Equine de-worming: a consensus on current best practice

Rendle, David; Austin, Corrine J.; Bowen, Mark; Cameron, I. R.; Furtado, Tamzin; Hodgkinson, Jane E.; McGorum, Bruce; Matthews, Jacqueline B.

doi:10.12968/ukve.2019.3.s.3

Cited by 31 publications

(39 citation statements)

References 35 publications

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“…In cyathostomins, anthelmintic resistance is widespread to both the benzimidazoles and pyrimidines ( Peregrine et al, 2014 ), often leaving the MLs as the only viable treatment option. This is reflected by current guidelines for equine parasite control, wherein it is recommended to primarily use MLs for strongyle control and only use other drug classes if pertinent testing has demonstrated good efficacy ( Nielsen et al, 2019 ; ESCCAP 2019 ; Rendle et al, 2019 ). While ML resistance has been remarkably slow to progress in cyathostomins, the data presented herein clearly demonstrate that a resistance break-through can happen, and likely is occurring elsewhere as well.…”

Section: Discussionmentioning

confidence: 99%

Importation of macrocyclic lactone resistant cyathostomins on a US thoroughbred farm

Nielsen

Banahan²,

Kaplan

2020

International Journal for Parasitology: Drugs and Drug Resistan

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Anthelmintic resistance in equine cyathostomins is both widespread and highly prevalent in the benzimidazole and tetrahydropyrimidine classes; however, reports of resistance to macrocyclic lactone (ML) drugs are sparse and sporadic. This study reports a case of clear ML resistance in a group of Thoroughbred yearlings imported from Ireland to the US in 2019. Fecal egg count reduction (FECR) following ivermectin administered in February 2020 demonstrated 100% reduction in the US bred yearlings, but 93.5%, 70.5%, and 74.5% reduction in three groups of the imported yearlings. The two former groups were then retreated with ivermectin, yielding FECRs of 33.8% and 23.5%, respectively. Horses from these two groups were then assigned randomly to two possible treatments; moxidectin or a triple combination of moxidectin, oxibendazole, and pyrantel pamoate. The groups treated with moxidectin had FECRs of 90.2%, 57.3%, and 50.0%, while the triple combination had a 100% FECR in all treated groups. Subsequently, the efficacy of ivermectin was reassessed in June 2020 yielding FECRs of 99.8%, 87.7%, and 62.0% in the three imported groups. The FECRs of the US bred yearlings all remained in the 99–100% range. This is the first study to clearly demonstrate ML resistance in cyathostomins and to confirm the suspicion through reassessment. These data demonstrate that ML-resistant cyathostomins were imported from Ireland and serve to illustrate that the global movement of horses has the potential to quickly spread ML-resistant parasite isolates around the world. The equine industry is strongly encouraged to routinely monitor anthelmintic efficacy, so occurrence of ML resistant cyathostomins can be detected and appropriate interventions implemented as early as possible.

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Section: Discussionmentioning

confidence: 99%

Importation of macrocyclic lactone resistant cyathostomins on a US thoroughbred farm

Nielsen

Banahan²,

Kaplan

2020

International Journal for Parasitology: Drugs and Drug Resistan

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“…Encouraging a fundamental change in focus/attitude by many horse owners and veterinarians would preferably be backed by evidence for no detrimental effects as a result of reduced/no treatments to older horses. For the past decades, key opinion leaders have recommended a reduction in anthelmintic treatment intensity through the use of surveillance-based approaches to slow further development of anthelmintic resistance (Gomez and Georgi, 1991; Duncan and Love, 1991; Kaplan and Nielsen, 2010; Tzelos and Matthews, 2016; Rendle et al, 2019). But, recent questionnaire surveys have illustrated that while horse owners may be willing to reduce overall treatment intensity (Robert et al, 2015; Nielsen et al, 2018), they are reluctant to incorporate FEC monitoring in a selective treatment approach unless mandated by prescription-only legislation (Nielsen et al, 2018; Becher et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

