title: Decreased strongyle egg re-appearance period after treatment with ivermectin and moxidectin in horses in Belgium, Italy and The Netherlands.
abstract: The objective of the present study was to evaluate the efficacy of an oral treatment with ivermectin (IVM) or moxidectin (MOX) against gastro-intestinal strongyles in naturally infected horses by performing a faecal egg count reduction test (FECRT) and by monitoring the egg reappearance period (ERP) after treatment. Therefore, a field efficacy study with a randomised complete block design for each study site was conducted, with the individual animal as the experimental unit. At least 10 study sites in Italy, Belgium and The Netherlands were selected and animals were allocated to one of the two treatment groups based on the pre-treatment faecal egg counts (FEC). Animals were treated on Day 0 with an oral paste containing either IVM (at 0.2mg/kg bodyweight) or MOX (at 0.4 mg/kg bodyweight). After treatment, faecal samples were collected at least every fortnight during 56 days after treatment with IVM and during 84 days after MOX treatment. In total, 320 horses on 32 farms were examined. The FECRT on Day 14 indicated a 100% efficacy in 59 of the 64 treatment groups and >92% efficacy in the remaining 5 groups. The ERP was decreased for at least one of the anthelmintics on 17 out of 32 study sites (15 sites or 47% for MOX and 17 sites or 53% for IVM) and on 9 sites (28%) the ERP was decreased for both anthelmintics. On some of these study sites the efficacy declined at the end of the expected ERP, often with good efficacy 2 weeks earlier. Nevertheless, on 1, 3 and 5 study sites in Italy, Belgium and The Netherlands respectively, an efficacy below 90% for IVM and MOX was identified as soon as Day 42 or Day 56. In The Netherlands, the efficacy of IVM was below 90% from Day 28 or Day 35 after treatment on 1 site each. The present study reports a high efficacy of MOX and IVM in a FECRT 14 days after treatment, yet does indicate a shortened ERP for these treatments in more than half of the selected study sites.
authors.affiliation: Zoetis, Mercuriuslaan 20, 1930 Zaventem, Belgium. Electronic address: thomasgeurden@yahoo.com.
authors.forename: Thomas
authors.initials: T
authors.lastname: Geurden
authors.affiliation: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL Utrecht, The Netherlands.
authors.forename: Deborah
authors.initials: D
authors.lastname: van Doorn
authors.affiliation: Laboratory for Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Edwin
authors.initials: E
authors.lastname: Claerebout
authors.affiliation: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL Utrecht, The Netherlands.
authors.forename: Frans
authors.initials: F
authors.lastname: Kooyman
authors.affiliation: Zoetis, Mercuriuslaan 20, 1930 Zaventem, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: De Keersmaecker
authors.affiliation: Laboratory for Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Jozef
authors.initials: J
authors.lastname: Vercruysse
authors.affiliation: Zoetis, Mercuriuslaan 20, 1930 Zaventem, Belgium.
authors.forename: Bruno
authors.initials: B
authors.lastname: Besognet
authors.affiliation: Zoetis, Mercuriuslaan 20, 1930 Zaventem, Belgium.
authors.forename: Bindu
authors.initials: B
authors.lastname: Vanimisetti
authors.affiliation: Department of Animal Medicine, Production and Health, University of Padova, Viale dell'Università 16, 35020 Legnaro, PD, Italy.
authors.forename: Antonio Frangipane
authors.initials: AF
authors.lastname: di Regalbono
authors.affiliation: Faculty of Veterinary Medicine, University of Udine, Via delle Scienze 206, 33100 Udine, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Beraldo
authors.affiliation: Faculty of Veterinary Medicine, University of Teramo, Piazza A. Moro 45, 64100 Teramo, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Di Cesare
authors.affiliation: Faculty of Veterinary Medicine, University of Teramo, Piazza A. Moro 45, 64100 Teramo, Italy.
authors.forename: Donato
authors.initials: D
authors.lastname: Traversa
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D001530:Belgium / Q000453:epidemiology; D005243:Feces / Q000469:parasitology; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy / Q000453:epidemiology*; D006736:Horses; D007558:Italy / Q000453:epidemiology; D007559:Ivermectin / Q000627:therapeutic use*; D018942:Macrolides / Q000627:therapeutic use*; D009426:Netherlands / Q000453:epidemiology; D010270:Parasite Egg Count / Q000662:veterinary; D013319:Strongyle Infections, Equine / Q000188:drug therapy / Q000453:epidemiology*
chemical_list: D000871:Anthelmintics; D018942:Macrolides; D007559:Ivermectin; C027837:moxidectin
keywords: Cyathostominae; Efficacy; Egg reappearance period; Horse; Ivermectin; Moxidectin