Agents such as Brucella abortus, Salmonella Dublin, Leptospira harjo, Listeria monocytogenes, Aspergillus fumigatus, Neospora caninum, BVDv, BHV1,etc. are capable of crossing the intact placenta and causing placentitis, fetopathy or luteal regression due to their intrinsic virulence. They can be classified as primary abortifacients.