“…Different approaches include; extending the interval between treatments so that susceptible parasites can develop and pass eggs onto pasture between treatments, targeting treatments only to specific classes (mobs) of animals, allowing others to remain untreated, and ‘targeted selective treatments’ where specific animals within a mob remain untreated on the basis of some indicator of treatment need (Leathwick and Besier, 2014; Kenyon et al, 2009). In horses, surveillance-based treatments primarily based on FEC have been widely advocated (Gomez and Georgi, 1991; Duncan and Love, 1991; Kaplan and Nielsen, 2010; Tzelos and Matthews, 2016; Nielsen et al, 2019b, Nielsen et al, 2019a; Rendle et al, 2019) but uptake by owners appears limited (Nielsen et al, 2018; Becher et al, 2018). Effectively, in most situations, all horses continue to receive multiple anthelmintic treatments each year which questions the ability of horse owners to reduce selection of resistance to these important drugs.…”

Section: Introductionmentioning

confidence: 99%

Managing anthelmintic resistance in cyathostomin parasites: Investigating the benefits of refugia-based strategies

Leathwick

Sauermann

Nielsen

2019

International Journal for Parasitology: Drugs and Drug Resistan

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Selective anthelmintic therapy has been recommended as a sustainable strategy for cyathostomin control in horse populations for several decades. The traditional approach has been to determine strongyle fecal egg counts (FEC) for all horses, with treatment only recommended for those exceeding a predetermined threshold. The aims are to achieve a reduction of overall egg shedding, while leaving a proportion of the herd untreated, which lowers anthelmintic treatment intensity and reduces selection pressure for development of anthelmintic resistance. This study made use of the cyathostomin model to evaluate the influence of treatment strategies with between 1 and 8 yearly treatment occasions, where either 1) all horses were treated, 2) a predetermined proportion of the herd remained untreated, or 3) horses were treated if their FEC exceeded thresholds between 100 and 600 strongyle eggs per gram. Weather data representing four different climatic zones was used and three different herd age structures were compared; 1) all yearlings, 2) all mature horses 10–20 years old, and 3) a mixed age structure of 1–20 years of age. Results indicated a consistent effect of age structure, with anthelmintic resistance developing quickest in the yearling group and slowest among the mature horses. Development of anthelmintic resistance was affected by treatment intensity and selective therapy generally delayed resistance. Importantly, the results suggest that the effects of selective therapy on resistance development are likely to vary between climatic zones and herd age structures. Overall, a substantial delaying of resistance development requires that the average number of treatments administered annually across a herd of horses needs to be about two or less. However, results also indicate that an age-structured prioritisation of treatment to younger horses should still be effective. It appears that a ‘one-size-fits-all’ approach to the management of anthelmintic resistance in cyathostomins is unlikely to be optimal.

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“…However, it is questionable whether all potential factors were independent of each other. Indeed, climatic conditions affect the development of parasites on pasture, access to grazing areas may vary with season, owners may adapt the anthelminthic calendar to the age of their horses 30 . A simplified BN describing the relationship across the variables is given in Figure 4.…”

Section: Bayesian Networkmentioning

confidence: 99%

Study design synopsis: Battle in the stable: Bayesianism versus Frequentism

Detilleux¹

2020

Equine Veterinary Journal

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Frequentism dominates scientific practice although Bayesianism may provide an alternative, especially when analysing data from complex, high‐dimensional models. The key differences between Bayesianism and Frequentism are highlighted in the introduction. Next, I review the different stages of Bayesian statistical reasoning in a research setting, explain the key concepts and illustrate them with toy examples taken in equine veterinary medicine. An extension to more complex models (Bayes network) is introduced and guidelines are offered as a conclusion.

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Equine de-worming: a consensus on current best practice

Cited by 31 publications

References 35 publications

Importation of macrocyclic lactone resistant cyathostomins on a US thoroughbred farm

Importation of macrocyclic lactone resistant cyathostomins on a US thoroughbred farm

Managing anthelmintic resistance in cyathostomin parasites: Investigating the benefits of refugia-based strategies

Study design synopsis: Battle in the stable: Bayesianism versus Frequentism

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