(From Micro, 27 Oct 2000, by Brian Buschman)
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Rickettsia is an obligate intracellular parasite just like Chlamydia. It needs the cell’s ATP to live. It is always transmitted by some little bug except in the case of Q-fever caused by Cotiella burnetti.
Oddly enough they seem to have some antigens in common with Proteus vulgaris being OX-2, OX-19, OX-K. The Weil-Felix reaction is the test used to look for these antigens and is one way to ID Rickettsia. Other diagnostic methods include CF, immunofluorescence and ELISA.
Rocky mountain spotted fever is caused by Rickettsi rickettsii. It is seen mostly in the Appalachian region and is spread by ticks.
It causes the classic spots on the palms and sloes that usually resolve about three weeks after onset but may progress to death. It also has headache and fever. The redness is caused because it proliferates in the endothelium causing small hemorrhages making the rashes.
Rechettsial pox (like chicken pox) are caused by Rickettsia akari and are spread by rodent bites.
Epidemic typhus is from R. prowazekii. It kills many people in unsanitary conditions like war. It shows a pink rash that covers the body and causes it coagulation. The coagulation leads to peripheral gangrene.
It can be cured and can resurface years later if not treated properly. It’s recurance is called Brill-Zinsser disease. You can detect this from the original by looking for IgG rather then IgM.
It is strange that R. typhi is not epidemic but causes endemic typhus which is transmitted from rodents to us by tics.
R. tsutsugamushi is the Rickettsia of Asia and spreads by chigger bites.
Q-fever is caused by Cotiella burnetti. It is not a real Rickettsia because it has endospores and is not passed by an insect. Patients can inhale the spores and get a pneumonia. It is the only Rickettsia type bug that does not cause a rash.
Bartonella quintana causes trench fever. It is not an obligate intracellular but is spread by the louse and causes the classic Rickettsia presentation (headache, fever and rash). B. quintana is most often seen in soldiers in the trench.
Ehrlichia is a disease of dogs that looks like rocky mountain spotted fever. It is transmitted from the dog to humans by tics and Ehrlichia infects leukocytes.
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