Reduction of the nematode egg reappearance period in horses after anthelmintic therapy

Abstract

Background and Aim: Anthelmintics are used to control equine nematodes. However, helminth resistance to regularly used drugs is a well-known challenge. Among tests to assess effective control and monitor resistance, the most common is the fecal egg count reduction test (FECRT). In the absence of reliable FECRT results, the nematode egg reappearance period (ERP) is taken into account. This study aimed to examine horses from farms around the Moscow Region to assess nematode resistance through ERP after therapy. Materials and Methods: In the first stage, fecal samples from 280 horses were examined by the flotation method with a sodium nitrate solution. The eggs per gram (EPG) in feces were counted using the modified McMaster technique. One hundred and forty out of 280 horses were selected for further work. Five groups were formed: Two groups of horses infected with strongyles (n = 50) and three groups with Parascaris equorum (n = 90). Therapy against strongyles was performed with albendazole and ivermectin. Therapy for parascaridosis was performed with fenbendazole, ivermectin, and aversectin C. Samples from the horses in each group were taken on the 14th day (2 weeks), 28th day (4 weeks), 42nd day (6 weeks), 56th day (8 weeks), and 84th day (12 weeks) after treatment, and the amount of EPG in each sample was determined. Results: Overall, nematodes were found in 65% of the horses examined. P. equorum was most frequently recorded (42.1%) followed by Strongylidae gen. spp. (27.9%). The strongyles ERP after therapy with albendazole and ivermectin was estimated on 42 days (6 weeks). The growth of P. equorum eggs in the feces was observed from the 56th day (8 weeks) after therapy with fenbendazole, from the 42nd day (6 weeks) after therapy with ivermectin, and was observed from the 84th day (12 weeks) after the use of aversectin. Conclusion: Our study shows widespread reductions in nematode ERPs across the Moscow Region after ivermectin therapy in horses, suggesting that additional monitoring of these farms is needed for effective control of anthelmintic resistance.

Prevalence of intestinal nematodes in equines with an assessment of the therapy using Albendazole and Doramectin

“…[15] In this study, the overall prevalence of parasitic nematodes among examined equines was 70.25%. These ndings are nearly similar to the prevalence recorded by Baranova et al (2022) at 65%, [16] and lower than that investigated by Debere et al (2018) at 88.8%, [14] and Mathewos et al (2021;2022) at 78.5% and 94.5%, respectively. [17,18] Regarding the analysis of variables potentially associated with an increased risk of infection, the prevalence of intestinal helminths in donkeys is estimated to be higher (80%) than in working horses (56.25%).…”

Preliminary screening of plant essential oils from an oceanic climate zone (NW Spain) for the control of equine cyathostomins

“…The study of plant extracts and phytotherapy has increased due to the reduced efficacy of some commercial anthelmintics to control GIN, which may evolve into anthelmintic resistance (AR) in part due to the overuse of these drugs to maintain animal productivity [2,3,27]. Besides this, the search for secondary metabolites derived from essential oils is important in equine nematodes because they promote one health considering that these species share some pathogens, niche adaptation, epidemiology, vector transmission, culture resources, food safety and biosecurity with humans [14].…”

“…Most known genera include the small strongyles or cyathostomins (Trichonema, Cyalocephalus, Cyathostomum and Gyalocephalus) and large strongyles (Strongylus and Triodontophorus), which are responsible for mild to severe clinical injury [16,17]. Control of these nematodes involves commercial anthelmintic drugs which are administered to reduce the impact of parasites on animal health and improve their productivity [2]. However, the overuse of different drugs has been pointed as a cause of anthelmintic resistance (AR) identified in the main GIN species, causing low effectiveness [27], thus sustainable control alternatives have been required [31].…”

Patterns of Equine Small Strongyle Species Infection after Ivermectin Intervention in Thailand: Egg Reappearance Period and Nemabiome Metabarcoding Approach

“…Previous reports have shown that the ERP in IVM-treatment is typically 8-13 weeks [35][36][37]. However, recent studies have indicated a reduced ERP 6-8 weeks after treatment [38,39]. The rationale behind this phenomenon may be attributed to an increased selection pressure for resistance development in specific species or a potential reduction in the efficacy of anthelmintics against the luminal stages of cyathostomins [32].…”