New Taxonomy of the Family Anaplasmataceae

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Table of Contents:
Introduction to ehrlichiae
Human Ehrlichiosis
General Characteristics of Ehrlichiae
Phylogram of the Family Anaplasmataceae
New Taxonomy of the Family Anaplasmataceae
Epidemiology
EM picture of Ehrlichia chaffeensis
 

Species

Common name of diseases

Common natural hosts

Cells most commonly infected

Primary vectors

Distribution
Ehrlichia chaffeensis Human monocytic (monocytotropic) ehrlichiosis (HME) Human, Dogs, deer Primarily mononuclear cells Lone Star Tick (Amblyomma americanum) USA, Europe, Africa, South and Central America
Anaplasma phagocytophilum (previous name: HGE agent, E. equi, E. phagocytophilum) Human granulocytic (granulocytotropic) ehrlichiosis (HGE), Equine ehrlichiosis, Tick-borne fever; pasture fever Human, Deer, wild rodents, elk, Horses, llamas, Sheep, cattle, bison, deer Granulocytes Ixodes scapularis and  I. pacificus in the USA; I. ricinus in Europe, transstadial USA, Great Britain, Europe
Neorickettsia risticii (previous name: E. risticii) Potomac horse fever, equine monocytic ehrlichiosis Horse Mononuclear cells Trematode in snails, aquatic insects USA
Ehrlichia canis Canine ehrlichiosis Dogs, wolves, jackals Primarily mononuclear cells Rhipicephalus sanguineus (tick), transtadial Worldwide
Neorickettsia sennetsu (previous name: E. sennetsu) Sennetsu fever (rickettsiosis); glandular fever Human Mononuclear cells Trematode in fish Japan, Malaysia
Ehrlichia ewingii Canine and Human granulocytic ehrlichiosis Human and Dogs Granulocytes Lone Star Tick (Amblyomma americanum) USA
Ehrlichia muris Unknown Rodents Mononuclear cells Haemaphysalis spp. Japan
Anaplasma platys (previous name: "E. platys") Canine cyclic thrombocytopenia Dogs Platelets Rhipicephalus sanguineus USA, Japan, Venezuela, Thailand, Europe, Taiwan, Greece, Israel
Ehrlichia ruminantium (previous name: Cowdria ruminantium) Heartwater Cattle, sheep, goat Endothelial cells Amblyomma ticks, transovarial Africa, Caribbean
Neorickettsia helminthoeca Salmon Poisoning Dogs Macrophages Nanophyetus salmincola (fluke), transovarial in fish Northern California, Washington, Oregon, Idaho
"SF Agent" Unknown Unknown Unknown Stellantochasmus falcatus (fluke) in fish Japan
Anaplasma marginale Bovine Anaplasmosis Ruminants Red blood cells Various tick sp. World Wide
Wolbachia pipientis Insects, non-insect invertebrates including nematodes, mites and spiders Unknown Unknown Various arthropod, nematode World Wide
 

Notes:

  • The Family Anaplasmataceae now contains four genas: Ehrlichia, Anaplasma, Neorickettsia, and Wolbachia.
  • The names of the organisms that enclosed in quotation marks have not been formally proposed and accepted according to the rules of the International Code of Nomenclature of Bacteria, Bacteriological Code. 
  • The ehrlichiae were initially grouped according to the type of blood cell most commonly infected (granulocyte, lymphocyte, monocyte, platelet), and disease classes have been termed "granulocytic (or granulocytotropic) ehrlichiosis" or "monocytic (or monocytotropic) ehrlichiosis." However, this type of classification may be misleading because some of the Ehrlichia species have been found in cells other than their chief target cell type. In addition, more than one species may be responsible for the broad category of "monocytic" or "granulocytic" ehrlichiosis.
  • Classification and Nomenclature changes for Ehrlichia and related species:
    • The Tribe Ehrlichieae and the genus Wolbachia are indeed in the Family Anaplasmataceae.
    • HGE agent, Ehrlichia equi, and E. phagocytophila become Anaplasma phagocytophilum.
    • Ehrlichia platys becomes Anaplasma platys.
    • Ehrlichia senetsu and E. risticii become Neorickettsia sennetsu and N. risticii respectively.
    • Cowdria ruminantium becomes Ehrlichia ruminantium.
    • Haemobartonella and Eperythrozoon sp. become Mycoplasma spp.

Source:

  1. Yasuko Rikihisa. 1996. Ehrlichiae. In "Rickettsiae and Rickettsial Diseases", Proceedings of the Vth International Symposium. Stara Lesna, Sept. 1-6, 1996.
  2. Dumler, J. S., A. F. Barbet, C. P. J. Bekker, G.A. Dasch, G. H. Palmer, S. C. Ray, Y. Rikihisa, and F.R. Rurangirwa (2001) Reorganization of Genera in the Families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales; Unification of some species of Ehrlichia with Anaplasma, Cowdria with Ehrlichia, and Ehrlichia with Neorickettsia; Description of six New Species Combinaions; and Designation of Ehrlichia equi and "HGE agent" as Subjective Synonyms of Ehrlichia phagocytophilum. Int. J. Syst. Evol. Microbiol. 51: 2145-2165.
  3. CDC (Human Ehrlichiosis in the United States).