Neosporosos has been described an important cause of abortion in cattle worldwide. Cattle may be infected transplacentally or as result of ingesting oocyst produced by dogs, which represent the definitive host. Cattle at any age may abort from three months of gestation to term, and abortion is the main clinical sign observed. Fetuses may die in utero, be resorbed, mummified, autolyzed, stillborn, born alive, but diseased or born clinically normal, but chronically infected. Although ,high prevalence of Neospora caninum infection were reported in dairy cattle in Iran. ,But, There is a little data about abortion due to N.caninum in dairy cattle in Iran. In this study, thoracic and abdominal fluids from 115 aborted bovine fetuses were evaluated for IgG antibody by the commercially available ELISA kit between 2006 and 2007 in Mashhad area. N. caninum antibodies were found in 18(15.65%) of body fluids of bovine fetuses. the result of this study confirms the role of N.caninum as a cause of abortion in dairy cattle in Iran and need to use developed technique such as PCR and IHC to increase the chance to detect the infection in aborted fetuses

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