title: The effects of chemoprophylaxis on acquired immunity against gastrointestinal nematodes in cattle.
abstract: The level and duration of exposure to gastrointestinal nematode infections are of crucial importance for the development of acquired immunity in first season grazing calves. An excessive reduction of host-parasite contact by chemoprophylaxis, pasture management, or both, causes a diminished level of acquired immunity. Moreover, the level of acquired resistance is negatively related to the degree of suppression of host-parasite contact. Whether or not a reduced resistance against establishment and development of gastrointestinal nematode infections has a negative effect on weight gain in the second grazing season, depends both on the intensity of the prophylaxis used and on the level of the challenge infection. Cross-sectional serological surveys and questionnaire surveys in The Netherlands, Germany and Belgium indicated that parasitic nematode control in first season grazing calves tends to be overprotective. Possible consequences of over-treatment, besides higher treatment costs and a reduced level of acquired immunity, are more drug residues in animal products and in the environment and increased selection for anthelmintic resistance.
authors.affiliation: Department of Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke.
authors.forename: E
authors.initials: E
authors.lastname: Claerebout
mesh_terms: D000818:Animals; D000969:Antinematodal Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control*; D004351:Drug Resistance; D007411:Intestinal Diseases, Parasitic / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D009349:Nematode Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D000969:Antinematodal Agents