environmental conditions (Macdonald et al, 2023; Nielsen, Littman, et al, 2022; Nielsen, von Samson‐Himmelstjerna, et al, 2022; Nielsen, Steuer, et al, 2022). There have been a limited number of previous studies of the ERP following moxidectin treatment performed in the UK horse population.…”

Section: Discussionmentioning

confidence: 99%

“…The determination of ERP following anthelmintic treatment has been suggested as a useful indicator for the early development of anthelmintic resistance in cyathostomins (Sangster, 1999). A number of studies have been published that assessed ERP following moxidectin treatment (reviewed by Macdonald et al, 2023) and, in the past decade, several of these have reported reduced ERP following treatment with moxidectin in the UK (Daniels & Proudman, 2016; Relf et al, 2014; Tzelos et al, 2017), suggesting that resistance to this compound is emerging. In view of the widespread routine use of moxidectin in competition and pleasure horses across all regions of the UK, information about how effective moxidectin is against cyathostomin populations in different regions of the country will be valuable in order to inform local recommendations for parasite control.…”

Section: Introductionmentioning

confidence: 99%

Strongyle egg reappearance periods following moxidectin treatment in horses in Southeast England

Mair

Opie

Moreton-Clack

et al. 2023

Equine Veterinary Education

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BackgroundA reduction in the egg reappearance period (ERP) has been suggested to be an early indication of emerging anthelmintic resistance in strongyles.ObjectiveTo measure the strongyle ERP following moxidectin treatment of horses in the southeast of England.Study designProspective study.MethodsHorses with a faecal egg count (FEC) of ≥400 strongyle eggs per gram (EPG) in a routine screening sample were enrolled into the study. Moxidectin (400 μg/kg) was administered per os and FEC tests repeated every 2 weeks for 16 weeks.ResultsForty‐eight horses completed the study. The mean EPG prior to treatment was 1047 (range 375–2137 EPG). In all but two horses, FEC was 0 EPG 2 weeks after moxidectin administration. In the remaining two, the FECs were each 12.5 EPG (97.8%–98.3% reductions compared to pre‐treatment FEC). At 4 weeks post‐treatment, 6 horses had positive FECs (96.6%–99.2% reductions). At 6 weeks, 11 horses had positive FECs (83.8% reduction in one horse; >90% reduction in 10). At 8 weeks, 21 horses exhibited positive FECs (<90% reduction in 2). At 10 weeks, 27 horses had positive FECs (<90% in 6). At 12 weeks, 31 horses had positive FECs (<90% reduction in 11). At 14 weeks, 34 horses had positive FECs (<90% reduction in 13). At 16 weeks, 38 horses had positive FECs (<90% reduction in 17).Main limitationsWeights of some horses were estimated using weigh tapes rather than a weighbridge. Dosing of the horses with moxidectin was carried out by owners.ConclusionsThe results indicated acceptable efficacy of moxidectin at 14 days after treatment; however, the ERP pattern measured across the group suggests that this anthelmintic has a considerably shorter suppressive effect on strongyle egg shedding than measured when it was first introduced (12–16 weeks).

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Egg reappearance periods of anthelmintics against equine cyathostomins: The state of play revisited

Cited by 18 publications

References 88 publications

A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses

A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses

Strongyle Egg Reappearance Periods following Moxidectin Treatment in Horses in Southeast England

Strongyle egg reappearance periods following moxidectin treatment in horses in Southeast England

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