Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 8 1 2013 03 15 99 106 EN M Namavari Razi Vaccine and Serum Research Institute, Shiraz, Iran. A Oryan Department of Pathology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. F Namazi Department of Pathology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. M Kargar Department of Pathology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. M Mansourian Razi Vaccine and Serum Research Institute, Shiraz, Iran. A Rahimian Razi Vaccine and Serum Research Institute, Shiraz, Iran. Y Tahamtan Razi Vaccine and Serum Research Institute, Shiraz, Iran. 2015 10 14   Background: Caprine besnoitiosis is an economically important disease of goats. Neospora caninum, another coccidian parasite of worldwide distribution, infects several animal species and is a major cause of abortion in cattle. Combined infections of N. caninum and Besnoitia caprae can occur in geo-graphical areas endemic for both species of parasite in goats. This experiment was conducted to in-vestigate the possible cross-immunity between these two infections in experimentally infected BALB/c mice. Methods: Forty BALB/c mice were divided into four equal groups. The mice of Groups 1 and 4 were inoculated with 1×106 live virulent tachyzoites of N. caninum (NC-1), while animals of Groups 2 and 3 were inoculated with sterile tissue culture medium. Each mouse in Groups 1 and 2 was chal-lenged 28 days later with 1×106 live virulent bradyzoites of B. Caprae (BC-1). Results: Following the challenge, the mice in Groups 1 and 2 showed 100% morbidity and 100% mortality within 9 days post infection, while all the animals of Groups 3 and 4 remained alive. The dead animals were necropsied. The survivors (mice in Group 3 and 4) were euthanized 9 days after inoculation and the gross and histopathological lesions in different organs were investigated. Conclusion: Immunization and challenge experiments with lethal dose of B. caprae in the highly sus-ceptible BALB/c mice showed no cross-protection between N. caninum and B. caprae. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/519 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/519/399