Anthelmintic resistance of horse strongyle nematodes to ivermectin and pyrantel in Lithuania

Abstract

Background With intensive use of anthelmintic drugs in recent decades, anthelmintic resistance (AR) in horse nematodes is becoming a growing issue in many countries. However, there is little available information about the parasites, treatment practices or AR in the horse population in Lithuania. The aim of this study was to assess the current situation of AR on horse farms in Lithuania. The study was conducted in 25 stables on horses with a strongyle faecal egg count (FEC) of ≥ 200 eggs per gram. A faecal egg count reduction test (FECRT) was performed on each farm after administration of ivermectin (IVM) or pyrantel (PYR). Results The efficacy of IVM was comparatively high, with 98.8% of 250 horses having a zero egg count 14 days after treatment. Two conditions were used to interpret the FECRT results for PYR: firstly, resistance was determined when FECR was < 90% and the lower 95% confidence interval (LCL) was < 80%, and secondly when in addition the upper confidence level (UCL) was < 95%. Under the first condition, resistance against PYR was found in five stables (25% of all tested herds), while when considering the UCL as well, resistance was only detected in two stables (8%). The FEC showed a significant (P < 0.01) difference between the treatment and control groups. Only cyathostomin larvae were detected in larval cultures derived from strongyle-positive faecal samples collected 14 days after treatment of a test group with PYR. Conclusions This in vivo study showed that PYR resistance is prevalent on horse farms in Lithuania, while the efficacy of IVM still appears to be unaffected. However, further studies of ivermectin resistance are needed. These findings should guide the implementation of more sustainable management of strongyle infections in horses in Lithuania.

Anthelmintic resistance of horse strongyle nematodes to fenbendazole in Lithuania

“…Only CYA were detected in larval cultures derived from strongyle-positive faecal samples collected 14 days after treatment with FBZ. Recent surveys show a decreasing prevalence of large strongyles in horse stables worldwide [7,[35][36][37][38], including Lithuania [19], while CYA are now considered the most important group of horse parasites [39,40]. The prevalence of resistance to FBZ in Lithuanian horses detected in this study is similar to that recently described in other European countries such as Norway [41], Denmark [42] and the UK [43].…”

“…Four anthelmintics belonging to three classes based on their chemical structure and pharmacological behaviour Dauparaitė et al Acta Veterinaria Scandinavica (2022) 64:26 are used for controlling strongylid infections in Lithuania: Fenbendazol (FBZ), a benzimidazole (BZ); PYR, a tetrahydropyrimidine, and two MLs: ivermectin (IVM) and moxidectin (MOX). A nationwide study was performed in Lithuania in 2021 that evaluated IVM and PYR anthelmintics registered for the control of strongylid infections, and reported resistance to PYR and sufficient IVM efficacy [19]. However there are only limited data on the resistance of strongylids to FBZ drugs.…”

Comparison of FECPAKG2, a modified Mini-FLOTAC technique and combined sedimentation and flotation for the coproscopic examination of helminth eggs in horses

“…Due to the widespread anthelmintic resistance in cyathostomins and Parascaris spp. [ 5 , 11 , 19 , 23 – 26 ], this can be expected to lead to continued egg shedding and contamination of the environment with eggs produced by resistant worms.…”

Identifying 3rd larval stages of common strongylid and non-strongylid nematodes (class: Nematoda) infecting Egyptian equines based on morphometric analysis

“…For instance; anorexia, reduced feed intake, and diarrhea [ 3 , 4 ] elicit a diminished weight gain and degradation of traction power. Gastrointestinal nematodes infecting equines include; (A) strongylid nematodes, which make up about 75% of the total parasite population infecting equines [ 5 , 6 ], and (B) Non-strongylid nematodes which include Parascaris equorum , Habronema spp., Draschia megastoma , Oxyuris equi , Trichostrongylus axei and Strongyloides westeri [ 5 ].…”