In Vitro Evaluation of Benzimidazole Resistance of Ancylostomidae şi Strongylididae in Dogs Cristina L. CERNEA, Mihai CERNEA University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine, 3-5 Manastur street, 3400, Cluj-Napoca, Romania, e-mail: mscernea@yahoo.com Abstract. To test in vitro efficacy of Mebendazole (MBZ), Fenbendazole (FBZ) and Albendazole (ABZ) using egg hatch assay in ancilostomosis and strongyloidiasis in dogs, a number of 62 animals has been studied from Cluj-Napoca, Floreşti, Tg. Mureş. The ante- therapeutic epidemiology survey conducted revealed that from the total number of dogs taken into the study only 41.93% received annual or biannual anthelmintic treatment. The anthelmintic medication products used were based on benzimidazole derivatives (24.19% of cases). In the case of samples collected form the dogs located in Cluj-Napoca and Floreşti, the Mebendazole was most effective taking into account the LC 50 , which had the lowest value (-0.2352μg/ml respectively -0.1405μg/ml). However the maximum Y parameter was recorded at Fenbendazole (-1538.57 respectively -1754.82). In samples collected from dogs located in Tg. Mureş the maximum efficacy was recorded at Fenbendazole with LC 50 of -0.1052μg/ml and Y of -1880.42. Keywords: dog, helmints, bezimidazole, resistance INTRODUCTION Taking into account the very high risk of human contamination with Ancylostomidae and Strongylididae species from dogs, should be more precise knowledge of the effectiveness of medications used in prevention and treatment of both diseases. Lack of anthelmintic medication applied periodically or use without further verification of the effectiveness of treatment, determines a major risk for the occurrence of zoonosis [Gent, 1989]. One method to verify the in vitro of efficacy of anthelmintic therapy is done by egg hatch assay - EHA [Glrud, 1993]. MATERIALS AND METHODS To test the in vitro effectiveness of Mebendazole (MBZ), Fenbendazole (FBZ) and Albendazole (ABZ) against dog ancilostomsis and strongiloidosis a number of 62 has been studied from: Cluj-Napoca, Floreşti, and Tg. Mureş. For each animal taken i n the study, the number of eggs/g (EPG) was determined through the McMaster method. The number of larvae/g (LPG) were quantify through the Stoll method adapted for quantitative larvo- helmintoscopy. The intensivity level was determined as well as the extensivity for dogs in each region. The in vitro testing of resistance was performed by egg hatch assay (EHA). This test consists of incubating parasite eggs in serial dilutions of a benzimidazole compound and then counting the proportion of eggs that were unable to generate embryos and/or hatched [Craven et al., 1999]. The incubation temperature was of 26C and the results were read after 24 hours. Helmint eggs were collected from fresh or stored in anaerobic conditions faeces. We used USP active drug substance (Sigma Chemical Company, St. Louis, MO, USA) diluted in DMSO and distilled water.