Field tests demonstrating reduced activity of ivermectin and moxidectin against small strongyles in horses on 14 farms in Central Kentucky in 2007–2009

• Published in: Parasitology research (1987) 2011-02, Vol.108 (2), p.355-360
• Main Authors: Lyons, Eugene T., Tolliver, Sharon C., Collins, Sandra S., Ionita, Mariana, Kuzmina, Tetiana A., Rossano, Mary
• Format: Article
• Language: English
• Subjects: Analysis; Animals; Anthelmintics - therapeutic use; Anti-infective agents; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Female; Fundamental and applied biological sciences. Psychology; General aspects; General aspects and techniques. Study of several systematic groups. Models; Horse Diseases - drug therapy; Horse Diseases - epidemiology; Horse Diseases - parasitology; Horses; Immunity, Innate; Immunology; Invertebrates; Ivermectin - therapeutic use; Kentucky - epidemiology; Macrolides - therapeutic use; Medical Microbiology; Microbiology; Original Paper; Pharmacology, Experimental; Research Report; Strongyle Infections, Equine - drug therapy; Strongyle Infections, Equine - epidemiology; Strongyle Infections, Equine - parasitology; Strongylus - drug effects; Strongylus - isolation & purification; Strongylus - physiology; Testing; Treatment Outcome
• ISSN: 0932-0113; 1432-1955
• DOI: 10.1007/s00436-010-2068-7

Efficacy of ivermectin (IVM) and moxidectin (MOX) against small strongyles was evaluated in horses ( n  = 363) in field tests on 14 farms in Central Kentucky between 2007 and 2009. Most of the horses were yearlings but a few were weanlings and mares. The number of horses treated with IVM was 255 and those treated with MOX was 108. Horses on six farms were allotted into two groups. One group was treated with each of the two drugs, whereas horses on the other eight farms were treated with only one of the two drugs—IVM on six farms and MOX on two farms. Strongyle eggs per gram of feces (EPGs) compared to initial use of IVM and MOX returned almost twice as quickly after treatment of horses on all of the farms. IVM has been used much more extensively in this geographical area than MOX. Reduced activity of MOX was evident even on farms with rare or no apparent previous use of MOX but with probable extensive use of IVM.