Histopathological and clinical investigations in Neospora caninum experimentally infected broiler chicken embryonated eggs

Abstract

To date, despite the limited information about the role of birds in Neospora caninum infection, there are no reports regarding the role of broiler chickens. In the present study, an experimental infection with N. caninum NC-1 isolate was conducted in embryonated eggs from 70 Lohman broiler chickens randomly divided into seven equal groups. At 8 days of incubation, six groups were inoculated via chorioallantoic (CA) liquid with different dilutions (10, 10 2, 10 3, 10 4, 10 5, and 10 6) of tachyzoites/embryonated egg. The 7th group was considered the control. The mortality rate, gross and histopathologic changes of tissues of the dead embryos and live hatched chickens up to 60 days old were studied and evaluated. There were no hatchings in groups with 10 5 and 10 6 tachyzoites. In groups with 10, 10 2, 10 3 and 10 4 tachyzoites there were 8, 7, 5 and 2 hatchings, respectively. From the surviving chickens only one 10 4 tachyzoites inoculated chicken showed clinical neurologic signs. In all groups the main gross lesions were hemorrhage associated with thickening of the CA membranes. Three chickens (one chicken with 10 4 tachyzoites and two with 10 5 tachyzoites) showed arthritis in the feet joints after two weeks of inoculation. Microscopic examination of the heart, liver and chorioallantoic membrane revealed acute neosporosis and, in some cases, granulomatous inflammation. Our findings implied that broiler chicken embryonated egg is a completely suitable animal model for biological studies of acute neosporosis studies and genetic susceptibility can be propounded in different chicken breeds. It seems 10 3 tachyzoites dilution is equal to LD50 in N. caninum infection in broiler chicken embryonated eggs and can be used in other experimental investigations.