Ehrlichial diseases

Equine granulocytic and monocytic ehrlichiosis caused by Ehrlichia equi and E. risticii, respectively, are seasonal diseases in horses that occur thro ughout the United States E. equi is transmitted by Ixodes ticks and causes high fever, depression, anorexia, limb edema, petechiation, icterus, ataxia , and stiffness in gait. E. risticii, also known as the agent of Potomac ho rse fever, causes a febrile illness with a colitis of variable severity. It s occurrence is associated with aquatic habitats. The natural route of tran smission is oral, through the ingestion of E. risticii infected trematode s tages either free in water or in an intermediate host, such as aquatic anim als.