title: Monthly fluctuations of worm burdens and hypobiosis of gastrointestinal nematodes of calves in extensive management systems in the Pyrenees (Spain).
abstract: Monthly fluctuations of worm burdens and arrested development of gastrointestinal nematodes in cattle from a mountainous region of Spain were studied. Fourteen previously helminth-naive calves grazed together with a herd of 120 cattle from May to November following the traditional extensive grazing system used in mountainous regions of Spain (permanent calves). Each month, throughout the grazing season, two helminth-naive calves (tracer calves) were added to the herd and allowed to graze for 4 weeks. Every 2 weeks, throughout the grazing period, faecal and blood samples from the permanent calves, and pasture grass samples for larval recovery were collected. Every 4 weeks, throughout the grazing period, two tracer and two permanent calves were removed from the herd and housed on concrete for 2 weeks before being slaughtered. The nematode parasite species identified from the animals were: Ostertagia ostertagi, O. lyrata, Teladorsagia circumcincta, Trichostrongylus axei, Cooperia oncophora, Trichostrongylus longispicularis, Capillaria bovis, Nematodirus helvetianus, Oesophagostomum radiatum, Chabertia ovina and Trichuris spp. O. ostertagi was the predominant species, followed by C. oncophora and T. axei. The highest numbers of worms recovered from the tracer calves were observed in May, June, September and November with average worm burdens of 4050, 3775, 2775 and 2825, respectively. These dates corresponded with 2 months of spring grazing in areas below 1000 m (May-June), the last month of grazing in areas higher than 1000 m (September), and the last month of autumn grazing in areas below 1000 m (November), respectively. The highest total worm burden (8000 worms per animal) was observed in the permanent calves in June after 2 months of grazing below 1000 m. The average total worm burden in the permanent calves during the study was 5825 worms per animal. As in other cool temperate regions of the Northern hemisphere, the highest percentage of larval inhibition was observed in autumn, with maximum levels of 63.4% for Ostertagia spp. and 89.3% for Cooperia oncophora. Similar inhibition levels were observed in parasites from both tracer and permanent calves, indicating that previous exposure was not the primary cause of larval inhibition.
authors.affiliation: Unidad de Sanidad Animal, Parasitología, Servicio de Investigación Agraria (D.G.A.), Zaragoza, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Almería
authors.forename: M M
authors.initials: MM
authors.lastname: Llorente
authors.forename: J
authors.initials: J
authors.lastname: Uriarte
mesh_terms: D000822:Animal Husbandry / Q000592:standards; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology*; D002980:Climate; D016266:Food Parasitology; D005767:Gastrointestinal Diseases / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D007814:Larva; D009348:Nematoda / Q000302:isolation & purification*; D009349:Nematode Infections / Q000453:epidemiology / Q000662:veterinary*; D010028:Ostertagia / Q000302:isolation & purification; D006109:Poaceae / Q000469:parasitology; D012621:Seasons; D013030:Spain; D014254:Trichostrongylus / Q000302:isolation & purification