Technical Abstract: Since its first description in dogs in 1984, the protozoan parasite Neospora caninum has been found to infect a wide range of animals, worldwide. In cattle N. caninum has particular significance as a cause of abortion in which persistence of infection in the mother, recrudescence of the parasite during pregnancy, and the vulnerability of the placenta and foetus to invasion are all important features. The authors here discuss how Neospora invades cells and its ability to infect and cause disease in several animal species, but particularly how, in cattle and dogs, it has evolved a special niche ensuring its survival.