Oocyst excretion in dogs fed mouse brains containing tissue cysts of a cloned line of Neospora caninum

Neospora caninum is an apicomplexan parasite that causes neonatal neuromusc ular disease in dogs and abortions in cattle. Bovine neosporosis is a major production problem worldwide. The parasite is transmitted to cattle via oo cysts excreted by dogs or by transplacental transmission. Dogs are the only proven definitive host for N. caninum. One of 3 dogs fed mouse brains cont aining tissue cysts of a wild-type N. caninum strain CK0160SC3B (CKO) excre ted oocysts in its feces. Two of 3 dogs fed mouse brains containing tissue cysts from a cloned line of the CKO strain excreted N. caninum oocysts in t heir feces. The results indicate that a single N. caninum tachyzoite contai ns all the genetic information needed to produce the asexual and sexual cyc les in the canine intestine.