TAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Alphaproteobacteria -> Rickettsiales -> Anaplasmataceae -> Ehrlichia
Ehrlichia is a genus of rickettsiales bacteria that is transmitted to vertebrates by ticks. This disease is considered zoonotic, because the main reservoir for the disease is animals.Ehrlichia are obligately intracellular pathogens and are transported between cells through the host cell filopodia during initial stages of infection, whereas, in the final stages of infection the pathogen ruptures the host cell membrane.The genus Ehrlichia is named after a German microbiologist Paul Ehrlich.The first ehrlichial disease was first recognized in South Africa during the 19th century. Its tick-borne nature was determined in 1900. The organism itself was demonstrated 1925 when it was recognized to be a rickettsia. It was initially named Rickettsia ruminantium, and is currently named Ehrlichia ruminantium. In 1945 a 'infection and treatment' method for livestock was developed. This is still the only commercially available 'vaccine' against the disease, which is not a true vaccine, but intentional exposure to the disease with monitoring and antibiotic treatment if needed. In 1985 the organism was first propagated reliably in tissue culture. A new species of Ehrlichia was discovered inside the deer tick Ixodes scapularis. This newly found organism has only been isolated from deer ticks in Wisconsin and Minnesota in the USA. The species is known as Ehrlichia Wisconsin HM543746.