Prevalence of anthelmintic resistance on Lithuanian sheep farms assessed by in vitro methodsReport as inadecuate

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Acta Veterinaria Scandinavica

, 57:88

First Online: 16 December 2015Received: 16 September 2015Accepted: 04 December 2015


BackgroundThis 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.

ResultsBZ-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.

ConclusionsThe 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.

KeywordsAnthelmintic resistance In vitro Sheep nematodes Egg hatch test Larval development test  Download fulltext PDF

Author: Tomas Kupčinskas - Inga Stadalienė - Mindaugas Šarkūnas - Vita Riškevičienė - Marian Várady - Johan Höglund - Sauli



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