Prevalence of anthelmintic resistance on Lithuanian sheep farms assessed by in vitro methods

Abstract

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.

Anthelmintic resistance in gastrointestinal nematodes in sheep raised under mountain farming conditions in Northern Italy

“…AR to a wide range of GIN in small ruminants were proven in a growing number of countries, such as England and Wales,19 France,3 Norway,4 Sweden,20 Denmark,5 The Netherlands,21 Germany,22 Austria,23 Switzerland,24 Lithuania6 and Slovakia 25. In Central Italy, Traversa and others2 already reported multiple ARs of gastrointestinal trichostrongylids in sheep.…”

A comparison of two different anthelmintic treatment regimens against natural gastrointestinal nematode infections on two Lithuanian sheep farms

“…The animals on all farms were examined for the presence of Fasciola and lungworm infection on two occasions (April and September). In addition, the parasites on all farms were examined before the study for the presence of ivermectin and benzimidazole resistance using in vitro methods [11, 17]. It was then confirmed that the nematode parasites were susceptible to both anthelmintics used in this study.…”

Prevalence of anthelmintic resistance of gastrointestinal nematodes in Polish goat herds assessed by the larval development test

“…This is the first study systematically investigating the prevalence of AR to three basic classes of anthelmintics in small ruminants in Poland. Similar surveys based on in vitro tests have so far been conducted in Europe on sheep flocks in Lithuania [ 9 , 34 ] and Ireland [ 35 ], and sheep and goat flocks in Slovakia [ 15 , 36 ]. Moreover, the LDT is a commonly applied technique in the AR prevalence studies in the United States [ 11 , 16 , 37 , 38 ], Philippines [ 39 , 40 ], Canada [ 41 ] and the New Zealand [ 42 , 43 ] in both goat and sheep flocks.…”