Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 10 1 2015 03 15 96 101 EN Silvia Špilovská Institute of Parasitology of the Slovak Academy of Sciences, Košice, Slovak Republic. Katarína Reiterová Institute of Parasitology of the Slovak Academy of Sciences, Košice, Slovak Republic. Daniela Antolová Institute of Parasitology of the Slovak Academy of Sciences, Košice, Slovak Republic. 2015 10 14   Background: Neospora caninum is considered one of the major causes of repeated abortions in livestock. This study aimed to determine the seropositivity to N. cani-num using indirect ELISA and the influence of the infection on the occurrence of abortions in selected dairy herd in Slovakia. Method:Blood samples were obtained from 490 cattle over a period of two years and were tested for N. caninum antibodies using indirect ELISA. Results:The presence of specific antibodies in the herd was detected in 118 (24.1%) cows. According to selected groups; 117 (41.0%) cows with a history of abortion, 65 (43.3%) heifers and 223 (2.2%) cows without abortions were tested positive to Neospora. Vertical transmission of N. caninum dominated in examined herd and the relative risk (RR) of dam-daughter seropositivity in progenies of sero-positive mothers was 2.1 times higher than in progenies of seronegative dams. Mo-lecular analyses of aborted foetuses of seropositive mothers showed the presence of Neospora DNA. However, 23 (28.1%) of heifers born to seronegative cows were seropositive, indicating also the postnatal transmission of the infection from the environment. Conclusion:Study revealed significant correlation between the presence of specif-ic antibodies and the occurrence of abortions, the risk of abortion in seropositive animals was 3.8 times higher than in seronegative ones. Incorrect farm manage-ment contributed to spread and circulation of neosporosis in entire dairy herd what could significantly impair the reproduction and economic parameters of breeding. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/347 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/347/427