Anthelmintic Resistance in Equine Nematodes – A Review on the Current Situation, with Emphasis in Europe

Abstract

Since the introduction of the last equine broad-spectrum anthelmintic group in the 1980’s, the investment in new drugs to control horse’s parasites did not result in new advancements. These drugs allowed a very effective and extensive control of equine nematodes through successful interval dosing programs, firstly introduced in the 1960’s. However, the widespread and indiscriminate use of anthelmintics in these intensive treatments have led to increasing resistance in the major equine nematodes. Reports of reduced effectiveness are virtually worldwide and repercussions in livestock production farms have already been seen.Based on recent questionnaires about horse farm practices, preventive measures and international recommendations, it is clear that most of them are still not being widely implemented. It is also clear that these recommendations are outdated and new approaches must be considered to correctly tackle this rapidly evolving issue in horse management, as more accurate diagnostic methods are currently available, such as Mini-FLOTAC. This article intends to do a general review of the history and current situation of anthelmintic resistance in horses, with emphasis in Europe, as well as, how to diagnose and delay or even prevent its further development, mentioning new methods of diagnostic and directions in which to develop research.

Evaluation of Fecal Egg Count Tests for Effective Control of Equine Intestinal Strongyles

“…Mini-FLOTAC had a comparatively better CV% (average < 28.3) and bead recovery average of >65% among the three methods. Our result corroborated the findings of other studies that confirmed less variance for Mini-FLOTAC [28][29][30]. The modified McMaster had a CV% of >40 for all variants except ZnSO 4 and improved recovery of >90% for all variants except NaNO 3 .…”

“…For the modified McMaster method, most replicates tended to disperse away from the slope. However, many replicates overestimated spiked beads, indicating a potential threat of false counts [29]. The modified Wisconsin method variants performed better in counting the lower bead standards whereas the higher ones tended to disperse away from the slope.…”

“…The modified McMaster had a CV% of >40 for all variants except ZnSO 4 and improved recovery of >90% for all variants except NaNO 3 . The superiority of the modified McMaster technique in the apparent recovery of a higher number of beads is attributed to its bigger multiplication factor [29]. All variants of modified Wisconsin except sugar 1.33 had CV% > 32 and average recovery as low as 44.6%.…”

Anthelmintic resistance in equine nematodes: Current status and emerging trends

“…The status of anthelmintic resistance in equine nematodes has been reviewed multiple times over the past couple of decades ( Kaplan, 2002 , 2004 ; von Samson-Himmelstjerna, 2012 ; Matthews, 2014 ; Peregrine et al, 2014 ; Silva et al, 2019 ). However, several new developments reported in the past decade prompts a new review.…”

Inclusion of Sainfoin in the Diet Might Alter Strongyle Infection in Naturally Infected Horses

“…This has inevitably selected for anthelminthic resistance, and, not surprisingly, resistance to drugs is now commonly observed, especially in cyathostomins [3]. Controlling these strongyles with the currently used molecules is therefore more difficult [4]. In addition, although treating equine infections is necessary for animal health, the use of anthelmintic drugs has been associated with an increased risk of developing colic in the week following an anthelminthic treatment [5].…”