Multiple Anthelmintic Resistance at a Goat Farm in Slovakia.

Cases of parasite resistance to the main classes of anthelmintics are increasingly reported from small ruminants at farms in Europe. We visited a goat farm in Slovakia in November 2019 with suspected parasite problems that reduced productivity and performed an in vivo faecal egg count reduction test (FECRT) and an in vitro larval development test (LDT) for all three main classes of anthelmintics. The lowest efficacy (60 %) detected by FECRT was for ivermectin (IVM). Benzimidazole (BZ) efficacy ranged between 80.3 and 86.5 %, and levamisole (LEV) efficacy was 94 %. The results from the in vivo FECRT test were confirmed by the in vitro LDT. Minimum inhibitory concentration (MIC) 173.6 ng/ml for IVM several times exceeded the recommended threshold of 21.6 ng/ml. Mean LD50 for BZ was equal to the threshold concentration, but the other threshold criteria indicated a low level of resistance in the population. The LDT did not indicate the presence of resistance only for LEV. The MIC 1.0 µg/ml for LEV was evaluated as susceptible with respect to species composition. Teladorsagia was the dominant genus after treatment with BZ, IVM, and LEV. Haemonchus contortus was identifi ed after treatment with BZ and LEV.

Development of resistance to eprinomectin in gastrointestinal nematodes in a goat herd with pre-existing resistance to benzimidazoles.

We described a first case of resistance to eprinomectin in goat herd in Poland in which resistance to benzimidazoles had been previously reported. The herd was established in 2011 by purchasing several goats from a single herd in south-eastern Poland. Resistance to benzimidazoles in the herd was first reported in 2017. Shortly after the owner started to signal low effectiveness of the treatment with eprinomectin. In June 2018 the larval development test from pooled faecal sample was performed and the results indicated the presence of resistance to macrocyclic lactones and levamisole. In July 2018 a faecal egg count (FEC) reduction test was performed in 39 animals with levamisole, eprinomectin and one untreated control group. Drugs were used in doses recommended for goats. Three methods of calculation of FEC reduction were compared. After eprinomectin treatment, FEC reduction ranged from 0 to 20%, depending on the method of calculation. FEC reduction following levamisole treatment was 100%. Main species present in the faecal samples after treatment and in larvicidal concentrations in larval development test was Haemonchus contortus. This is the first report of anthelminthic resistance to macrocylic lactones (eprinomectin) in goats in Poland.