Evaluation of Cross Immunity and Histopathological Findings in Experimentally Infected BALB/c Mice with Neospora caninum and Besnoitia caprae

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 geographi­cal areas endemic for both species of parasite in goats. This experiment was conducted to investigate the possible cross-immunity between these two infections in experimentally infected BALB/c mice. 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 chal­lenged 28 days later with 1×106 live virulent bradyzoites of B. Caprae (BC-1). 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. Immunization and challenge experiments with lethal dose of B. caprae in the highly suscepti­ble BALB/c mice showed no cross-protection between N. caninum and B. caprae.