Snapshot A five-year-old boy presents to a hospital in Spain with a five-day-history of fever, abdominal pain, myalgia, and skin rash. There is a history of similar illness in his older brother. Blood and urine cultures, tests for Plasmodia, Widal test, and IgM ELISA for leptospirosis all proved negative. Further questioning revealed a history of close contacts with dogs and a recent tick bite on one hand. Weil-Felix test was positive and samples were sent for PCR and immunohistochemistry. Introduction Classification bacteria Rickettsia R. rickettsii R. typhi R. prowazekii Coxiella burnetti Highly pleomorphic and diverse collection of bacteria difficult to describe as a single homogenous group mammals and arthropods are usually natural hosts vary widely in severity self-limited mild illnesses to fulminant and life-threatening infections obligate intracellular bacteria Gram negative (although they don't Gram stain very well) non-spore forming bacteria Can be subdivided into 3 bio-groups spotted fever RMSF caused by Rickettsia rickettsii Rickettsialpox caused by Rickettsia akari Boutonneuse fever typhus Louse-borne (epidemic) typhus caused by Rickettsia prowazekii Murine (endemic or flea-borne) typhus caused by Rickettsia typhi Brill-Zinsser disease scrub typhus have a single taxonomic name: Oriential tsutsugamushi 3 major serotypes are Karp, Gilliam, and Kato. Epidemiology intimately related to each specific vector transmission ticks fleas lice Presentation History tick bite or tick exposure recent travel to endemic areas similar illnesses in family, friends, or pets (especially dogs) Signs & Symptoms early notoriously non-specific mimic benign viral illnesses RMSF incubation of 2-14 days following tick bite fever, headache, myalgias, confusion rash abdominal pain and diarrhea Rickettsial pox incubation of 9-14 days following mite bite red papule at site of mite bite subsequently develops into eschar fluctuating fevers, headache, chills, rigors, diaphoresis rhinorrhea, cough, sore throat nausea, vomiting, abdominal pain Boutonneuse fever incubation usually around 6 days eschar and necrosis at tick bite site known as tache noire ("black spot"), is pathognomonic acute onset high fever, headache, myalgias differs from other similar rickettsioses because of painful lymphadenopathy multiple eschars nuchal myalgia occasional sparse vesicular rash Louse-borne (epidemic) typhus abrupt onset 1-2 weeks after louse bite fever headache rash days 4-7 of infection spreads from trunk to extremities spares face, palms, and soles Brill-Zinsser disease milder form of louse-borne typhus Murine (endemic or flea-borne) typhus milder and shorter form of louse-borne typhus Scrub typhus incubation period approximately 1-2 weeks necrotic eschar at mite bite site enlargement of regional lymph nodes Evaluation Labs serology possible thrombocytopenia, hypoalbuminemia, hypotension, and coag defects assays against antibodies to rickettsial antigens can take up to 10-12 days to become positive immunofluorescence assay - considered the reference serologic method cannot determine causitive agent at the species level PCR testing and immunohistochemical staining help detect rickettsiae in blood or tissue for early diagnosis Diagnosis via clinical suspicion and serologic confirmation Treatment Lifestyle supportive therapy Pharmacologic doxycycline will treat all rickettsial infections highly effective and best outcomes if started within the first week of illness side effects - rare association with staining of teeth in children younger than 8 years because of low dose and short duration chloramphenicol alternative to doxycycline rarely used in United States because of adverse effects side effects - potential bone marrow toxicity