Veterinary Medicine - April 2008 - (Page 212)

CE PEER-REVIEWED An update on anaplasmosis in dogs This bacterial disease, caused by two different Anaplasma species, is spreading worldwide in dogs and has zoonotic potential. A. Rick Alleman, DVM, PhD, DABVP, DACVP, and Heather L. Wamsley, DVM, DACVP C anine anaplasmosis is caused by one of two gram-negative, obligate, intracellular bacterial agents, Anaplasma phagocytophilum or Anaplasma platys. Infection with A. phagocytophilum, the species more commonly associated with anaplasmosis, causes lameness and is often confused with Lyme disease. Infection with A. platys results in a cyclic thrombocytopenia. Both types of anaplasmosis are likely spread by ticks and can occur worldwide. A NOTE ON CLASSIFICATION Both A. phagocytophilum and A. platys are in the order Rickettsiales, which includes members of the genera Ehrlichia, Anaplasma, Cowdria, Wolbachia, and Neorickettsia. In 2001, a major restructuring of the classi cation of organisms occurred in the order Rickettsiales.1 As a result of these investigations, three separate species of Ehrlichia—Ehrlichia equi, Ehrlichia phagocytophila, and the previously unnamed agent causing human granulocytic ehrlichiosis—were found to be insuf ciently different to warrant separate species designations. These organisms were phylogenetically most closely related to species in the genus Anaplasma, so they were reclassi ed as A. phagocytophilum. In addition, Ehrlichia platys was found to be more closely related to Anaplasma species and was subsequently renamed A. platys.1 A. Rick Alleman, DVM, PhD, DABVP, DACVP Heather L. Wamsley, DVM, DACVP Department of Physiological Sciences College of Veterinary Medicine University of Florida Gainesville, FL 32608 ANAPLASMA PHAGOCYTOPHILUM INFECTION A hallmark of this form of anaplasmosis is that it may result in subclinical disease or a chronic carrier state. and Wisconsin in 1996.2 Anaplasma phagocytophilum infection is a vector-borne zoonotic disease, and its appearance in dogs in those areas closely coincided with recognition of the disease in people.3 The organism has a worldwide geographic distribution and is endemic in the upper Midwest, East, and Northeast regions of the United States as well as the western coastal regions. European countries such as the United Kingdom, Norway, Sweden, Switzerland, and Germany also have reported infections in ruminants, dogs, and people. The disease has been less frequently reported in Asia and South America. In the United States, most disease outbreaks are seasonal and coincide with the emergence of tick vectors in spring and early summer (May and June) and then again in the fall (September). Tick vector and mammalian hosts Several ixodid ticks can serve as vectors for A. phagocytophilum. In the United States, Ixodes scapularis is the primary vector in the upper Midwest and the Northeast, and Ixodes paci cus is the primary vector in the Illustration by Sandy Ostroff Epidemiology Infection with A. phagocytophilum was rst reported in dogs from Minnesota 212 April 2008 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - April 2008

Veterinary Medicine - April 2008 Contents Letters Leading Off The Veterinary Medicine Interview: Dr. Barrak Pressler Idea Exchange Help! My Dog Licks Everything An Update on Anaplasmosis in Dogs CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - April 2008

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