title: Anthelmintic efficacy of oral trichlorfon solution against ivermectin resistant nematode strains in cattle.
abstract: Infected calves from two different rural estates in Brazil were studied to assess the anthelmintic efficacy of oral trichlorfon against naturally occurring ivermectin resistant parasitic nematode strains. In experiment I, infected animals were from a region where ivermectin resistant populations of Haemoncus placei, Cooperia punctata, Cooperia spatulata and Trichuris discolor have recently been identified. Six calves with natural gastrointestinal nematode infections were treated with 48.5mg/kg aqueous trichlorfon administered orally and six calves acted as a non-treated control group. In experiment II 24 naturally infected calves were selected to enter one of four treatment groups, six animals each received: 48.5mg/kg oral trichlorfon; 200 microg/kg subcutaneous 1% ivermectin; 630 microg/kg subcutaneous 3.15% ivermectin; or no treatment (control group). Gastrointestinal helminths were counted and identified post-mortem at 7 days (trichlorfon and 1% ivermectin treated and untreated animals) or 14 days (3.15% ivermectin treated and untreated animals) after administration of the test agents. Experiment I identified a high level efficacy for oral trichlorfon against four helminth species that have previously been shown to be ivermectin resistant in this geographical region: percentage efficacy was 99.82% against adult H. placei, 99.18% against C. punctata, 99.33% against C. spatulata, 81.06% against T. axei, 98.46% against Oesophagostomum radiatum and 100% against T. discolor. Trichlorfon also showed activity against the ivermectin (1% and 3.15%) resistant helminth species identified in experiment II, attaining efficacy levels of 99.17% against H. placei, 98.46% against C. punctata and 100.00% against T. discolor. These findings indicate that oral trichlorfon is an effective treatment option in the management of cattle infected with ivermectin resistant helminths.
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n, CEP:14884-900 Jaboticabal, São Paulo, Brazil. cppar@asbyte.com.br
authors.forename: Welber Daniel Zanetti
authors.initials: WD
authors.lastname: Lopes
authors.forename: Thaís Rabelo
authors.initials: TR
authors.lastname: dos Santos
authors.forename: Fernando de Almeida
authors.initials: Fde A
authors.lastname: Borges
authors.forename: Claudio A M
authors.initials: CA
authors.lastname: Sakamoto
authors.forename: Vando Edésio
authors.initials: VE
authors.lastname: Soares
authors.forename: Gustavo Henrique Nogueira
authors.initials: GH
authors.lastname: Costa
authors.forename: Gilberto
authors.initials: G
authors.lastname: Camargo
authors.forename: Mário Eduardo
authors.initials: ME
authors.lastname: Pulga
authors.forename: Chandra
authors.initials: C
authors.lastname: Bhushan
authors.forename: Alvimar José
authors.initials: AJ
authors.lastname: da Costa
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000469:parasitology; D004351:Drug Resistance; D005767:Gastrointestinal Diseases / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D007559:Ivermectin / Q000494:pharmacology / Q000627:therapeutic use; D009348:Nematoda / Q000187:drug effects / Q000502:physiology*; D009349:Nematode Infections / Q000188:drug therapy / Q000662:veterinary*; D011897:Random Allocation; D014236:Trichlorfon / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D000871:Anthelmintics; D007559:Ivermectin; D014236:Trichlorfon