Farm Table says:
Prevalence and distribution of gastrointestinal nematodes on 32 organic and conventional commercial sheep farms in Ontario and Quebec, Canada (2006–2008)
Gastrointestinal parasitism is an important animal health issue in grazing ruminants worldwide. In sheep, gastrointestinal nematodes (GINs) reduce farm income due to decreased productivity and increased disease control costs. In locations with a temperate climate similar to Ontario and Quebec, Teladorsagia circumcincta is considered one of the most important nematode species, but Haemonchus contortus has been reported in many such areas during the summer season.
Materials and Methods:
In order to characterize the epidemiology of sheep gastrointestinal nematodes in organic and conventional flocks in Canada, a longitudinal study was carried out from May 2006 to March 2008 on 32 purposively selected farms in Ontario (ON) and Quebec (QC):
• 8 certified organic (CO), 16 non-certified organic (NCO), and 8 conventional (C) farms. On each farm, 10 ewes and 10 female lambs were selected.
• Farm visits were undertaken monthly during the grazing season, and twice in the winter.
• At each visit, individual fecal samples were taken, and pasture samples were obtained during the grazing season.
• In addition, body condition score was recorded for all sheep.
• Fecal egg counts per gram of feces (Eggs Per Gram) were determined for all fecal samples, and infective larvae (L3) were identified in fecal samples (lambs and ewes separately) and pasture samples from farms.
• Necropsies of 14 lambs from 7 of the 23 Ontario farms were performed at the end of the grazing season in 2006.
Result Discussion and Conclusion
Although the overall mean EPGs were not remarkably high, there were months of higher EPG such as May–June for ewes and July–August for lambs in both provinces.
• Pasture infectivity was highest in May-June and September.
- June–July (984 L3/kg DM) in ON farms
- September (mean = 436 L3/kg DM) in QC farms
- October in ON (mean = 398 L3/kg DM)
- July in QC (239 L3/kg DM).
• Gastrointestinal nematode genera identified from fecal samples
Trichostrongylus axei and Trichostrongylus colubriformis were the species most frequently identified from necropsies (36.44% and 38.26%, respectively) at the end of the grazing season in 2006, with Haemonchus contortus and Teladorsagia circumcincta being the next most commonly identified.
• There was a general trend for the CO farms to have lower mean EPG than NCO and C farms.
In conclusion, results from this study provide an update on the epidemiology of GIN for the particular climatic regions of Ontario and Quebec. GIN was present throughout the grazing season regardless of operation type, with FECs peaking in the spring for the ewes, and in the summer for lambs, while pasture larval counts generally peaked in the summer/fall.