Microscopic protozoa and cysts. Sometimes white flecks on placenta. Cooler climates, associated with cats. White flecks on aborted placenta. Send placenta and serum from unfed lambs to laboratory.
Sheep are intermediate hosts.
Dog is the definitive host S. tenella , cat for S. gigantia and S. medusiformis . All are host specific. Indirect, Sheep infected by eating sporocysts in dog or cat faeces. These develop to the equivalent of a meront in walls of blood vessels and muscle. Muscle cysts are eaten by dogs or cats Where they pursue a coccidial cycle.