title: Multiple resistance of gastrointestinal nematodes to nine different drugs in a sheep flock in southern Brazil.
abstract: Based on clinical observation of a flock of approximately 5000 sheep (breed Merino) from southern Brazil, the failure of anthelmintic treatments was suspected. The sensitivity of the gastrointestinal nematodes that infected these sheep to nine drugs (Levamisole, Moxidectin, Albendazole, Ivermectin, Nitroxynil, Disophenol, Trichlorphon, Closantel, and a combination of Ivermectin, Levamisole and Albendazole) was evaluated. None of the drugs reduced the count of nematode eggs per gram of feces (EPG) in the sheep to an adequate extent (defined as a 95% reduction in EPG). Therefore, we found multiple parasite resistance to all classes of anthelmintic drugs available for small ruminants in the Brazilian market. The genera Haemonchus spp., Trichostrongylus spp. and Ostertagia spp. had various degrees of resistance (or natural tolerance) to each of the drug treatments.
authors.affiliation: Departamento de Medicina Veterinária Preventiva (DMVP), Centro de Ciências Rurais (CCR), Universidade Federal de Santa Maria (UFSM), 97105-900 Santa Maria, RS, Brazil. alfredosps@hotmail.com
authors.forename: Alfredo Skrebsky
authors.initials: AS
authors.lastname: Cezar
authors.forename: Gustavo
authors.initials: G
authors.lastname: Toscan
authors.forename: Giovana
authors.initials: G
authors.lastname: Camillo
authors.forename: Luís Antônio
authors.initials: LA
authors.lastname: Sangioni
authors.forename: Henrique Olmedo
authors.initials: HO
authors.lastname: Ribas
authors.forename: Fernanda Silveira Flôres
authors.initials: FS
authors.lastname: Vogel
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology* / Q000627:therapeutic use; D001938:Brazil / Q000453:epidemiology; D018432:Drug Resistance, Multiple; D007814:Larva / Q000187:drug effects; D009348:Nematoda / Q000187:drug effects*; D009349:Nematode Infections / Q000188:drug therapy / Q000453:epidemiology / Q000662:veterinary*; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy / Q000453:epidemiology / Q000469:parasitology*
chemical_list: D000871:Anthelmintics