Comparative studies of ivermectin and moxidectin in the control of naturally acquired cyathostome infections in horses

Abstract

The control of naturally acquired cyathostome infections in horses by treatments with ivermectin and moxidectin was evaluated in three field studies. In a first study the efficacy of both drugs was assessed in a faecal egg count reduction test. Both ivermectin and moxidectin demonstrated efficacies greater than 99 per cent for up to 60 days after treatment. In a second study, the period required for strongyle eggs to reappear was estimated in horses treated either with ivermectin or moxidectin. For the horses treated with ivermectin the period varied between 10 and approximately 13 weeks, and for moxidectin between 22 and approximately 24 weeks. With both drugs strongyle eggs started to reappear in the faeces significantly earlier in foals and young horses than in adults. In a third study, two prophylactic dosing schemes involving three ivermectin treatments at intervals of eight weeks, and two moxidectin treatments 12 weeks apart, were found to be highly effective in controlling strongyle infections of horses on pasture.

A comparison of the efficacy and pharmacokinetics of ivermectin after spring and autumn treatments against Cyathostominae in horses

“…Nematodes were excreted in the periods similar to those observed by other authors (Demeulenaere et al 1997, Abbot et al 2003, Osterman Lind et al 2003, Steinbach et al 2006. No significant differences were observed in the egg reappearance period (ERP) which was estimated at 9-10 weeks in both seasons, and the above is even longer compared with the findings of other authors (Bello 1996, Demeulenaere et al 1997, Reinemeyer and Clymer 2002. Demeulenaere et al (1997) suggested that the egg reappearance period should be redefined as "the period after antihelmintic treatment during which no eggs or small but acceptable numbers of eggs are excreted".…”

“…Despite differences in serum drug concentrations between spring and autumn treatments, a comparable clinical effect was achieved. Nematodes were excreted in the periods similar to those observed by other authors (Demeulenaere et al 1997, Abbot et al 2003, Osterman Lind et al 2003, Steinbach et al 2006. No significant differences were observed in the egg reappearance period (ERP) which was estimated at 9-10 weeks in both seasons, and the above is even longer compared with the findings of other authors (Bello 1996, Demeulenaere et al 1997, Reinemeyer and Clymer 2002.…”

“…No significant differences were observed in the egg reappearance period (ERP) which was estimated at 9-10 weeks in both seasons, and the above is even longer compared with the findings of other authors (Bello 1996, Demeulenaere et al 1997, Reinemeyer and Clymer 2002. Demeulenaere et al (1997) suggested that the egg reappearance period should be redefined as "the period after antihelmintic treatment during which no eggs or small but acceptable numbers of eggs are excreted". The proposed definition of ERP supports longer intervals between consecutive dewormings, in particular in winter months when horses receive dry feed and are less likely to ingest invasive larvae of small strongylids.…”

“…Some programs offer treatment to all horses which use the same pasture at the same time, regardless of the severity of the parasitic infection, in spring (before the pasture season) and in autumn (after the pasture season) Henton 1987, Lyons et al 1999) In a different treatment scheme, antiparasitic drugs are administered more frequently, every 8-10 weeks or even daily (Drudge and Lyons 1989, Bello 1996, Reinemeyer and Clymer 2002. According to many researchers (Demeulenaere et al 1997, Lyons et al 1999, Gawor and Kita 2006 to prevent the development of drug resistance, antiparasitic drugs should be administered only to horses in whose feces the number of excreted eggs exceeds the "safe" margin (40-200 per 1 gram of feces).…”

Selected blood immunological and biochemical parameters in horses infected with Cyathostominae before and after ivermectin treatment

“…According to published data (2,4,18), the egg reappearance period (ERP) after ivermectin treatment lasts from 8 to 12 weeks. The results of our study corroborate the above findings.…”