A review of the use of moxidectin in horses

Abstract

Summary Moxidectin has broad‐spectrum anti‐nematodal and anti‐arthropodal activities in the horse but is not effective against tapeworms or flukes. Moxidectin and ivermectin have the same efficacy against internal, adult parasites of horses. Moxidectin, however, is highly effective in eliminating encysted and hypobiotic larval stages of cyathostomins, whereas ivermectin is not. Treatment of horses with moxidectin results in an egg‐reappearance period (ERP) of 15–24 weeks. Because of its long ERP, moxidectin is labelled to be used at 12 week intervals. Moxidectin may provide protection against infection by ingested cyathostomin larvae for 2–3 weeks after it is administered. The larvicidal activity of moxidectin has often been compared to that of fenbendazole administered at either 7.5 or 10 mg/kg bwt for 5 consecutive days. The efficacy of fenbendazole, when administered daily for 5 consecutive days at 7.5 or 10 mg/kg bwt, against all stages of cyathostomins is often less than that of moxidectin because resistance of cyathostomins to benzimidazoles is prevalent worldwide, and the 5 day course of fenbendazole does not overcome this resistance. There are now reports of resistance of ascarids to moxidectin. Overt resistance of cyathostomins and a shortened egg re‐emergence period after treatment with moxidectin have been reported. Rapid removal of manure by natural fauna can significantly reduce larval nematode concentrations and thereby reduce intervals of anthelmintic treatment. Of the macrocyclic lactones, moxidectin has the least deleterious effect on faecal fauna.

Effects of food substrates and moxidectin on development of black soldier fly, Hermetia illucens

“…Moxidectin was toxic to developing black soldier fly larvae. This contradicts its general reputation of being relatively benign to coprophagous insects (Floate et al., ; Schumacher & Taintor, ). However, our finding is not really surprising, given moxidectin is an insecticide with a known activity against bot flies (Diptera: Oestridae).…”

“…A large proportion of administered endectocides ends up excreted with faeces, potentially affecting their suitability to saprophagous arthropods (Floate, Wardhaugh, Boxall, & Sherratt, 2005). Among the commonly used active ingredients, moxidectin is considered to be the least toxic to non-target organisms (Floate et al, 2005;Schumacher & Taintor, 2008). However, it is not completely harmless, with at least some deleterious effects reported for fly larvae (Doherty, Sewart, Cobb, & Keiran, 1994;Suárez, Lifschitz, Sallovitz, & Lanusse, 2009).…”

Anthelmintic resistance in equine helminth parasites – a growing issue for horse owners and veterinarians in New Zealand?

“…The use of persistent drugs has been seen as a factor in the development of resistance in the nematodes of ruminants (Sutherland et al 1997) and this may also be important in horses (Sangster 1999;Schumacher and Taintor 2008). Moxidectin is detectable in the plasma of treated horses for at least 75 days (Perez et al 1999).…”

“…For moxidectin this period has been shown to be somewhat variable against presumably fully susceptible worms, but is generally longer than that for ivermectin; 15-24 weeks for moxidectin as opposed to 8-14 weeks for ivermectin (Schumacher and Taintor 2008;Molento et al 2012). …”

A review on the treatment and control of ectoparasite infestations in equids

“…Avermectins appear to control lice and mites on horses, as they are effective against lice and mites when given parenterally to cattle (Schumacher & Taintor, 2008 More effective when environment also treated (Littlewood et al, 1995;Osman et al, 2006) Moxidectin Oral…”