Bacteria Genomes - EHRLICHIA CANIS

The Ehrlichiae are a group of small, gram-negative, pleiomorphic, obligate intracellular cocci that infect different blood cells in various animal species and in humans

Ehrlichia canis, a member of the order Rickettsiales, is a tick-borne small obligate intracellular, gram-negative, dimorphic bacterium that resides as a microcolony within a membrane-lined intracellular vacuole (morula), primarily in monocytes and macrophages of mammalian hosts. Each morula may contain 100 or more ehrlichiae. Ultrastructurally, E. canis has two forms, termed reticulate and dense-cored cells, resembling morphologically similar reticulate and elementary body forms of chlamydiae. Ehrlichiae have relatively small genomes (~1.2 Mbp) and do not possess extrachromosomal plasmids.

There are three main stages of canine monocytic erhlichiosis - acute, sub-clinical and chronic. Classically, canine ehrlichiosis presents as a rather non-specific multisystemic disorder with the primary complaints being depression, lethargy, mild weight loss, vomiting, diarrhea, and anorexia, with or without hemorrhagic tendencies. Other symptoms may include uveitis and/or retinal petechiae, polymyositis, polyarthritis, and central nervous system signs.

This organism is primarily transmitted by Rhipicephalus sanguineus, the brown dog tick. It is seen mostly in the southeastern and southwestern United States, although it is recognized in all states and worldwide. Infection occurs through salivary secretions of the tick at the attachment site during ingestion of a blood meal or through blood transfusions. If the adult Rhipicephalus sanguineus engorges on the dog during the acute stage, it can transmit the disease to other dogs for at least 155 days following detachment. Transmission by Rhipicephalus sanguineus is transstadial: the tick acquires the bacteria by feeding on an infected dog in either the larvae or nymph form and the tick transmits the disease to another dog as either the nymph or adult form.

Prevention is predominantly by tick control however E. canis is normally susceptible to treatment with tetracycline antibiotics.

References:

http://www.vet.uga.edu/vpp/clerk/Bockino/
http://pcwww.liv.ac.uk/testapet/Ehrlichia_6.htm
http://www.vetmed.wisc.edu/pbs/zoonoses/Ehrlichia/ehrcanisdogs.html