Evaluation of a predictive computer model for use in Canadian Sheep Flocks

GUTHRIE, ALESSIA; LEARMOUNT, JANE; PEREGRINE, ANDREW; KELTON, DAVID; VANLEEUWEN, JOHN; MENZIES, PAULA; FERNÁNDEZ, ALICIA SILVINA; MARTIN, RALPH; MEDEROS, AMÉRICA; TAYLOR, MIKE

Conferencia; 22nd Conference of the World Association for the Advancement of Veterinary Parasitology; 2009

With increasing levels of anthelmintic resistance worldwide and a growing demand to produce more organic products, utilisation of control strategies for gastrointestinal nematodes (GIN) that minimise the use of anthelmintics becomes even more important. This study evaluated the farm-level performance of an existing predictive sheep parasite model from the United Kingdom (UK), using Canadian data. The UK model, first introduced at WAAVP in 2005 by Taylor et al., simulates the epidemiology of three major GIN species of interest (Telodorsagia sp., Haemonchus sp. and Trichostrongylus spp.) and provides a prediction about seasonal parasite levels. Model inputs were generated by using data from the first year of a three year (2006-2008) study which examined the epidemiology of GIN parasitism in organic sheep flocks located in Ontario and Quebec. Required input data included ewe parasite egg output, pasture-related information, and management dynamics. Farm visits in 2006 provided relevant data that were collected monthly, on six occasions during the grazing season, from 10 ewes and 10 lambs on each farm. These values were compared against the model output and assessed using regression analysis (R>50%) to determine fit. Results for 2006 indicated that for 32 farms with available data, 10 had suitable data to run in the model. The number of unsuitable farm data can be explained by the fact that the Canadian study was not specifically designed with the model in mind. However, of these 10 suitable farms, approximately five showed reasonable fit within model. Required model modifications focused on accommodating the differences between UK and Canadian management styles; specifically the practice of bringing lambs indoors for weaning, which was occasionally used on Canadian farms.