Parasite control practices on pasture-based dairy farms in the Republic of Ireland

Dictyocaulus viviparus, Ostertagia ostertagi (nematode parasites), and Fasciola hepatica (trematode parasite) result in productivity losses on dairy farms and impact on animal health through clinical and sub-clinical disease. Parasite control in livestock systems is largely based on the use of chemoprophylactic agents (anthelmintics), grazing management, or a combination of both. The objective of this study was to document current parasite control measures employed by Irish dairy farmers in a predominantly pasture-based livestock system. A questionnaire survey of 312 geographically representative farmers was completed in 2009 with a follow up survey completed in 2011. Statistical analysis highlighted significant differences in chemoprophylactic usage between 2009 and 2011. In particular, an increase in the use of albendazole for both trematode (19% in 2009 to 36% in 2011) and nematode (30% in 2009 to 58% in 2011) control was observed. This was most likely due to flukicide restrictions introduced in the Republic of Ireland in 2010 for dairy animals. Logistic regression highlighted regional differences in chemoprophylactic use. Farmers in southern parts of Ireland, an area with good quality soil, less rainfall, and a higher density of dairy farms than other regions, were approximately half as likely to dose for F. hepatica and were more likely (OR > 2.0) to use albendazole for both nematode and fluke control. Approximately 30% of respondents who used a chemoprophylactic treatment for nematodes, used a product which was 'unsuitable for purpose' (e.g. ivermectin for the treatment of F. hepatica), highlighting the need for increased awareness, continuing research, and regionally targeted education tools regarding optimal parasite control.