Overwintering of sheep gastrointestinal nematodes: Can roundworms survive the winter in Canada?

GURWITZ, TALIA; FERNÁNDEZ, ALICIA SILVINA; MENZIES, PAULA; PEREGRINE, ANDREW

Guelph

Jornada; OVC Summer Leadership Program Poster Presentations 2008; 2008

University of Guelph

There are six genera in the Trichostrongylidae family that have been found infecting Canadian sheep and they all exhibit similar life cycles. Although it has been previously shown that nematodes such as Trichostrongylus spp., Teladorsagia spp., and Nematodirus spp. can survive Quebec winter, current management practices assume that winter weather conditions have killed any L3 left on pasture the previous fall. Haemonchus spp., arguably the deadliest of the sheep gastrointestinal nematodes, has always been considered unablet o overwinter on pasture due to its ecological adaptation to much warmer climates. This study investigated the prevalence and type of gastrointestinal nematode survival on overwintered pastures in the provinces of Ontario and Quebec. Grass samples and sheep faecal pellets were collected in April and/or May 2008 from pastures on 18 sheep farms in Ontario and 9 in Quebec, which had not been grazed since late October-early December 2007. Infective nematode larvae were extracted from both types of samples, counted and identified. Meteorological data was collected from the weather stations closest to each farm for the period October 1, 2007 to April 30, 2008. Of the 27 farms studied, 59& showed overwintering parasites in faeces and/or in grass samples. Teladorsagia was found on 48% of pastures samples (in faeces and/or grass), Haemonchus was found on 26% of the farms sampled. Other genera identified were Trichostrongylus (37%), Cooperia (4%), and Oesophagostomum/Chabertia (19%). The studi demonstrated that infective larvae of several gastrointestinal nematode genera can survive on pasture during Canadian winters. Moreover, the levels of parasites on pasture were higher than generally believed by practitioners, extension personnel and producers in the sheep industry. The study also supports previous findings that Haemonchus spp. can overwinter to potentially infect a flock turned-out to spring grazing in the Canadian regions studied.