Confirmation that the dog is a definitive host for Neospora caninum.

Two mixed-breed littermate dogs were fed mouse brains containing tissue cysts of the NC-beef isolate of Neospora caninum. Both dogs excreted N. caninum oocysts in their feces. Dog 1 which was given methylprednisolone acetate (MPA) prior to ingesting tissue cysts, excreted oocysts on days 5 to 10 inclusive and on day 17 after ingesting tissue cysts. Dog 1 had a serum antibody titer of 1:200 in the indirect fluorescent antibody test (IFAT) 35 days after it was fed tissue cysts. Dog 2, which was not treated with MPA, excreted oocysts on Day 6 and Day 9 after ingesting tissue cysts. Antibodies to N. caninum were not found in a 1:25 dilution of serum on any examination period for Dog 2 during the study. Neospora caninum was not found in the tissues of either dog by histological or immunohistochemical means following necropsy 42 days after being fed tissue cysts. The identity of the oocysts excreted in the feces of the dogs was confirmed by mouse inoculation studies.