BACKGROUND: Neospora caninum is a protozoanintracellular parasite which is considered as one of the main factors forrecurrent abortions of dairy cattle in various countries such as Iran. Thisparasite leads to negative economic impacts such as decline in reproduction,reduced amount of milk, and long calving intervals. OBJECTIVES: Therehave been numerous tests to determine the cause of abortion. PCR test isconsidered as a suitable method to specify Neospora caninum DNA and itcan determine the DNA in tissue samples and body fluids of the aborted fetus.This study aims to use PCR to evaluate parasites in the tissues of abortedfetuses so as to detect the best tissue for determining the parasite. METHODS:In this study, 82 aborted fetuses in the first six months of 2015 were studied.The tissues were selected from brain, liver, lungs, spleen, kidneys and rennetfluids. The NP21plus primer was used to detect the presence of Neosporacaninum in samples. After conducting the PCR Test, samples with 340bp bandin Gel electrophoresis were considered as positive. Statistical data from thesurvey of Neospora caninum’s presence in selected tissues were evaluatedby SAS (version 9.2) software. RESULTS: Contamination with this parasitewas found in 34 brain samples (41.5%) of aborted fetuses. In 2 (2.4%) and 4(4.9%) of the aborted fetuses, parasite DNA was found in lung and liver tissuesalong with brain tissues, respectively. CONCLUSIONS: Due to significantdifference of infection of brain tissues in comparison to other tissues, ourstudy considers brain tissue as the most appropriate sample for detecting Neosporacaninum infection in aborted fetuses in PCR method

BACKGROUND: Neospora caninum is one of the most important pathogenic protozoan parasites causing bovine abortion around the world. Objectives: The aim of this study was to detect the presence of Neospora caninum in the brain, cerebellum and medulla oblongata of aborted fetuses in cattle in Arak by means of molecular method. Methods: 38 samples of brain, cerebellum and medulla oblongata from aborted fetuses in dairy cattle of Arak were tested for the presence of Neospora with nested-PCR. Results: Survey findings indicated the presence of DNA in 26.3 % of aborted fetal brains. In the cerebellum and medulla oblongata samples no Neospora caninum  DNA was detected. There was a significant relationship between neosporosis and maternal age (number of calvings), abortion history and the presence of dogs in the herd. Conclusions: The results showed a significant association between the infection and the number of abortions in the examined cows; As a result it seems that neosporosis could be an important factor in epidemic abortions in Arak city’s dairy farms which requires continuous monitoring and implementation of prevention programs in the dairy industry.