Dynamics of anti-Neospora caninum antibodies during gestation in chronically infected dairy cows C. Nogareda a , F. Lo ´pez-Gatius a, * , P. Santolaria b , I. Garcı ´a-Ispierto c , G. Bech-Sa `bat a , M. Pabo ´n c , M. Mezo d , M. Gonzalez-Warleta d , J.A. Castro-Hermida d , J. Ya ´niz b , S. Almeria c,e a Department of Animal Production, University of Lleida, Spain b Department of Animal Production, University of Zaragoza, Huesca, Spain c Department of Anatomy and Animal Health, Autonomous University of Barcelona, Bellaterra, Barcelona, Spain d Agrarian Research Center of Mabegondo (CIAM), La Corun ˜a, Spain e Research Centre in Animal Health (CReSA), Autonomous University of Barcelona, Bellaterra, Barcelona, Spain Received 27 April 2007; received in revised form 20 June 2007; accepted 21 June 2007 Abstract The dynamics of antibody production against Neospora caninum during the gestation period was examined in chronically infected dairy cows. Data were obtained from 86 pregnant parous dairy cows, 21 of which had suffered abortion. The cows belonged to two herds in which a diagnosis of N. caninum infection had been previously confirmed in aborted foetuses. Pregnancy diagnosis and blood collection were performed on post-insemination Days 40, 90, 120, 150, 180, 210, and at parturition or until the time of abortion detection. Blood plasma was tested for antibodies against N. caninum using ELISA. The non-aborting cows were divided into two groups according to whether their antibody values in the second half of gestation had increased or not, while aborting cows were classified as those showing an antibody peak before abortion or those not showing a pre-abortion peak. Differences in antibody values throughout pregnancy in each group of non-aborting and aborting cows were analysed by GLM repeated measures of analysis of variance. While 32 non-aborting cows (49%) showed a significant and consistent increase in anti-Neospora antibody values during the second half of gestation, antibody values in the remaining 33 non-aborting cows were practically constant throughout gestation. An antibody peak around abortion was observed in 11 aborting cows (52%), while antibody values in the remaining 10 aborting cows were similar before and at abortion. Seroprevalence fluctuations, defined as seronegative blood samples at some point during the gestation period, were, furthermore, observed in 2 aborting and 11 non-aborting cows. Our results indicate two clearly distinguishable types of humoral immune dynamics throughout gestation: an increased or flat production of antibodies during the second half of gestation in non-aborting animals and before abortion in aborting cows. The observation that some Neospora-infected dams can exhibit negative antibody values at any time during gestation, particularly at parturition or abortion, prompts future studies designed to explore the use of new ELISA strategies at the farm level. # 2007 Elsevier B.V. All rights reserved. Keywords: Neospora caninum; Antibody response; Gestation; Dairy cows 1. Introduction Neospora caninum is an obligate intracellular parasite recognized, since its link with abortion in the late 1980s, as a major cause of abortion and reproductive failure in www.elsevier.com/locate/vetpar Veterinary Parasitology 148 (2007) 193–199 * Corresponding author at: Departament de Produccio ´ Animal, UdL, ETSEA, Avda. Rovira Roure 191, 25198 Lleida, Spain. Tel.: +34 973 70 25 00; fax: +34 973 70 28 74. E-mail addresses: flopez@prodan.udl.cat, flopez@prodan.udl.es (F. Lo ´pez-Gatius). 0304-4017/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2007.06.032