Rickettsia rickettsii presentation

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1. Don’t get Spots when you hike in the Mountains By: Melissa Vaughn Rickettsia rickettsia Rocky Mountain Spotted Fever

2. Case Study In early September, an 8 year old female from Tennessee, presented at the emergency room with a fever over 102 for at least two days. She complained of abdominal pain, nausea, diarrhea, and vomiting. The patient was sent home after a diagnosis of viral gastroenteritis. After two days when the patient didn’t get better her parents took her back to the emergency room with fever (unbroken), anorexia, irritability, cough, abdominal pain mimicking appendicitis, conjunctival injection , nausea, diarrhea and vomiting. Physical examination showed a petechial rash on the trunk, arms, legs, palms, and soles as well as hepatosplenomegaly .

3. Case Study Continued… Laboratory results included a WBC count of 11.4 x 10 9  cells/L; showing increase WBC’s. Thrombocytopenia (72 x 10 9  platelets/L), elevated aspartate aminotransferase (AST) of 179 U/L (Normal <43 U/L), elevated alanine aminotransferase (ALT) of 63 U/L (Normal <49 U/L). She was given intravenous doxycycline empirically for suspected Rocky Mountain Spotted Fever. The patient took three days to recover on antibiotics and continued antibiotics for 7 days and confirmatory tests came back positive for Rickettsia rickettsii . A confirmatory indirect immunofluorescence antibody (IFA) assay was performed and IgG antibodies reacted with Rickettsia rickettsii antigen in a serum specimen collected after second admission into the hospital.

4. Rocky Mountain Spotted Fever Etiologic agent is Rickettsia rickettsii Transmission is through a tick bite Vectors include: American Dog Tick ( Dermacentor variabilis ) Rocky Mountain Wood Tick ( Dermacentor andersoni ) Brown Dog Tick ( Rhipicephalus sanguineus ) Cayenne Tick ( Amblyomma Cajennense ) Rarely Lone Star Tick ( Amblyomma aureolatum ) Symptoms typically begin 2-14 days after a tick bite Fatality rate is approximately 20% or higher for untreated patients http://www.cdc.gov/rmsf/stats/index.html

5. Rickettsia rickettsii Intracellular bacterium Invades eukaryotic cells Pleomorphic, non-motile coccobacilli 0.3 μ m by 1.0 μ m and weakly gram negative Cannot grow on standard cell culture media Can grow in egg yoke of embryonated eggs and several monoclonal cell culture lines Acquires adenosine triphosphate from host cells Gimenez stain of tick hemolymph cells infected with  R. rickettsii    CDC http://pathmicro.med.sc.edu/mayer/rocky-bact.jpg

6. Geographical Distribution http://www.cdc.gov/rmsf/stats/index.html

7. Pathogenesis Tick bite Phagocytized into endothelial cells Replicate in the cell cytoplasm and nucleus Oxidative and peroxidative injury to cell membrane Leads to vasculitis Erythematous spots Microhemorrhages creating petechial rash

8. Pathogenesis continued… Pro-coagulant state Platelet activation Increased fibrinolysis Consumption of anticoagulants Resulting in thrombocytopenia

9. Virulence Factors Rickettsial outer membrane protein B ( OmpB ) – adhesion Endocytosis into the cell Phospholipase D and Hemolysin C Actin based motility by protein RickA Virulence reduced in the winter months Restored by Blood meal or exposure to 37 degree temperatures

10. Symptoms 2-14 day incubation period Fever, earliest sign typically above 102ºF Rash (typically occurs 2-5 days after start of fever) Headache (in adults less likely in kids) Nausea Vomiting Abdominal pain (mimicking appendicitis or other causes of acute abdominal pain) Muscle pain Lack of appetite Conjunctival injection (typically in kids) Diarrhea in about 25% of kids

11. Laboratory Findings Test Result Complete Blood Count Normal to Increased Platelets decreased Sodium Decreased or normal Hepatic transaminases Mild to moderate increase Serum albumin concentrations Decreased Serum creatinine Increased Blood urea nitrogen Increased

12. Diagnosis Immunofluorescent antibody assays Latex agglutination Enzyme-linked Immunosorbant assays Skin biopsy of rash spots for immunohistochemical staining Cell Culture?

13. Treatment Doxycycline is the DOC For all ages Adults 100 mg twice daily Children <99 lbs should receive 2.2 mg/kg twice daily Children >99 lbs should receive the adult dosage Duration 7-14 days Chloramphenicol can be used for those with allergies

14. Prevention Light colored clothing Long sleeve shirts Long pants tucked into socks Tick repellents Check for ticks Use tweezers to remove tick Keep areas free of high grass and brush

15. References "Rocky Mountain Spotted Fever (RMSF)."  Centers for Disease Control and Prevention . Centers for Disease Control and Prevention, 21 Nov. 2013. Web. 28 Apr. 2014 . Mahon, Connie R., Donald C. Lehman, and George Manuselis .  Textbook of Diagnostic Microbiology . Maryland Heights, MO: Saunders/Elsevier, 2011. Print . Mayer, Gene. "Rickettsia, Ehrlichia , Coxiella and Bartonella ."  Rickettsia, Ehrlichia , Coxiella and Bartonella . The Board of Trustees of the University of South Carolina, 15 Apr. 2010. Web. 29 Apr. 2014 . Woods, Charles R. "Rocky Mountain Spotted Fever in Children."  Rocky Mountain Spotted Fever in Children . Pediatric Clinics of North America, n.d. Web. 29 Apr. 2014.

16. Questions?