Neorickettsia is a genus of bacteria. Species or Strains in this genus are coccoid or pleomorphic cells that reside in cytoplasmic vacuoles within monocytes and macrophages of dogs, horses, bats, and humans. Neorickettsia sennetsu causes Sennetsu ehrlichiosis, Unlike most other closely related diseases, Neorickettsia sennetsu is transmitted by Trematodes from fish. while Neorickettsia risticii causes Potomac Horse Fever