Veterinary Parasitology 209 (2015) 108–116 Contents lists available at ScienceDirect Veterinary Parasitology jou rn al hom epage : www.elsevier.com/locate/vetpar Prevalence and seasonality of bulk milk antibodies against Dictyocaulus viviparus and Ostertagia ostertagi in Irish pasture-based dairy herds Yris Bloemhoff a , Andrew Forbes b , Barbara Good c , Eric Morgan d , Grace Mulcahy e , Christina Strube f , Ríona Sayers a,∗ a Animal and Bioscience Research Department, Animal & Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland b Merial, 29 Avenue Tony Garnier, 69007 Lyon, France c Animal and Grassland Research and Innovation Centre, Teagasc, Athenry, Co. Galway, Ireland d School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, United Kingdom e School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland f Institute for Parasitology, University of Veterinary Medicine Hannover, Buenteweg 17, 30559 Hannover, Germany a r t i c l e i n f o Article history: Received 17 November 2014 Received in revised form 22 January 2015 Accepted 26 January 2015 Keywords: Dairy herds Ireland Dictyocaulus viviparus Ostertagia ostertagi Bulk milk a b s t r a c t Infections with Dictyocaulus viviparus and Ostertagia ostertagi nematode parasites are of importance to bovine health and production in temperate areas across the world. Losses due to these parasites in dairy herds can be considerable due to decreased milk productivity and fertility. However, information on current epidemiological patterns in Irish dairy herds is limited. Bulk milk samples were collected from a total of 319 dairy farms across the Republic of Ireland. The D. viviparus samples were tested with an ELISA based on recombinant major sperm protein, while the O. ostertagi samples were tested with an ELISA based on crude saline extract, whole worm O. ostertagi antigen. Management data were collected from the farms using a questionnaire. Logistic regression was used to find significant associations between the presence of antibodies against D. viviparus and O. ostertagi and management factors. The overall prevalence of D. viviparus infection was 62.8%, while over 98% of herds had antibodies to O. ostertagi at the specified cut-off. Both D. viviparus and O. ostertagi antibodies were highest in November, which could be explained by the accumulated uptake of larvae through the grazing season. In herds of farmers that dosed their in-calf heifers with anthelmintics were significantly more likely to be positive for antibodies against D. viviparus infection. This study highlights that both D. viviparus and O. ostertagi infections are widespread in dairy herds in Ireland throughout the grazing season. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Dictyocaulus viviparus and Ostertagia ostertagi infec- tions in dairy cows are generally of a subclinical nature, ∗ Corresponding author. Tel.: +353 25 42 215. E-mail address: riona.sayers@teagasc.ie (R. Sayers). particularly in the case of O. ostertagi. Recognition of infec- tion with these nematode parasites, therefore, can be difficult (Bennema et al., 2009; Perri et al., 2011). Tradition- ally diagnostics of these parasites were performed using corpological techniques, however, the use of low-cost and practical bulk tank milk (BTM) enzyme-linked immunosor- bent assays (ELISA), has eased diagnosis and determination of herd antibody status (Charlier et al., 2005b, 2010; Klewer http://dx.doi.org/10.1016/j.vetpar.2015.01.021 0304-4017/© 2015 Elsevier B.V. All rights reserved.