Efficacy of selected anthelmintic drugs against cyathostomins in horses in the federal state of Brandenburg, Germany.
Cyathostomins are currently the most common internal parasites of horses. With the intensive use of anthelmintic drugs over the past decades, resistance of cyathostomins to anthelmintics is becoming a growing problem in many countries. The aim of this study was to assess the current situation on horse farms in the German federal state of Brandenburg. A pre-selected population of horses from 24 premises that had shown a prevalence of cyathostomins higher than the average in a previous study was examined for anthelmintic efficacy. Faecal egg count reduction tests (FECRTs) were performed for ivermectin (IVM) and pyrantel (PYR). For IVM, the egg reappearance period (ERP) was also examined, as a shortened ERP can be indicative of developing resistance. The efficacy of IVM on cyathostomins was high: 99.1 % of 224 horses had a zero egg count 14 days after treatment. No shortening of the ERP was detected. For the data of the FECRT for PYR, three different methods of calculation were employed: (a) the method as recommended by the World Association for the Advancement of Veterinary Parasitology (WAAVP), (b) a bootstrapping method and (c) a Markov chain Monte Carlo method. Two methods of interpretation for these data were used: Resistance was declared (a) when FECR was <90 % and the lower 95 % confidence interval (LCL) <80 % and (b) when additionally the upper 95 % confidence level (UCL) was <95 %. When applying the first interpretation, resistance against PYR was found on four yards, while, when considering the UCL, all three methods for calculation only detected resistance on one single yard. Twelve species of cyathostomins were detected in larval cultures derived from strongyle egg positive faecal samples collected 14 days after treatment with PYR by reverse line blot hybridization (RLB). In order to generate comparable data, it is suggested to establish international standards for the calculation of FECRT data.
Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Robert-von-Ostertag-Street. 7-13, D-14163, Berlin, Germany. juliane.fischer@uba.de.
Juliane K
JK
Fischer
Institute of Parasitology, University of Veterinary Medicine, Veterinärplatz 1, 1210, Vienna, Austria. barbara.hinney@vetmeduni.ac.at.
Barbara
B
Hinney
Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 1870, Frederiksberg C, Denmark. md@sund.ku.dk.
Matthew J
MJ
Denwood
Faculty of Veterinary Medicine, Teramo, Italy. dtraversa@unite.it.
Donato
D
Traversa
Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Robert-von-Ostertag-Street. 7-13, D-14163, Berlin, Germany. gvsamson@fu-berlin.de.
Georg
G
von Samson-Himmelstjerna
Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Robert-von-Ostertag-Street. 7-13, D-14163, Berlin, Germany. peter-henning.clausen@fu-berlin.de.
Peter-Henning
PH
Clausen
D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage*; D004351:Drug Resistance; D005243:Feces / Q000469:parasitology; D005858:Germany; D006734:Horse Diseases / Q000188:drug therapy* / Q000469:parasitology; D006736:Horses; D007559:Ivermectin / Q000008:administration & dosage; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D010270:Parasite Egg Count / Q000662:veterinary; D017183:Strongylida / Q000187:drug effects* / Q000502:physiology; D017206:Strongylida Infections / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D016896:Treatment Outcome
D000871:Anthelmintics; D007559:Ivermectin
Anthelmintics; Cyathostomins; Horses; Nematodes; Resistance