Anthelmintic resistance and gastrointestinal nematodes control practices in sheep farms in Lithuania

Abstract

Anthelmintic resistance (AR) of gastrointestinal nematodes (GIN) in sheep is one of the main problem worldwide. In Lithuania this issue is under monitoring as well. Factors, such as the intensive and incorrect use of anthelmintics led to the development of AR. The aim of the study was to assess the GIN control practices used by Lithuanian sheep farmers and to evaluate the prevalence of AR to ivermectin (IVM), benzimidazoles (BZ), levamisole (LEV). During 2019-2020 all members of the Lithuanian Sheep Breeders Association, representing in all territory of the country (193 members), were surveyed. The questionnaire was completed by 52 members (26,9% response rate). Based on results from the questionnaire sheep were treated on average 1,52 times per year. Only 5,8%of sheep breeders regularly monitor GIN infection by fecal egg count test. IVM was the most frequently used anthelmintic – 63,5%. Selected farms were invited for AR studies. In vitro micro-agar larval development test was used to evaluate the prevalence of AR in 35 sheep farms. Results indicated a widespread resistance against IVM in 14 farms (40.0%) and BZ in 12 farms (34.3%). Resistance to LEV was not indicated. In 7 farms multidrug resistance was detected. In conclusion, AR of GIN is common in Lithuania, especially resistance to IVM. IVM is also the most commonly used in Lithuania. This study provides information about prevalence of AR and GIN control practices which could help to develop sustainable GIN control practices in sheep farms in Lithuania.