title: Prevalence of anthelmintic resistance on Lithuanian sheep farms assessed by in vitro methods.
abstract: BACKGROUND
  This study examines the prevalence of drug resistance in gastrointestinal nematodes to macrocyclic lactones (ML) and benzimidazoles (BZ) in Lithuanian sheep using sensitive and precise in vitro methods. The survey was conducted from August 2013 to November 2014. Thirty-three farms with sheep previously treated with BZ and ivermectin (IVM) were included in the study. On 12 farms where only BZ were used, egg hatch discrimination dose testing (EHDDT) was conducted to detect anthelmintic resistance (AR) to BZ. On eight farms where only ML were used, micro agar larval development testing (MALDT) was conducted to detect AR to ivermectin (IVM). On the remaining 13 farms, where both classes of drugs were used, EHDDT and MALDT were both applied to detect multidrug resistance to BZ and IVM.
  
  
  RESULTS
  BZ-resistant gastrointestinal nematodes were found on all 25 farms with a previous history of BZ use. High levels of resistance (>40 % of hatching) were recorded on 36 % of these farms, and low levels (<20 % of hatching) on 40 % of farms. IVM-resistant populations were found on 13 out of 21 sheep farms using this drug. Of these 13 farms with AR to IVM, low levels of resistance (<30 % development) were recorded on 84.6 % of farms and high levels (>30 % development) on 15.4 % of farms. No resistance to IVM was recorded on 38.1 % of farms. Multi-drug resistance was detected on five farms out of 13 (38.5 %) using both classes of drugs.
  
  
  CONCLUSIONS
  The present study demonstrates the existence of AR to BZ and ML on Lithuanian sheep farms thus confirming results in a previous in vivo study. Cases of multi-drug resistance were recorded in the present study and require further consideration. An appropriate strategy for anthelmintic treatment, measures to prevent gastrointestinal nematode infection and a better understanding of the management practices associated with resistance may slow down further development of AR.
authors.affiliation: Department of Infectious Diseases, Veterinary Academy, Lithuanian University of Health Sciences, Tilžės 18, LT-47181, Kaunas, Lithuania. tomas.kupcinskas@lsmuni.lt.
authors.forename: Tomas
authors.initials: T
authors.lastname: Kupčinskas
authors.affiliation: Department of Infectious Diseases, Veterinary Academy, Lithuanian University of Health Sciences, Tilžės 18, LT-47181, Kaunas, Lithuania. inga.stadaliene@lsmuni.lt.
authors.forename: Inga
authors.initials: I
authors.lastname: Stadalienė
authors.affiliation: Department of Infectious Diseases, Veterinary Academy, Lithuanian University of Health Sciences, Tilžės 18, LT-47181, Kaunas, Lithuania. mindaugas.sarkunas@lsmuni.lt.
authors.forename: Mindaugas
authors.initials: M
authors.lastname: Šarkūnas
authors.affiliation: Department of Infectious Diseases, Veterinary Academy, Lithuanian University of Health Sciences, Tilžės 18, LT-47181, Kaunas, Lithuania. vita.riskeviciene@lsmuni.lt.
authors.forename: Vita
authors.initials: V
authors.lastname: Riškevičienė
authors.affiliation: Institute of Parasitology, Slovak Academy of Sciences, Hlinkova 3, Košice, 04001, Slovak Republic. varady@saske.sk.
authors.forename: Marian
authors.initials: M
authors.lastname: Várady
authors.affiliation: Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, P.O. Box 7028, SE-750 07, Uppsala, Sweden. johan.hoglund@slu.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Höglund
authors.affiliation: Department of Infectious Diseases, Veterinary Academy, Lithuanian University of Health Sciences, Tilžės 18, LT-47181, Kaunas, Lithuania. saulius.petkevicius@lsmuni.lt.
authors.forename: Saulius
authors.initials: S
authors.lastname: Petkevičius
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology*; D001562:Benzimidazoles / Q000494:pharmacology; D004351:Drug Resistance; D005767:Gastrointestinal Diseases / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D066298:In Vitro Techniques / Q000662:veterinary*; D007783:Lactones / Q000494:pharmacology; D008097:Lithuania / Q000453:epidemiology; D009348:Nematoda / Q000187:drug effects*; D009349:Nematode Infections / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D015995:Prevalence; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology* / Q000469:parasitology
chemical_list: D000871:Anthelmintics; D001562:Benzimidazoles; D007783:Lactones